Twin Cam Engine Build Head/Head Gasket

[Sherman Kaplan]

I'm in the process of rebuilding a Twin Cam engine and have a few questions.   I'm an amateur and this is a retirement project.

1.   In ordering parts I accidentally ended up with two head gaskets.  One is from RD Enterprises and looks like a composite gasket while the second one is from SJ Sportscars and looks to be the original style copper.  Please see the attached pictures.  Any suggestions as to which is better to use?  This will be a street engine to stock specs. It has been bored .030 over.    According to the Miles Wilkins book if I go with the copper gasket it is suggested to coat  it with wellseal.   Any thoughts on this?  I do have a tube so I can do it.   I have also read on the Lotus Elan site where it was recommended to use copper head gasket spray instead of wellseal.  Very confusing?

2.   I ordered the Dave Bean cartridge water pump.   I splurged and went with the gilmer drive.   The gilmer pulley does not have a timing mark.   I have used the original pulley and lined up the timing mark to TDC.   I then put the new gilmer pulley on and temporarily put a paint mark where I  think it lines up with TDC on the timing chest.  I'm sure that when file a mark on the pulley it won't be 100 percent accurate.   Is there any better way to do this?    I'm trusting that if I don't move the crankshaft that I will be OK when putting the timing chain sprockets on the camshafts.

Also, just an FYI I trusted that the casting would be identical to the original so I assembled everything, using The Right Stuff  rtv on the front cover.   After everything was together I tried to turn the timing chain and found it was binding and would not turn the jackshaft.  I took everything apart and found the casting was a bit to thick so I had to grind off a small amount.  Put everything back together and now the timing chain turn the jackshaft just fine.  I learned a good lesson to check and double check everything before final assembly.

3.    Any hints on installing the head?  I know about cutting the heads off of two old head studs and using them as a guide, but I can't see how to do this as the head has to be shifted to the right to clear the timing chain damper.   I have a video from the UK and the professional mechanic says he could never get the stud idea to work.   

4.  Most important question:  I was speaking with a professional mechanic today who is very familiar with the Twin Cam engine.  He strongly suggested that I turn over the final assembly of the engine to a professional.  He said he won't touch them and referred me back to the machinist who did my machine work.  The machinist assembles twin cam race motors so knows his stuff.   I've already assembled the bottom end and the head has been rebuild by John McCoy at Omnitech.   Am I in over my head or is this something an amateur can do? 

Thanks in advance for advise.

Sherman

[BDA]

I would use the copper head gasket because you have both but I doubt in the street situation, it probably doesn't make much difference. Back in the stone age when I was racing my MG Midget, the competition head gasket was a requirement - the street gasket was worthless. The competition gasket, as I remember, was copper around something like asbestos (this was in the mid '70s). Your copper gasket, however it's made will be better than the street gasket, but then the street gasket is perfectly appropriate for a street engine. As I say, since you already have both, use the best. As for gasket treatment, I used to use a Permatex red spray gasket treatment. It seemed to work fine but I really don't have enough experience to quantify how good it was. I would say that, first, everybody has their favorite stuff. Second, Wilkins' book was written quite a while ago but that doesn't mean that his suggestions should be ignored - they are perfectly acceptable. Third, I would consider a more recent suggestion of a more recent product if the suggestor is reliable. I wouldn't sweat it. Permatex is a good brand. I would use either a Permatex product or the wellseal stuff, but somebody with recent successful experience is well worth listening to.

Marking TDC on your water pump pulley should be pretty straight forward. The keyway on the crank should point up at TDC. I haven't built a TC motor but I think the more important thing is to pay attention to the orientation of the flywheel since that's where you'll set your ignition timing.

The Right Stuff is, from what I've heard, is actually THE RIGHT STUFF. Also good on you for noticing that you needed a little casting relief.

As I said, I've never built a TC motor. I understand that all the sealing surfaces around the timing chest are a problem. Timing the cams requires some care and knowledge, and building OHC motors are a little more complicated than a rocker arm  motor too. I might ask your machinist to see what he says. I'm sure he'd want to do it, but he should be honest enough to tell you if you're over your skis. Maybe you could work a deal where you build it and he checks it. The workshop manual seems pretty detailed. If you understand all that, you should be able to build it yourself, but having a guy check your work (especially since it's your first time building that sort of motor) is very valuable.

Hopefully, someone who knows more than I will chime in.

Good luck and let us know what happened!

[jbcollier]

1)  Generally composite gaskets hold up better.  I believe the RD gasket is designed to reduce the TC's propensity to leak oil.  How do the thicknesses compare?  I got in the habit of spraying my head gaskets with Permatex High Tack from my days working on Peugeot engines.  Never had cause to regret it.

2)  You need to find TDC properly using a piston stop and dial gauge.  That way you can mark the pulley 100% accurately.

3)  You mean, "head bolts" not "head studs".  The problem is that you need to keep the head gasket from moving after you have lined everything up and applied the sealers.  Cut two down so that the will protrude just enough to hold the gasket in place.  Cut a slot in them as well.  Once the head is in position, fit the other head bolts, unscrew the two guides using the slot and withdraw then using a magnet.

4)  Twin Cam engines are not a good choice for your first engine build.  I'm a little concerned that you didn't know how to accurately find TDC.

You have fit new pistons, has the deck height changed?  The block is shiny, was it decked?  Any fancy head work?  Larger valves?  Shaved? Cams?   High compression and high cam lifts usually mean claying the pistons and checking actual clearances.  Some builds require assembling and disassembling multiple times to make sure things are spot on.

[EuropaTC]

Hi Sherman,

My last head gasket replacement was a couple of years ago now and I used the lower of your two gaskets, the copper one. I'll try for a couple of your questions;

1. Wellseal. It's an old product and I've used it in the past, in fact the current Europa HG was assembled with it. I used Wellseal simply because the guy I bought my parts from used it in his customer restorations and he gave me a small jar for free, but it was messy to use as I recall.   When I did the Elan head recently I used a modern Hermetite product, I can't honestly remember what it was other than I read the label and it seemed suitable for the task.  TC engines are known to leak, so perhaps it's belt'n'braces from Lotus ?

2. TDC - You should be able to get somewhere near from the keyway but personally I'd use a dial gauge on the piston crown as John suggests. It might not be any more accurate than going by eye, but using a gauge is one potential variable removed.

3. Using guides to locate the head makes life so much easier. I didn't use cut-down head bolts, I used some rod which I'd threaded the last half inch. Then you can make them any length you want and they're easy to remove. Without something like that to secure the gasket in place it's very easy to land the head at an angle and slide the gasket, unless of course your choice of assembly "goo" is very, very sticky.

4. Can you do it ?  Well, I don't know because I've never met you, but I'll go against the grain and say there's nothing complex in the TC engine.  The bottom end is a Ford engine, the same as found in millions of cars and rebuilt by home mechanics the world over. 

Where it seems to frighten people off is when you get to the cylinder head. If it had a cast iron head with pushrod valves no-one would bother but having a chain drive twin OHC where you adjust the clearances using shims, then you get sharp intakes of breath.  I'm amazed your pro mechanic wouldn't entertain building one, in fact it makes me wonder if he's ever actually done so and is just going along with the myths ?

Anyway, if you're new to the engine, or engine builds in general,  the first thing I'd suggest is to buy the Miles Wilkins book on the TC engine. It's mainly centered about the Elan variant but apart from the inlet cam, it holds good for the Europa TC. 

The second thing is to take your time and if anything feels hard to assemble then before you force it, check you're doing it right. These are simple engines (even with twin overhead cams - look how many have them these days) and should slot together without undue force. 

I don't know if you have the cams already shimmed and fitted to the head or not but having the pistons/valves in the wrong place when you drop the head on is probably the easiest area to slip up on. On a new build I'd put the head on and then the cams but I've also just replaced the HG leaving the cams in the head. Either will work but double check the cams are at TDC when the engine is and that you're not getting piston/valve contact before you tighten those head bolts !

Brian

[Pfreen]

I have pulled the head on my tc twice in the past year.  I originally purchased The RD head gasket for my first rebuild.  However, it was twice as thick as the Payden copper/steel gasket .025 crushed for the Payen and approximately .050” for the RD gasket.  On my engine, that would lower the compression ratio from 10.29 to 9.53.

After I found the RD gasket was thicker, I did not think I could get the Payen gasket since RD didn’t stock them.   So I bought a Cometic gasket.  The oil and coolant holes did not line up well at all so I sent it back.

So, I call Dave Bean and they had the Payen gasket for a very modest, $30.

So, I used the Payen gasket both times.

The Payen gasket has some smaller coolant flow holes.  I don’t know the exact reason but they are that way for a reason.  I did not want to take a risk.  The Wilkins book shows the Payden gasket as does the Lotus workshop manual.


The Payen gasket has some kind of a clear plastic like soft coating on it, presumably for sealing.  I did not use any gasket goo or copper spray on it.  In fact, I have had the head off of my tc 4 times since 1986 and have always used the payen gasket as is and have never had a leak.  I think making sure the head and block are meticulously clean and flat are the keys to success.

As far as rebuilding the engine, take it slow, get and study the Wilkins book and learn a lot.  Just double and triple check your valve timing with a degree wheel and you will be fine.  Carefully bar the engine over to insure there is no interference.

My biggest problem with rebuilding twincams is the front cover/water pump assembly.  Just follow the Wilkins book.  I would also suggest pressure testing the engine with 10psi of air to insure there are no leaks prior to installing the engine back in the car.  Just make some plugs out of pvc, 1.25” radiator hose and hose clamps.

[Sherman Kaplan]

Thanks for everyone's response. I should have been more clear on my question regarding the pulley. I know to use a dial gauge to find TDC. My question was more how to accurately mark the pulley.  Years ago I changed a crankshaft pulley on an MG and didn't think I marked it accurately enough, but I guess I did as I've never had a problem in timing the engine.

I have rebuilt one MG engine (that still runs nicely) and have attended several MG engine rebuild seminars.  The most recent one was put on by John Twist who is the Miles Wilkins of the MG community.  My machinist is willing to answer questions so with his help and with the help of this group I'm going to give it my best shot.   As Pfreen said I will double and triple check everything.

Sherman

[jbcollier]

If the engine is the same as before (valves, cam, compression ratio, etc) then a rebuild is a straight forward process.  It's when you change things (warmed up cam, bigger valves, higher CR) that you need to carefully check for proper running clearances.

Please correct me if I'm wrong but aren't there TDC and firing marks on a TC's flywheel?  Much easier to see when the engine is in place and much more accurate.  Mind, you have to fit the flywheel in the right position.

[BDA]

You are correct, JB. I alluded to them in my post. IMHO, the flywheel orientation is much more important than the relationship between the jackshaft and the crank. Since the jackshaft sprocket is in the timing chest, I don't think the relationship between it and the crank sprocket is important at all. I don't have a TC so if somebody knows better, please enlighten us.

[4129R]

I cannot see why knowing TDC on the pulley very accurately is needed.

The flywheel, IIRC is held with 6 bolts, so the flywheel has to be fitted correctly so the timing marks line up with the gearbox, where the window will show the exact timing marks.

I would make sure the timing marks on the flywheel are clearly visible so that when setting up the ignition timing with a strobe light you can see exactly what is happening.

[Pfreen]

The tc flywheel is marked for tdc and I think through 30 degrees in 10 degree increments.  The pointer is the bell housing which is as-cast and is not “perfect”. It’s typically good enough, for ignition timing, but when doing the valve timing, I would attach a degree wheel to the front of the crankshaft, obviously setting it by determining tdc with a dial indicator.  After that, you can determine how accurate the front cover, crank pulley timing marks are.  The front cover has timing marks cast in it and the crank pulley has a “v” notch mark to indicate crankshaft position. 

I use a white paint pen to mark the flywheel sothat you can see the marks with a timing light.