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Lotus Europa Forums => Technical Articles and DIY tools and tips => Topic started by: Grumblebuns on Saturday,April 04, 2020, 05:02:51 PM
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Preface:
With all California universities and colleges ordered shut down due to the Covid-19 crisis, my engine rebuilding class was interrupted mid semester. The fate of resuming my engine rebuilding class remains up in the air since all schools will be shut down for the foreseeable future. I doubt that I will be able to reassemble my engine in the class setting but will have to do it on my own. Not wanting to waste what I learned in the first half, I'm posting my experience on disassembling the engine during the first half of the semester. Engine reassembly will have to wait untill the school administration decides when classes will resume, if it ever does. Anyway, this starts with the first installment of the first half of the semester. All comments, corrections and criticisms are welcomed.
Chronicles of a Community College Engine Rebuilding Class
This is a sub-story to the main return from the dead saga of my 74 TCS 3923R. The primary goal of writing this journal is to give a technical description of rebuilding a twink engine from the perspective of a novice engine builder with average mechanical skills. In terms of my personal mechanical experience with the twin cam motors, I’ve adjusted valve clearances, replaced a couple of water pumps and had one attempted bottom end rebuild which could only be described as a massive failure. Taking this class, I hope to do it right this time documenting my progress detailing all of my successes and screw ups in the process. A lot of time will be spent on the minor details that may be obvious to the professionals but were not clear to me at the time
I’m pretty fortunate to have two Community Colleges both offering a decent auto technology curriculum within 35 miles from me. For the coming Spring semester, I enrolled in an Engine Rebuilding class which happens to coincide with my long delayed plans to put 3923R back on the road. With the help of a fellow Europa owner, I managed to get the engine/tranny pulled out of 3923R in time for the start of the first week of class, Pics 1&2.
Week 1
Day 1- The instructor set the requirement that everyone had to work with a lab partner. I was fortunate to have a recently retired mechanical engineer and budding car guy in my class. Previously taking an Engine Machining class last Fall, I knew him and his work habits working with and getting to know him; we should be compatible partners. Class is two days a week, Mondays and Wednesdays, 08am-11am. Lecture is one hour with the remaining two hours for lab/engine work. Those students who can not bring in their own engines will work on school provided engines.The text used for the class is “AUTOMOTIVE ENGINES Diagnosis, Repair, and Rebuilding” by Tim Gilles, 7th edition. This will be my reference for general engine procedures. My guide in the twink engine rebuild is the Miles Wilkins book “Lotus Twin-Cam Engine” and the workshop manual.
Day 2- Loaded the twink engine into the back of my Yukon and delivered it to class.The instructor apparently does not like to use universal style engine stands to support engines; instead he prefers to use engine disassembly tables.His thinking is that the weight of the engine hanging off of one end will cause distortion of the block especially for long inline 6 engines blocks, thus his use of tables, Pics 3&4.
With my engine muscled onto the engine disassembly table, we begin with the engine disassembly process. To ensure stability, the first thing we did was to remove the casters from the engine cradle. In order to reduce the overall weight of the engine, I had previously removed most of the ancillaries at home prior to loading the twink engine into the back of my Yukon. With the short time remaining in the lab period, the only item we have time to remove is the valve cover and examine the camshaft and tappet assembly. I let my lab partner look over the engine, and ask questions. During Week 2, the plan is to remove the head and start the bottom end disassembly. I lent my partner a copy of Miles Wilkins book for him to review prior to Week 2.
Week 2
Day 3- The twink teardown starts. In order to ensure that parts are not lost as they are removed, cam/ crankshaft caps and bearings are placed in specific trays and labeled with photos taken as to numbers and orientation as they are removed. The first problem reared its ugly head when we tried to rotate the engine with the crank pulley bolt; the engine would not rotate.There is nothing we can do until the head is removed. We continued with the engine disassembly and the removal of the head per the Wilkins book. With the camshaft caps removed, we got the second “oh crap” moment. We noticed scoring on some of the exhaust camshaft journals and bearing shells. The scoring is deep enough to catch a fingernail running a nail across the journal. Grinding the journals is not an option since there are no cam bearings available for undersized cam journals. Plan of attack will have to wait till we revisit the head later in the semester. We continued on with the head removal with no further problems. With the head removed, we discovered the reason for the seized engine There was a line of rust on the bore about ½” high above piston #2. Water/antifreeze must have leaked into the cylinder during storage and caused the rings to stick to the cylinder bore. Further examination showed a thick crust of carbon on the tops of all the pistons. We sprayed PB Blaster in the rusted cylinder hoping it would free up the rings over the next couple of days. End of Day 3..
Day 4- Not much time for hands on engine work. Classroom lecture took almost two hour which left us less than an hour left to work on the engines in the lab. Good news was that the engine freed up with minimal force on the breaker bar and I couldn’t feel any scoring in that bore from the rusted rings. Although highly unlikely, we’ll magnaflux the bores to see if there is a crack in the cylinder bore which caused the rings to rust to the bore. Final task was to remove the Gilmer water pump pulley off the crankshaft using a small clamshell bearing puller. End of Day 4.
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This will be a great thread, Grumblebuns! Even though I don't have a TC motor, I'll be watching this.
I haven't heard of magnafluxing (which I understand is a magnetic particle test) a cylinder bore which means nothing and could be the best method of testing for a crack, but I wonder if pressure testing the block or die penetrant testing might be easier and cheaper. (I just did a search for "die penetrant testing" and I was directed to magnaflux.com! So Grumblebuns and I may be talking about the same thing!)
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Yeah, it's a shame that the Covid-19 outbreak cut the semester short. Your BDA motor is based on the Kent engine which is the same as used in the TC motor so the bottom end work should be applicable to you. We did manage to magnaflux the block which will be detailed in week 3 or 4 and it showed no cracks. Magnaflux involves running a hand held electromagnet over a steel or cast iron surface sprinkled with fine steel filings/powder. The magnetic field generated by the electromagnet will cause the filings to be attracted to the cracked area forming a visible line highlighting the cracked area. I should've taken a photo of the process. The instructor demonstrated the technique on a cracked cast iron head and it showed the crack in the combustion area in vivid detail.
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It sounds like that class was pretty good to get experience with doing magnaflux testing. I had heard of magnaflux testing for parts like rods and cranks but never blocks that I remember. I didn't realize it was so flexible and simple and apparently inexpensive. Good to know!
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Found this You Tube video on magnafluxing the block.
https://www.youtube.com/watch?v=4a6IazD8ZCE
https://www.youtube.com/watch?v=oQK1t8lGEK8
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Chronicles of a Community College Engine Rebuilding Class
At the end of week 4 the engine disassembly is mostly complete.Disassembled parts were put aside for later examination and and measuring.
Week 3
Day 5- The first part of the morning was spent working on removing the oil pan.Working carefully with putty scrapers, the oil pan came off rather easily after about 15 minutes of use of the scraper between the pan and block. With the pan off, we removed the retaining bolts and tapped the front timing chest cover off along with the water pump and the backing plate. We flip the block over to gain better access to the crankshaft bearing caps. In preparation for removing the oil pickup and return pipes next week, we attempt to remove the oil pump strainer basket. My original intent was to minimize the damage to the tube by removing the strainer and inserting a drill bit slightly smaller in diameter to the tube and remove it with vise grips. Unfortunately, in the process, we manage to break off two of the tabs holding the strainer to the strainer base plate. We stopped at this point to reassess our strategy on removing the tubes. This ended Day 5.
Day 6- With just the crankshaft, pistons and jackshaft to remove, we moved the block assembly to a universal engine stand I brought from home to continue the teardown. After noting and documenting the orientation of the both connecting rod and main crankshaft bearing caps we begin removing the connecting rod caps and pushing the pistons out of the bores. All pistons came out without issue and we set aside the bearings and caps with the associated con rod. We noticed that the connecting rods have a “FRONT” cast into the front of the rod to denote orientation for reassembly. We next start loosening and removing the crankshaft bearing caps and set the caps and thrust washers aside. The crankshaft is lifted out and set aside. With time running short, we decided to leave the jackshaft and oil pickup/return tubes for another day.
Pic 1 shows oil pan removed
Week 4
Day 7- Today being Presidents day, no class was held so I decided to order replacement oil pickup and return tubes. So, I read ahead in the Miles Wilkens book on removing the oil pickup/return tubes and jackshaft .According to the book, the two tubes are to be removed, discarded and new tubes installed. A phone call to Ken at Dave Bean established that new oil pickup tubes are NLA. My initial intention was to reuse the oil pickup tube and have a new tube as backup in case we damaged the original tube during removal. I go ahead and order the used oil pickup tube..
Day 8- We measure the height of both tubes above the bottom flange of the block for reference during reassembly and move the block outside in order to use a MAP gas torch to heat up the block around the oil tubes. The original plan was to stick a drill bit slightly smaller in diameter than the tubes in the tubes with the strainer removed to minimize the crushing of the tubes while using two vice grips 180 degrees apart to wiggle out the tubes after heating the metal around the tubes with the torch. Not wanting to break off the remaining hold down strainer tab we decide to remove the tubes without using a drill bit to minimize crushing the tube. Unfortunately the MAP gas gave out after only a minute of heating so we were stuck with trying to remove the tubes cold. With a little bit of wiggling, both tubes came out and surprisingly with minimal tooth marks on the tubes.We moved the engine back inside and started removing the last major component in the block, the jackshaft. We remove the two hex bolts, one Allen bolt securing the retaining plate and gently pull out the jackshaft. The block is almost bare with only the three core plugs and four oil gallery plugs left to remove.The instructor decides to use our engine block as a demonstration opportunity in how to remove core plugs to the class.The trick is to hammer one side of the core plug with a flat punch and pivot the plug so the opposite side can be grabbed with a vice grip and pulled out. The two smaller plugs on the side were removed as demonstrated. The third larger plug was in the back of the block and obstructed by the engine stand holder so it was left for us to remove. After removing the stand holder our attempt at punching out the last plug only forced the entire plug up against the back wall of #4 cylinder. There was only about ¼” clearance between the cylinder wall and the back of the rear core plug. We decided to hold off further attempts until next week. Day 8 ended by removing the oil gallery plugs.
Pic 2 Mostly bare block on Harbor Freight engine stand. Engine cradle will be removed later . Core plugs and oil gallery plugs have yet to be removed
Pic 3 Two of three smaller core plugs. The third larger core plug is on the rear of the block up against #4 cylinder
Pic 4 Class instructor demonstrating the proper method of removing core plugs. Use a medium flat punch to strike the inside edge of the plug with a heavy hammer. Ideally the plug should pivot around on its axis with one half of the plug sticking out of the hole
Pic 5 Unfortunately the plug failed to cooperate and it dropped into the cooling jacket. Retrieve it using a pair of vise grips or channel lock pliers
Pic 6 My lab partner attempting to punch out the second plug.He was more successful in his attempt. The plug pivoted just enough to get a pair of vice grips to wiggle the plug free
Pic 7 Rear core plug removed. We had a difficult time removing this plug. The plug is almost up against #4 cylinder wall, about ¼” clearance when inserted. In trying to punch out one side, we only succeeded in forcing the entire plug up against the cylinder with the edge of the plug about half way into the bore.We called the instructor to help us out. He used a flat punch to peen one edge away from the bore edge enough to pull the plug out enough to grab it with channel locks and wiggle it out. The danger was not to put any undue force onto the cylinder wall and cause possible damage.
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Good stuff, Grumblebuns! I know you're doing a full rebuild but I got to wondering how many miles were on your motor and what your bearings and cylinder bores look like.
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BDA, my TCS only has a tick over 67k miles on it. Preliminary visual of the bores show no scoring but crosshatch marks are very faint and there may be a ridge at the top of the cylinder though the pistons came out with no issues. Bore measurements shows excessive piston to cylinder clearance; appears that an over bore will be required. This is troubling for an engine with fairly low miles on it. Crankshaft journals have some very minor scratches which may come out with just polishing . Will take a closer look when the crank is examined more closely.
Weeks 5&6 begins the examination an measurement portion of the class. I'll have the actual measurements of the components then.
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67k miles on a motor certainly isn't much for one that seems as worn as that is. I would guess that the PO wasn't as rigorous with maintenance as he should have been.
I'm looking forward to your next installment!
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I'm afraid that the wear was not the fully fault of the PO but was probably caused by yours truly. Thanks for trying to deflect the blame. Back then I was pretty good at changing oil every 3k miles so I doubt oil maintenance was the cause. Some of you may remember the Weiand Ram Flow air filters available back in the late 70s and early 80s. Early in ownership I swapped the stock air filter system over to a Weiand foam style air filter. I'm surmising that the foam deteriorated over the years allowing some unfiltered air to get into the combustion chamber. Learned my lesson. I'm still pondering what type of air filtration system I'll be using when the engine gets reinstalled. There will definitely be an air box with a reputable filter routed via a cold air intake.
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Some of you may remember the Weiand Ram Flow air filters available back in the late 70s and early 80s. Early in ownership I swapped the stock air filter system over to a Weiand foam style air filter.
Can I join your club, Grumbles?
Back in the 70's I replaced the stock air filter for a 'Ramflo' foam one on my Ford Capri GT.
I thought the induction noise sounded cool!
It wasn't long before that caused the rings to wear badly and I had an engine rebuild on my hands.
The local shop immediately blamed the dry foam filter.
After the rebuild, it started blowing smoke almost immediately so I returned to the shop to complain. Apparently, the shop had 'expanded' the pistons - fairly common practice back then, if I recall. They took the engine apart a second time and found one piston with collapsed lands between the top two rings. All of the compression rings were broken into small segments so presumably they weren't gapped.
In later years I've used a Uniflow oiled filter and thought it was pretty good but, like you, I'll be adapting an oversized paper filter from a more common vehicle.
Apparently the 'Ramflo' filters are still sold.
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Grumblebuns:
While the bores may indeed be worn, care must be exercised in judging "excess" clearance.
Compare the measurement at the bottom of the bore (where there is no piston ring travel) to the upper portion where the rings travel.
How much are the ring end-gaps open when placed in the bores?
Some pistons are cam ground ( I don't remember if this applies to TC's). ....Piston diameter will vary depending on where measurements are taken, and will affect bore-piston clearance.
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Some of you may remember the Weiand Ram Flow air filters available back in the late 70s and early 80s. Early in ownership I swapped the stock air filter system over to a Weiand foam style air filter.
Can I join your club, Grumbles?
Back in the 70's I replaced the stock air filter for a 'Ramflo' foam one on my Ford Capri GT.
I thought the induction noise sounded cool!
It wasn't long before that caused the rings to wear badly and I had an engine rebuild on my hands.
The local shop immediately blamed the dry foam filter.
After the rebuild, it started blowing smoke almost immediately so I returned to the shop to complain. Apparently, the shop had 'expanded' the pistons - fairly common practice back then, if I recall. They took the engine apart a second time and found one piston with collapsed lands between the top two rings. All of the compression rings were broken into small segments so presumably they weren't gapped.
In later years I've used a Uniflow oiled filter and thought it was pretty good but, like you, I'll be adapting an oversized paper filter from a more common vehicle.
Apparently the 'Ramflo' filters are still sold.
Ah yes, those would be the culprits. I hope they've improved the quality of the foam element over the years if they are still selling them.
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Grumblebuns:
While the bores may indeed be worn, care must be exercised in judging "excess" clearance.
Compare the measurement at the bottom of the bore (where there is no piston ring travel) to the upper portion where the rings travel.
How much are the ring end-gaps open when placed in the bores?
Some pistons are cam ground ( I don't remember if this applies to TC's). ....Piston diameter will vary depending on where measurements are taken, and will affect bore-piston clearance.
I plan on posting how the cylinder bores and pistons were measured with my Weeks 5 & 6 write up this weekend. I would be interested in your evaluation of my methodology.
Briefly, for the cylinder bores, I used a Sunnen dial bore gauge to measure the bore for taper and out of roundness. Four points were measured at the bottom of the bore at end of piston travel and the top of the bore just under the ring ridge, 90 degrees apart. The pistons were measured at the widest part at the skirt area below the wrist pins. Being novices at this, I believe we were accurate in our measurements after getting several repeated readings.
It would have been nice to get ring end gap readings in the bores but in the classroom setting with only 90 minutes per day to work on the engine, time was too short to get to it. I will have all of the measurements in my Week 5 & 6 posting. I would appreciate your comments.
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Chronicles of a Community College Engine Rebuilding Class
Week 5
Day 9- We scratched our heads trying to figure out the best course of action in getting the last core plug out of the block. Our instructor came over and recommended using a small diameter flat punch and try to carefully peen over the edge of the core plug at the 9 or 3 o’clock position taking care not to gouge the hole in the block.It took several taps but the plug eventually pivoted over enough to grip and remove with a pair of channel lock pliers. One thing we noted after the removal of the core plugs was the amount of rust and sediment sludge inside the water jacket. We decided to clean the block in the schools parts washer to remove as much of the built up oil and dirt deposit covering the 40 year old engine. The cleaned block is almost bare except for the jackshaft bearings for which the instructor plans on using our block to demonstrate removing the camshaft bearings. With the engine disassembly pretty much completed, we now begin the measuring and inspection phase of the rebuild. End of day 9.
Day 10- The day started with the instructor using our engine block to demonstrate the general technique of removing the camshaft/jackshaft bearings from the block. The jackshaft runs on three bearings inside the block, the original camshaft for the OHV Kent engine. Not having the special camshaft bearing removal/installation tool specified in the workshop manual, the instructor demonstrates the procedure using the schools universal cam bearing removal/installation tool. The three bearings popped out easily and were marked and put aside. Bearing installation will be detailed later during engine reassembly. There are many YouTube videos on cam bearing removal if anyone is interested in the procedure. The photos show the cam bearing removal/installation tools used by the instructor. The jackshaft bearings are interference fit full round bearings. For the first time hobbyist it would probably be best to have a machine shop remove/reinstall the cam bearings. Installation is especially critical in getting the oil holes in the block aligned precisely with the corresponding holes in bearing shells. If your first attempt gets the orientation wrong, you risk damaging the relatively thin bearing shells by attempted removal and reinstallation.
The block can now be considered stripped, ready for measuring and cleaning. The first measurement was to check the roundness of each of the crankshaft bearing housings. After re-installing and torquing the main crankshaft bearing caps to 55 lb ft, the instructor demonstrated the technique using a dial bore gauge and measuring two axis about 90 degrees apart for each bearing housing. All bearing bores had less than 0.005” variance. Since the manual has no specific value for crankshaft bearing housing diameter we used the general go/no go criteria of 0.005” for the specification. Because of the relatively small diameter of the main crank bores, getting consistent reading was difficult. After many attempts we were successful. Actual values were all between 0.002” and 0.003”
Next the instructor demonstrated how to check the straightness of the crankshaft line bore alignment of the five bearing housings using a precision straight edge/bar and a feeler gauge to check for any gaps between the bar and the bearing bore. The general rule of thumb is that a feeler gauge of 0.0015” should not fit between the bar and the bearing housing. Unfortunately the smallest gauge that was in the tool box was 0.0020” which passed the criterion but we’ll have to recheck the straightness with the proper size feeler gauge. The roundness and straightness of crank bearing bores should be expected since this is a low mileage street engine that did not suffer any major overheating or catastrophic crankshaft damage.
The last measurement on the block is to check the cylinder bore for taper and roundness and a visual to determine course of action on the piston and rings.and ultimately cylinder bore size.The school has a Sunnen bore gauge and measuring fixture to obtain very accurate bore size to the nearest 0.0005”.To get accurate bore measurements, the block is placed in the schools honing machine and the cylinders are cleaned using a flex stone attached to an electric drill with coolant jets from the honing machine helping to clean the bores. With an acceptably clean bore surface, we took the initial measurements. Each cylinder was measured at four points to determine taper and out of round.
A1 - along the wrist pin axis at bottom of the cylinder at BDC, where there is little to no wear.
A2 - along the wrist pin axis at TDC, maximum travel of rings just below the ridgeline, area of most wear.
B1 - 90 degrees to the wrist pin axis, at BDC where there is little to no wear.
B2 - 90 degrees the wrist pin axis, at TDC maximum travel of rings just below the ridgeline, area of most wear..
The difference between A1 and A2 or B1 and B2 will show the amount of taper between the bottom of the bore where there is no wear and the top of bore where there is maximum cylinder wear.
The difference between A1 and B1 (bottom of bore) or between A2 and B2 (top of bore) will show out of round. With A1 and B1 being below the travel of the rings, little to no wear should be expected.
The following are the measurements taken of my cylinder bores:
Note that the stock cylinder bore size is 3.250”
Cylinder # -------------------- A1------------------- A2------------------- B1------------------- B2
----------------------------------BDC------------------TDC------------------BDC-----------------TDC
#1 3.2515” 3.2545” 3.2505” 3.2540”
#2 3.2510” 3.2560” 3.2515” 3.2550”
#3 3.2515” 3.2555” 3.2515” 3.2555”
#4 3.2515” 3.2550” 3.2505” 3.2535”
Amount of taper between TDC and BDC (difference between A1 and A2 and difference between B1 and B2). In both the A and B axes, the top of the bore is wider than the bottom.
Cylinder #1: A2 - A1 = 0.0030”/B2 - B1 = 0.0035”
Cylinder #2: A2 - A1 = 0.0050”/B2 - B1 = 0.0035”
Cylinder #3: A2 - A1 = 0.0040”/B2 - B1 = 0.0040”
Cylinder #4: A2 - A1 = 0.0035”/B2 - B1 = 0.0030”
Amount of out of round between TDC and BDC (difference between A1 and B1 and difference between A2 and B2):
Cylinder #1: A1 - B1 = 0.0010”/A2 - B2 = 0.0005”
Cylinder #2: A1 - B1 = 0.0005”/A2 - B2 = 0.0010”
Cylinder #3: A1 - B1 = 0.0000”/A2 - B2 = 0.0000”
Cylinder #4: A1 - B1 = 0.0010”/A2 - B2 = 0.0015”
Current general rule of thumb is 0.001” for max taper and between 0.002”-0.003” for out of round. The readings show the somewhat unexpected taper and wear for a vintage twin cam engine with “only” 65k miles although out of round readings appear to be within the allowable band. The Lotus workshop manual specifies a clearance between cylinder and piston to be 0.0030”- 0.0036” (with type C piston). We will measure the piston diameters in the next couple of weeks. End of day 10.
Pic 1
My partner is shown using the universal cam bearing removal/installation tool. The main tool is the short section consisting of a driver, expandable mandrel, thick “o” rings/rubber bands, and select washers that are the same diameter of the bearing.The short driver is used for the outside bearings.
Pic 2
Picture shows the long extension for the driver along with the box of different size extra mandrels.The long extension is used in conjunction with the short driver for the inside bearing.
Pic 3
Instructor demonstrating the use of a dial bore gauge in determining roundness of the crankshaft journal bores. There was some difficulty getting consistent readings due to the small size of the bearing bore relative to the gauge head.
Pic 4
A precision straight bar laid across the main bearing to check for bore straightness.
Pic 5
A feeler gauge is inserted under the bar at each bearing
Pic 6
The piston represents the cylinder bore illustrating the points of measurements of the cylinder bore. Black arrow is in the direction of the wrist pin and crankshaft, the “A” axis. The yellow arrow points in the direction of the “B” axis 90 degrees from the “A” axis.
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Thanks Grumblebuns! Another interesting day at school! My experience with this sort of thing was to give a block, crank, rods, and pistons to a machine shop and let them do whatever they do and expect them to know what they're doing. It's nice to get more insight into all the things they look at and how they look at it. It's usually more involved than you think!
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Finally got around to reading this thread start to finish. Very informative! Your descriptions and photos fill in a lot of gaps in my knowledge that the Miles book assumes the reader already knows. What a shame the Covid-19 outbreak cut the class short. Still, hope to be following this through reassembly. Keep up the great work Joji! :beerchug:
Tom
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I believe there is only one more week of class before the state imposed stay at home order was imposed. Kind of jumping ahead in the story, just after the order was announced the instructor allowed me to retrieve my engine block from the engine lab at school. Not knowing how long crisis this was going to last, I wanted to bring the block in to a machine shop for block cleaning and perform a professional inspection to confirm my classroom measurements. So the story will continue, stay tuned.
Joji Tokumoto
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Chronicles of a Community College Engine Rebuilding Class
Week 6
Unbeknownst to me at the time, I had no indication that the Stay at Home Order for the entire state would be issued by the Governor of California at the end of Week 6. I did not have a chance to discuss my measurements with my instructor and get his input before all formal in class lectures were cancelled.
Day 11- The lab day starts off with the instructor demonstrating a method for cleaning hard carbon deposits from the tops of pistons. His preferred method is to use a wire wheel on a bench grinder. He does stress that there are dangers to the body using this method. It takes great care and focus using this method but it is quick and effective. The technique is just to wire away the hard carbon crust but not get into the aluminum top of the piston. Also the wire wheel should never be used on the ring groove area. To clean the grooves, break an old compression ring in half and use the end to scrape off the gunk inside the grooves (Pic).
With all the measurements pointing to the block potentially needing a rebore, we magnaflux the head to confirm that rust in #2 cylinder was not caused by a cracked cylinder. The results are negative for cracks in all of the cylinder bores.With measurements and testing completed on the block we move on to measuring the pistons to determine piston to cylinder bore clearance.
The Wilkins book states that all production pistons are now C”’ type and give diameter according to original factory grading, from 1-4 in 0.0003” increments (3.2467-3.2470 to 3.2476-3.2479). I have no idea what grade my pistons are or their original diameters. Neither the service manual nor the Wilkins book specifies a gauge point to measure piston diameter. Falling back on the general rule of thumb, pistons were measured at the widest part of the piston, the skirt area ½” up from the bottom.
My stock pistons are Hepolite “C” type with the following diameters, average of four readings:
Piston #1: 3.2462”
Piston #2: 3.2464”
Piston #3; 3.2462”
Piston #4: 3.2468”
The service manual states a piston to bore clearance spec of 0.0030”-0.0036” irrespective of piston grade. These are the piston to bore clearances of my engine using the widest measurement.
Cylinder #1: 3.2545” - 3.2462” = 0.0083”
Cylinder #2: 3.2560” - 3.2464” = 0.0096”
Cylinder #3: 3.2555” - 3.2462” = 0.0093”
Cylinder #4 3.2550” - 3.2468” = 0.0082”
I don’t have the experience to know if the clearances we measured are way out of spec or is within the normal expected wear range for an engine with this much miles but
looking at just the amount of cylinder taper measurements, it appears that a rebore of my engine block is needed. Even taking into account the inexperience of the measurement takers, the consistency of the readings should not be discounted. I’ll have the instructor look over the data sheet to confirm our conclusion.
Visually to my inexperienced eyes, all four pistons look pretty undamaged. There are no stuck rings,or any major scratch or scrape markings. There appears to be normal scuffing on both the major and minor thrust areas with most of the scuffing along the major thrust (inlet) side.
I was hoping for a budget rebuild with the possibility of reusing the original pistons and just do a re-ring and re-hone the bore but apparently is not to be.This ends Day 11. About the only measurement left on the bottom end is the crankshaft. This ends Day 11. About the only measurement left to do on the bottom end is the crankshaft.
Pic 1 - The instructor demonstrating the use of a wire wheel with a junk piston to clean carbon from the tops of pistons. There is always the danger of the wire wheel catching the edge of the piston and throwing across the room, thus ruining the piston. Great mental focus is required using this method. Note that the connecting rod is kept installed to allow greater control of the piston. If my stock pistons were going to be reused, my plan was to use a chemical process to clean the carbon from the piston tops.
Pic 2 - Next four pictures show the condition of #1 piston. Again to my inexperienced eye, I see no signs of severe engine overheating or lack of lubrication as there are no deep scrapes or scratches, just smooth wear on the two thrust face areas. Picture 2 shows the rear view of the piston as it fits in the cylinder bore looking from the rear of the engine to the front.
Pic 3 - Picture 3 shows the front of the piston
Pic 4 - Picture 4 shows the left side, exhaust side or minor thrust side of the piston. The black dot indicates where the piston diameter was measured. Compare wear patterns to the right side
Picture 5 shows the right side, intake side or major thrust side of the piston. Most of the piston wear occurs on this side. On the top of the piston, the cutout for the intake valve is slightly larger than the exhaust cutout.
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I can't say that my eye is really any less experienced than yours, but that piston looks good to me.
Again, being inexperienced, I would prefer to chuck the piston in a vice and then use a wire brush on a drill but the carbon via chemical means makes more sense to me.
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Chronicles of a Community College Engine Rebuilding Class
Week 6
Day 12 - The instructor started the morning lecture by discussing crankshafts. Inspection, measurements and repair of the journals are covered during the classroom session. During the disassembly of the engine earlier in the semester, we did a quick cursory exam of the crank and there appeared to be no discoloration or deep scoring of the journals. There may have been some very light scratches or scoring on one or two of the main journals.I’ll have the instructor make an evaluation on the crank next week or so. The scratches are not deep enough to catch a fingernail and so I’m hoping a crank journal polish will be enough and not a crankshaft regrind..According to the instructor crankshaft journal grinding is a very specialized skill that not too many auto machine shops have the equipment or machine operator to perform.
During the lab session, the instructor plans on doing a couple of demonstrations. If there is enough time after the demonstrations, my partner and I will try to get the crank journals measured. The lab session is all about connecting rods. The first demonstration is the proper way to torque the end caps to the connecting rod without damaging or stressing the con rod beam using a dedicated fixture. Before the big end can be measured for roundness the end cap nuts have to set to the factory torque specs (Pic1).
The next demonstration is using the built in micrometer of the rod honing machine. The micrometer is set to the big end journal spec and the rod is set on the measuring pegs and rotated about 180 degrees in both directions.Note that the micrometer measures, within an accuracy of 0.0005”, any deviation from the preset nominal diameter of the big end journal, not the actual big end diameter of the con rod. Any deviation greater than 0.001” will require the big end to be resized which essentially grinds down the end cap a few thousands and the rod assembly re-torqued and manually honed in a connecting rod honing machine to achieve original diameter and maintain roundness to within specification (Pic 2).
With the end of the planned demonstrations, there is just enough time for my partner and I to measure the crankshaft journals. Each journal, both main and big end, are measured in four specific locations. We start at the front of the crank, normally where the crank pulley and keyway are located. Each main journal (5) and big end (4) are numbered sequentially from front to back for measuring purposes. For the mains the keyway is used as the reference point and designated as the 12:00 position. Each main journal is measured at the 12:00 and 6:00 o'clock position and the 3:00 and 9:00 o’clock which will determine roundness of the journal. To determine taper both the front of the journal and the rear of the journal are measured at the same four points.
The connecting rod journals are measured essentially the same way. The only difference is the location of the designated reference point. I believe we used the casting lines on the crank as the reference. These are the specifications per the workshop manual:
Main: 2.1255”/2.1260” (53.987mm/54.000mm)
Crankpin: 1.9370”/1.9375” (49.199mm/49.211mm)
These are our crankshaft journal measurement points.
Pt A = 12:00 & 6:00 position/front
Pt B = 12:00 & 6:00 position /rear
Pt C = 9:00 & 3:00 position /front
Pt D = 9:00 & 3:00 position/rear
#1 main journal - Pt A = 2.1259///Pt B = 2.1258///Pt C = 2.1256///Pt D = 2.1256
#2 main journal - Pt A = 2.1258///Pt B = 2.1259///Pt C = 2.1256///Pt D = 2.1256
#3 main journal - Pt A = 2.1256///Pt B = 2.1258///Pt C = 2.1258///Pt D = 2.1258
#4 main journal - Pt A = 2.1259///Pt B = 2.1259///Pt C = 2.1259///Pt D = 2.1258
#5 main journal - Pt A = 2.1257///Pt B = 2.1256///Pt C = 2.1257///Pt D = 2.1257
#1 crankpin journal - Pt A = 1.9370///Pt B = 1.9371///Pt C = 1.9371///Pt D = 1.9371
#2 crankpin journal - Pt A = 1.9370///Pt B = 1.9371///Pt C = 1.9370///Pt D = 1.9371
#3 crankpin journal - Pt A = 1.9369///Pt B = 1.9369///Pt C = 1.9370///Pt D = 1.9370
#4 crankpin journal - Pt A = 1.9369///Pt B = 1.9369///Pt C = 1.9370///Pt D = 1.9370
From the above reading for the mains, the journals are well within spec for roundness, taper and diameter. The crankpin readings are also within spec for roundness and taper but all of the journals appear to be on the low end of the spec. Journals 3 & 4 are slightly under the minimum specification. Re-measuring of the crankpin journals and consultation with the instructor will be required. This ends Day 12.
One day after Day 12, a stay at home order due to the Covid-19 outbreak was issued for all of California and the Community College immediately announced the cessation of all classes for the next two weeks.Anticipating that this could turn into a longer break, I immediately email my instructor to see if I can pick up my engine block. He designates next Monday as the only day students can pick up their equipment if desired. If I had thought ahead, I should have picked up all of the disassembled bits but only ended up picking up just the block and piston/rod assemblies which I then dropped off at a local auto machine shop not far from the school.I asked them to clean the block with their pyrolytic oven, jet wash the oil galleries, and re-measure the cylinder bores to double check our measurements.They also recommend shot peening the block to relieve the metal of any residual stresses.. Since the block needed a re-bore, I agreed. While the block is out with the machine shop, I am on the lookout for a replacement jackshaft.
Pic 1 & 2 - The con rod fixture is secured in a vise with the rod big end clamped securely but not tight in order to torque the end cap to the rod. The rod needs to be at correct torque for the big end measurement checks.
Pic 3 - The instructor is demonstrating the measuring micrometer of the rod honing machine.
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Another interesting post, Joji! I don't think it ever occurred to me that a journal might not be round or not cylindrical.
It's too bad your class was cut short!
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A bummer to be sure. The instructor is floating around the idea of finishing up the semester during the summer break all depending on the Covid 19 situation of course. My next posting will bring the engine block status with the machine shop up to date from their inspection. If the stay at home order is extended through the summer, I'll contact the instructor to see if there can be an exception made to allow me to pick up the the remainder of the engine components. I also have my 365 transaxle I left at the school. I was using their parts cleaner to clean up the casing and bell housing on the 365 which did a pretty good job of getting rid of 30+ years of dirt and oil crust.
The semester is essentially over; we took the final exam online a week ago. If worse comes to worse and the California university system is shut down for the rest of the year, I'll try to get my engine pieces and tranny back and install a spare TC motor I picked up a few months ago into 3923R and finish up its resurrection. I may decide to reassemble the motor on my own but I'll make that decision if and when I get to that point.
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I sure hope you guys aren't locked down through the summer much less for the rest of the year!
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Chronicles of a Community College Engine Rebuilding Class
Week 1, Covid-19 lockdown
When I dropped the engine block off at the machine shop the young kid at the counter immediately recognized the block as coming from a Lotus as they had just done an engine from a Lotus 7 not too long ago.Hmmm, I was thinking, this engine block may be good hands. I request that the shop re-measure the cylinder bores to double check our measurements taken at the class and ask what methods they use or recommend to clean blocks. He recommends doing a pyrolytic oven clean followed by shot peening the block. I also request a jet clean to follow up the oven clean to clean out the oil galleries. I pay a small deposit and I’m on my way.
I should note that the community college does have a pyrolytic oven to clean blocks and equipment to bore blocks.A new facility was also built to house additional equipment but again due to budget shortfalls,there was not enough funds to hook up power to the stored equipment. Any engine block cleaning that a student may need to have done will be up to the student to have done by a commercial shop. The school does have a couple of boring bars to bore out blocks and if needed I can use to over bore the Lotus block. The school has a Rottler computerized honing machine to complete the re-bore with the final finish hone and brushing. The lack of funding comes into play once again with the honing machine not having the tooling to hone out blocks smaller than the 4” bores used in the Detroit V-8s. So again any rebore of small displacement engines will be at the students expense at a commercial machine shop
During this waiting period, I need to use the time to locate a replacement jack shaft. During the engine disassembly earlier in the semester, we noticed a major problem with the jackshaft. Some of the helical teeth on the jackshaft for the oil pump gear drive had been broken off (Pic 1). It’s possible that some of the broken bits had traveled with the oil flow into the crankshaft and caused the light scoring on some of the journals. I found one of ebay for $175 which is a decent price seeing that a new one from Pegasus racing goes for around $400. I came close to hitting the “buy it now” button before I back out at the last second and decided to keep waiting for a cheaper one to show up. With my sometimes good luck,one did fall into my lap. I was visiting my machinist friend about making another run of high balance tube manifolds for me. He had recently retired from doing any machine work in his shop due to health reasons but a fellow machinist friend comes by on a part time basis to help out on work that occasionally comes in, like mine.Knowing that he had a lifetime of Lotus and FF parts collected over the years stashed in his shop, I asked him if he had any Kent engine jackshafts lying around. In the middle of our conversation, he suddenly asks me if I’m still interested in the Stromberg head I had asked about a few weeks back. At that time, we were in the engine disassembly period and I was looking ahead to the possibility that I may want to have a replacement head as back up in case there was an issue with my current head in the TCS. I made an initial offer which he thought was too low and that he told me that he would think about it. Apparently he had changed his mind in the intervening weeks.So I came out of that visit with a Stromberg head along with a usable Kent jackshaft, a set of Stromberg carbs and stock airbox out of an Elan.
Week 4, Covid19 lockdown.
I finally get a call back from the machine shop. They confirm the cylinder bore measurements taken by us during our lab session engine disassembly and recommend a 0.020” overbore for the block which I agreed with. I saw no need to go with a larger bore size thus leaving room for additional overbores when needed. I call Dave Bean Engineering and a couple of days later a package shows up at my front gate with a set of four 0.020” over forged JE Pistons/wrist pins/ring set along with a set of cam bearings for the jackshaft and new bushings for the connecting rod small end.. Seeing what is required with the installation of the jackshaft bearings, I elected to have the experience of the shop install the cam bearings for me.
This pretty much brings my story up to the present, just waiting for the machine shop to tell me that they are done with my engine block. The unknown is what the Community College will do for the upcoming semester. The instructor is talking of re-commencing and trying to complete the class during the Summer session but I suspect the class will be cancelled and graded as Incomplete. As California starts to slowly re-open its business’ and institutions, there should be an opportunity to retrieve my engine components and start my engine reassembly albeit on my own without an experienced mechanic to directly ask for help and guidance.
Pic 1
A jacked up jackshaft. .Damage probably occurred during one of the oil pump removal and reinstallation. Unsure or don’t remember how the damaged gear teeth affected oil pump operation. Will have to disassemble the oil pump to see if the internals can be cleaned up prior to reinstallation. If not a new oil pump will be ordered
Pic 2
The included Strombergs, also probably from an Elan ( bottom airbox is Europa). Notice that on the Elan the airbox inlet faces in the opposite direction from the Europa.This may be a good alternative for a cold air style induction system if taking air from the bottom of the fuel tank location since there is no modification to the Europa airbox required. Problem is that a stock Elan airbox will probably be hard to locate.
Pic 3
Replacement jackshaft. I’ll have the machine shop polish the journals
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Nice write up, Joji! Hopefully you'll be able to continue your class soon. Keep us informed about future progress.
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Chronicles of a Community College Engine Rebuilding Class
Week 20, Covid19 lockdown
I receive notification from the class instructor that the school administration has allowed limited resumption of the engine rebuilding class. On the first day back, the limited resumption timeline of the class was laid out. The class will meet for the next four days from 8am to 4pm. With parts that I will need to order and my cylinder head still not touched, there was no way that I could get my engine back together properly in the allotted time. My only choice was to request a withdrawal from the class and retake it next Spring. I spent the remainder of the morning collecting and cleaning my parts in the school’s parts washer. The final task was to load my cleaned parts into my Yukon and finally leave the campus.
Being left high and dry with the most important part of the rebuilding process yet to come, I’m scrambling to find space in two packed garages to begin the reassembly process on my own without technical assistance available. I’ll keep posting my progress in case my experience helps anyone else contemplating or needing an engine rebuild and the process involved.
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That's too bad you were caught unawares! Are there other measurements you have to make before you can start building?
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The next step in the rebuilding process would have been to check the crankshaft clearances. With the machine shop still in possession of my engine block and spare crank, I'm stuck. If the crank journals need to be ground, that will be an additional few more weeks. I believe one of the con rod big end journals was at the lower end of the spec on the crank held captive at the school. The status of the spare crankshaft that the machine shop is inspecting is still unknown. I'll drop off the original crank with the machine shop to get their opinion of its usability.
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Left to my own devices
Chapter 1, The cylinder head
With all of the engine components back in my possession, most importantly the head and crankshaft. I started looking for an engine builder to inspect and work on my cylinder head. Following the recommendation of a machinist friend, I contacted and dropped off my head with long time Lotus specialist, John Kouba.. He did an initial check of the head and found nothing obviously out of the ordinary. The head I brought up to John Kouba is not the original head on 3229R. This replacement head was installed back in the 80s when the original head was too badly overheated to remain in use. The head appears to have been previously skimmed but was still within specification for head thickness.
All the head needed was his standard head refurbishment procedure. This was good news as no extra money will be needed for additional repairs to the head unless something unexpected comes up during the disassembly process.
Around two weeks later I get an email from John stating that my head is finished and can be picked up. I made the two and a half hour drive up to John’s place and he went over the work that was done to the head. During the disassembly of the valve train components are examined as they were removed. The only item he found out of the ordinary was some minor pitting on the exhaust cam lobes. I exchanged it for one of his spares. Once the head is completely disassembled, his standard refurbishment procedure is to clean and degrease the head and oil galleries and blast the head with walnut shells to decarbonize the combustion chambers. Valve guides, valves, and buckets were replaced with new replacement parts as a matter of course with this engine builder.
With new buckets/cam followers installed and there is still the slightest discernible play between bucket and the cam follower bore, then new sleeves will have to be installed. This procedure is described in the Miles Wilkins book. Obviously this extra machine work increases the final cost of the head rebuild. If the valve seats are in good condition, they are re-cut for a fresh three angle valve job. Valve face to seat contact is checked and the valve is lapped in. Next, valve spring pressure and height is checked and shimmed as necessary to specification. New cam bearings are installed and if requested, which I did, valve clearances are set on the bench. The basic “valve job'' is complete.
I’ve scanned and attached the total cost that John Kouba charged me for the head work, rounded down to $1000 even for payment. My head work may or may not be typical and final costs will depend on the amount of additional machining work required to repair any issues. It’s possible that some costs can be reduced by the owner setting the valve clearances otherwise expect to pay your local engine guy some big bucks for a basic valve job. The extra $100 on the invoice was for the exhaust camshaft exchange and I had John inspect my spare Weber head at the same time. Additional items that will need to be ordered are eight exhaust studs, valve cover cork gasket and eight Seloc valve cover washers. I plan on reusing the original valve cover locknuts. The engine builder supplied the exhaust manifold brass lock nuts free of charge.
I added another invoice for the inspection and rework for a Weber head I've had for over 30 years for reference.
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My first thought was that $1000 seemed like a lot but that included a lot of parts. $85/hr shop rate seems very reasonable to me too. It looks like you’re in good shape for your next step!
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I agree that the shop rate this builder charges is pretty reasonable. I don't know how much he marks up his parts but it can't be that much on these small items. However all of the operations do add up for the total cost. I added another invoice for another head I had my builder refurbish at the same time as the Stromberg head for reference. In this case, the buckets were not replaced and the valve clearances were not set.
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Left to my own devices
Chapter 2, The bottom end
The same day that I returned home after picking up the cylinder head from my engine builder, I found a message from the machine shop on my answering machine that my engine block and crankshaft are done and can be picked up. I was hoping to get additional details of what work was done to my bottom end components when I stopped by the machine shop to pick up my engine block the next day. Unfortunately the person who did the work on my engine was not at the shop that day to answer my questions. All I could go by was the discussion we had when I dropped my engine off to be worked back in March.and the invoice of all the work done.
Block cleaning - pyrolytic oven cleaning
jet spray oil passages
shot peen block
Magnaflux block
Surface block
Bore cylinders 0.020” oversize
Install jackshaft bearings
Line hone the block main bearing housings
Resize connecting rods big ends
Remove/re-install new wrist pin bushings
Magnaflux crankshaft
Clean/polish crankshaft
Polish jackshaft journals
Measure crankshaft main and connecting rod journals
Supply standard size main and connecting rod bearing sets
Total cost - $1083.72
Even in the middle of taking an engine rebuilding class, I was still surprised at the number of operations required to rebuild the bottom end. The individual operations themselves are not that expensive but add up all the operations required and the total cost can be an eye opener and my rebuild was relatively uncomplicated.
Dropping the block off with the machine shop, I was fairly sure that the cylinders would have to be bored out and the machine shop confirmed my measurements taken during class. The crankshaft was another matter however. My measurements indicated that the main journals were all on the low end of the specification but within the band. The connecting rod journals indicated that all were also in the low end of the band but one journal was approximately less than 0.001” outside the low end of the band. When I dropped the crankshaft off a few weeks later, I asked the shop to double check my measurements. Their measurements showed both the main and conrod journals to be on the low end but still inside the band so no grinding of the journals to the next undersize was required; defer that for the next rebuild. That news saved me additional charges.
With all of the refurbished engine components back in my hands, the final step prior to starting the reassembly process is to do a complete wipe down of the block and crankshaft with rags and solvent and blow out the oil galleries with compressed air.
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Are you going to try to get up with the machinist to get more details about what was done?
My understanding is that shot peening is used to relieve stress and to strengthen areas by “compressing” the outer layers of the metal. Do know where they shot peened the block?
Great write up!
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As much as I would have liked to talk to the guy who did my engine block, I won't have time to at least three weeks. I suspect that would be too long for the guy to remember the details of what he did. Unfortunately there was no data sheet with all of the as left measurements of block and crankshaft. I don't have the tools to measure the cylinder bore with any accuracy but I can measure the crankshaft journals to verify their work.
Relieving stress in the metal is also my understanding for shot peening the block. I believe they shot peen all surfaces on the block. They warn that cylinder bores will have to be bored out after shot peening due to the damage caused by the balls. When I start the reassembly of the engine, I'll post pictures of the block as received after it was cleaned and shot peened. I'm anxious to begin the reassembly but will have to wait three weeks until I can start due to other pressing issues.
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I've heard of shot peening rods but I've never heard of shot peening a block. Interesting...
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Chapter 3, Reassembly preps, painting and final cleaning
For main reference and guidance during the engine reassembly process, I will be mostly following the sequence of steps as Miles Wilkins outlined in his book “LOTUS Twin-Cam Engine”. For general automotive good operating practices and procedures not covered by Wilkins, I will reference Tim Gilles text book, “AUTOMOTIVE ENGINES - Diagnosis,Repair, and Rebuilding” 7th edition, used in my engine rebuilding class. An additional reference consulted was “Tuning Twin Cam Fords” by David Vizard.
These are the sequence of steps I used in prepping my engine block for reassembly. There are more detailed explanations for each section.
- Install the core plugs and coolant jacket drain plug. Core plugs should be installed before the block is mounted to a universal engine stand. This is especially important for the rear plug since the mounting plate for the stand will restrict access to the rear of the block.
- Install the oil gallery plugs.
- Paint the block at this time since there is less stuff to mask off.
- Do a final cleaning of the crankcase surfaces.
Plugging the holes:
Who would have thought that after watching multiple Youtube videos, installing core plugs could be so difficult. Ideally, in watching Youtube videos, pounding in core plugs is simply smearing sealant on the plug or hole (sealant use seems to be optional with some guys) and pounding the plug in with a socket using a few hammer blows. Unfortunately in my case, it didn’t work out that way and a detailed step by step sequence of the painful experience follows.
There are three core plugs on the TC engine block, two 1-⅝” diameter plugs on the exhaust/left side and a larger 2” plug at the rear. I had ordered core plugs from one of the Lotus vendors but didn’t ask if they supplied steel or brass. I was sent a set of stainless steel plugs. Wilkins in his book vaguely mentions using a “suitable drift” by which he means sockets for core plug installation .For the 1-⅝” plug, I found that a 1-¼” or a 30mm socket will fit perfectly on the plug outer rim and a 1-⅛” socket will give a good fit inside the 1-⅝” plug. For the 2” plug, a 1-½” socket will fit on the plug outer rim but unfortunately I didn’t have a socket that will give a good close fit inside the 2” plug. All of the sockets I used were the standard short non impact style which will in the end turn out to be one of the problems contributing to my failure (Pic 1). A set of deep well impact sockets would have been a better choice.
For sealants, Wilkins mentions using Wellseal. Most of us probably don’t have a tube of Wellseal available so a search for an equivalent sealant is required. The purpose of the sealant is to seal against tiny gaps in the metal to metal interference fit between core plug and casting. In a low pressure, moderate temperature application such as a car coolant system, I believe any gasket type sealer should be more than adequate. A search of the internet shows that Permatex Aviation Form- A Gasket Sealant Liquid, Permatex Grey, Hondabond/Yamabond/Kawabond/Threebond sealants and various Loctite products are equivalents used by the British car community. I should mention that Permatex Indian Head Gasket Shellac used by some appears to be very similar looking to Wellseal. For my use, I chose Hondabond 4 due to its availability at my local Honda motorcycle dealer.
The final item to consider is the hammer. It has to be heavy enough but still be controllable when swinging. All I had available was a 2 lb dead blow hammer which gave underwhelming results .A heavier dead blow hammer would have been better from the start. I also used a 5 lb mini sledge hammer at the latter stages in desperation.
With all of my tools and plugs assembled, I started my preparations for the first plug which was the 2” stainless steel. Because the Kent block is relatively light, it is important to have the block resting on a solid surface such as a concrete floor or a heavy work table to take the impact of the hammer blows. After a quick visual check of the holes in the casting for any damage or imperfections to the hole surface before proceeding, I performed a light touchup of the sealing surfaces to remove any corrosion with fine sandpaper, and a final wipe down with alcohol of both the plug and the hole edge. A light coat of sealant is then applied evenly to the plug edge. The plug is squarely aligned to the hole, and the socket is placed evenly on the plug rim. Because the socket is a standard short socket there is no way to safely hold the socket in place during the hammer strike. As a result the socket would skate off the plug and the plug bouncing off the block after every hammer strike. After a few more attempts with the same result, I decided to stop and regroup. My next brilliant idea was to try to shrink freeze the plug with canned air. Using a half can of Dust Off to freeze this time, the smaller 1-⅝” stainless steel plug, got the same result using both the 1-¼” and the inside the plug 1-⅛” socket. The plug would not go in. At this point, I decided to give up on using sockets and decided to rent a bearing/ seal driver kit from my local Advanced Auto parts store. I also decided to give up on using the stainless steel and use brass plugs for my next attempt. So again starting with the smaller 1-⅝” brass plug and using the adapter disc with flat side down against the plug and my steel 5 lb mini sledge hammer, I successfully drove in the plug with about three moderate blows. I completed the job with the remaining two plugs. The last hole in the water jacket is for a threaded ¼” threaded drain plug, guessing possibly BSP threads, just behind the rear 1-⅝” core plug (Pic 2). Apply a bit of thread sealant and tighten snugly with a 9/16” socket.
I should explain that the decision to abandon the stainless steel core plugs was not to malign the plug itself but that I didn’t want to cause possible damage to the rented tool with the potentially harder SS plug. The cheap bearing/seal driver set that I rented was all aluminum, both the adapters and the driver/handle. I felt that the harder stainless would form dents in the adapter face and I didn’t want to pay for any damages. I plan on another attempt using the SS plugs for my next rebuild with the right tools in hand. This will include correct size deep well impact sockets and/or steel adapters of the correct sizes, a steel handle/driver and a 4 lb or heavier dead blow hammer. For those wanting to use brass plugs, a rented seal/bearing driver kit will work as well.
One last caution for those wanting to buy the plugs from other sources, be aware that the plugs come in different depths. The 1-⅝” plugs used in the Lotus Twin Cams are also used in older small block Chevys. The ones supplied for the SBCs are about twice as wide in depth and if used in the Lotus will protrude further into the water jacket. Plug depth is especially critical for the 2” plug which has only has about ⅓” of clearance between the #4 cylinder and the rear casting wall.
With the water jacket sealed up, it's time to seal off the oil galleries holes. You trust that the machine shop did their job of cleaning the block but it doesn’t hurt to verify. Before screwing in the threaded plugs, I ran a brush through both sides of the high pressure oil galleries and blew out the holes with compressed air. A tiny bit of fine dust blew out, possibly some left over corrosion. There are three ¼” pipe threaded holes for the high pressure oil supply side galleries. One threaded hole and one small unthreaded hole at the rear of the block (Pic 3), two threaded holes at the front of the block (Pic 4) and one tiny (possibly 1/16” pipe) threaded hole also for the high pressure supply side on the right side of the block (Pic 5). All have pipe sealant applied to the threads and gasket sealant to the small plug before installing. Depending on the source, the oil gallery plug pipe threads are either NPT, BSP, or NPTF depending on who you want to believe. I have not personally verified the thread type.
Installing this small approximately 7/16” push in oil gallery plug (Pic 3) was the final stumbling block to overcome in completing the block plug installation. As with the coolant core plugs, I had a difficult time installing this plug which is not normally removed by most engine builders since it doesn’t plug a pressure side oil gallery. It plugs a hole in the oil drain from the head back to the sump and is not pressurized. In my case the machine shop removed the plug as is their practice for block cleaning. This is not a problem since there are replacement plugs for that hole; the problem I had was getting the correct sized plug from the vendors. I measured the oil return hole on my block at 0.423”. It is possible that this particular hole size may not be standardised for all Kent blocks, thus the variation in the plug sizes supplied by the various vendors.
These were the plugs supplied by the two Lotus vendors:
Dave Bean - EP0461, Soft Plug 29/64” (0.453”). As delivered, the plugs were measured at 0.480”.
RD Ent - A026 E 6034, Core Plug 7/16” (0.437”). As delivered, the plugs were measured at 0.452”.
Burton lists a 7/16” plug in their catalog
My first attempt in trying to drive in the plug was with the ones supplied by Dave Bean. I used a small socket on the outside edge of the plug which resulted in a totally destroyed plug. With the second plug, I used a steel rod on the inside cup of the plug. This resulted in the steel rod punching a hole in the plug after a couple of hammer blows..
Knowing that the plugs supplied by Dave Bean had fitment issues, I ordered two plugs from RD Enterprises. I measured the plugs when they arrived and saw that they were smaller in diameter than the ones supplied by Dave Bean and initially thought that they may fit. There is no chamfer around the hole in the rear of the block so getting the plug centered and straight is a bit difficult. For the first RD Ent plug I used the head of a ½” bolt about 5” long against the outside edge of the plug to hammer the plug into the hole. As with the Dave Bean plug, the edge of the plug started to deform before the plug would start to go in.
With three plugs destroyed I decided to regroup and do additional research on the internet. I found a company in the UK that supplies core plugs and has a core plug conversion chart that gives dimensions of holes in fractions and decimals. According to the chart, there should be a 0.010”-0.015” interference fit between the hole and plug. Their plugs are automatically oversized for the holes for proper interference fit,
https://enginecoreplugs.com/conversion-chart/.
From my measurements of the plugs received from Dave Bean and RD Enterprises, both of their plugs are grossly oversized for my hole and the reason I had problems trying to install them. With my oil gallery hole measured at 0.423”, the plug that should be a match will be for a 27/64” (0.422”) hole. I found a company in the US supplying all sizes of core plugs and ordered a batch of 27/64” plugs in brass.
https://freezeplugfactory.com/
When the 27/64” plugs arrived, I measured the plug diameter as 0.427” which gives a 0.004” interference fit. Even though less than optimal, I decided to use these plugs since the plug will be under almost no pressure from the oiling system. The plug drove in fairly easily with a few moderate taps of the hammer. I’m wondering if the steel version of these plugs may give a tighter fit. With the last plug installed, this completes the block prep. Next step, painting the block.
Finally ,what are these three left over open holes on the block(Pic 3 & 4)? There are three holes still left unplugged at this stage of the bottom end reassembly process. The first one previously mentioned is the hole for the oil pressure gauge fitting at the front right side of the block which will be fitted after the engine is put back into the car. The second and third holes are at the front of the block. The second hole is for the head oil drain gallery back to the sump. This hole is normally not plugged and will be blocked when the timing cover backing plate and gasket are installed. The third hole is for the coolant bypass passage from the head back to the water pump suction. This hole aligns with a corresponding hole in the backing plate and the timing chest cover.
Pic 1 - These are the sockets I initially used in my initial attempts.The biggest problem in using the shallow standard style sockets is the inability to control the sockets in place on the plug when striking directly with a hammer plus the possibility of shattering on impact. A safer and better method would have been to use an extra long deep well impact socket that fits snugly inside the plug well without being too tight. An alternative would be to fabricate a steel or aluminum handle/driver to fit inside the plug well.
Pic 2 Left side view of block
(2) 1-⅝” core plugs
(1) block coolant drain plug
(0) oil gallery plugs
Pic 3 Rear view of block
(1) 2” core plug
(1) supply side oil gallery plug
(1) 27/64” oil drain plug
Pic 4 Front view of block
(2) supply side oil gallery plugs
(1) head oil drain opening
coolant bypass passage
Pic 5 Right side view of block
Supply side oil gallery plug to opposite side oil gallery
Oil pressure gauge threaded connection
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Picture page
Pic 1 - These are the sockets I initially used in my initial attempts.The biggest problem in using the shallow standard style sockets is the inability to control the sockets in place on the plug when striking directly with a hammer plus the possibility of shattering on impact. A safer and better method would have been to use an extra long deep well impact socket that fits snugly inside the plug well without being too tight. An alternative would be to fabricate a steel or aluminum handle/driver to fit inside the plug well.
Pic 2 Left side view of block
(2) 1-⅝” core plugs
(1) block coolant drain plug
(0) oil gallery plugs
Pic 3 Rear view of block
(1) 2” core plug
(1) supply side oil gallery plug
(1) 27/64” oil drain plug
Pic 4 Front view of block (picture text reads rear in error)
(2) supply side oil gallery plugs
(1) head oil drain opening
coolant bypass passage
Pic 5 Right side view of block
Supply side oil gallery plug to opposite side oil gallery
Oil pressure gauge threaded connection
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Great write up, Grumblebuns! Having never installed my own freeze plugs, I found it pretty interesting.
When trying to install a plug with a socket, did you try using an extension so you would have something to hold on?
The thread pitch for NPT and BSP are different (except for 1/2”) and NPT are tapered threads while BSP threads are straight. Straight threads mean there has to be a flat surface for a sealing washer or similar. I would expect plugs in cast iron to be NPT.
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Great post, lots of good stuff in there. I've done core plugs myself on both engines and they've been plain mild steel ones, I could imagine Stainless being harder to use.
The ECP site is a very good find, bookmarked for "just in case" reference !
I know it's more work, but at some point it would be great to get these individual posts all together in a single PDF file as a sticky on the Tech. Article site. We can all read manuals but the "I made a mistake/had trouble here" is something we only learn through experience and well worth sharing.
Brian
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Great write up, Grumblebuns! Having never installed my own freeze plugs, I found it pretty interesting.
When trying to install a plug with a socket, did you try using an extension so you would have something to hold on?
The thread pitch for NPT and BSP are different (except for 1/2”) and NPT are tapered threads while BSP threads are straight. Straight threads mean there has to be a flat surface for a sealing washer or similar. I would expect plugs in cast iron to be NPT.
I've looked into BSP which seems to be the global standard. According to this site, https://tameson.com/thread-standards.html, there is BSPP for parallel threads and BSPT for tapered threads. I imagine back in the 1960s when the Kent engine was developed, Ford of England would have used the BSP standard. Just speculating on this and can't know for sure until someone measures the pipe plugs.
Use of an extension may have helped with the brass plugs with standard sockets. With the SS plugs, only a bigger hammer and a steel driver would have worked in my opinion. My fault for not using the right tools for the job.
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Great post, lots of good stuff in there. I've done core plugs myself on both engines and they've been plain mild steel ones, I could imagine Stainless being harder to use.
The ECP site is a very good find, bookmarked for "just in case" reference !
I know it's more work, but at some point it would be great to get these individual posts all together in a single PDF file as a sticky on the Tech. Article site. We can all read manuals but the "I made a mistake/had trouble here" is something we only learn through experience and well worth sharing.
Brian
Brian, I'm using Google docs to write this journal and currently I'm up to 60+ pages. When I get done, I'll have a PDF file for reference
Joji
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Was not aware of tapered BSP! That does complicate things!
I have to use an angled adapter so my heater valve will clear my headers. It is 1/4” NPT and fits as expected so I’m led to believe that engines in the ‘60s and ‘70s still used the NPT standard.
I’m looking forward to your finished document!
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The TC engine was developed a few years after the Kent engine. Wondering why Lotus decided to use NPT standard for the heater valve threads.
FWIW, the Elan forum has a ton of postings on oil gallery plugs and the difficulty in removing them. The Australian company Elantrickbits states that the oil gallery plugs are 1/4" BSP.
I have a couple of spare plugs to measure once I get a thread gauge for pipe threads.
http://elantrikbits.com/lotus-elan-blog/oil-gallery-plugs-remove-from-twin-cam-engine-block/
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Curiouser and curiouser! The heater valve screws into the head and Lotus may have bucked a trend so they could use an existing, inexpensive heater valve.
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I heard back from my engine guy and he states that he always used NPT plugs, so as you said, it gets curiouser and curiouser.
Someone has probably figured this out in the past, just have to find the info.
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Grumblebuns, were you ever able to get this going again?
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The project has been on a bit of a break due to a major remodel of my garage for final inspection. All inside work is done, and the new roof should be installed by end of next week (I was shocked by the cost of plywood decking). Currently, I'm in the process of moving the cars and parts back in and doing a bit of cleaning reorganizing. I plan on resuming my engine rebuild within a week or so and continue the chronicling of the rebuild. It's been almost a year since my last post.
Joji Tokumoto