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Chronicles of a Community College Engine Rebuilding Class
Grumblebuns:
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.
BDA:
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!)
Grumblebuns:
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.
BDA:
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!
Grumblebuns:
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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