TR2/3/3A Head Gaskets and Shaved Cylinder Head

What have I got myself into now? :emmersed:

I pulled my head to clean out the water and inspect the tappets, cam etc. I decided I should measure the thickness of my cylinder head after reading more about shaved heads, particularly sp53’s thread titled “shaved heads” and observed a fellows car that had just blown his head gasket and was explaining to me why it happened. here's the background: I bought my used head 5 years ago from a guy who was a racer and said it was a good one that had not been milled much, at that time I was not very educated and I didn’t give it much thought taking his word that it wasn’t a big deal. I took the head to a machine shop and had it rebuilt with all the best stuff, alloy valve springs, manganese bronze inlet guides and stainless steel ex valves I got from Ken G at British Frame. Now I'm learning more about what I don't know and spending more time and money on just the Cyln head. I now have a small collection of head gaskets too. A copper one that is .0321 thick, a supposedly completion gasket produced by Lucas and another one that I got in a kit somewhere. Yes, I am getting deeper and deeper into this quagmire and I need to get out!

Here’s where I am now: My head measures 3.208 and the preferred range is 3.325 to 3.33 so I am about .117mm to .122mm out of the preferred range (short). I think my options are to purchase a “thicker” head gasket, either copper or steel to make up the difference but what thickness or go with what I have and hope for the best? Or should I try to measure the head volume and calculate the compression ratio as Kas Kastner states in his book “how much (compression) is too much and how much do I have now? The process for completing this calculation described in his book seems a bit involved and requires purchasing a $75.00 burette and I need to read the chapter a few more times to understand it.

My question is what are your thoughts, all I really want to do is get the car back on the road and drive it I have lots of stuff left to do but this is an important detail I think! I did put in the larger pistons, 89mm and did a bit of upgrade to the cam thinking that it would be nice to have a little "pop" in the car. At this point it is getting a lot more complicated than I was originally thinking it would be plus time is marching along so a quick fix is tempting. However I really do not want to have to buy high octane and expensive gas and I don't want to have to do more work later on because I took a short cut and was impatient. Am I over thinking this? Would I regret just putting on a .032 copper gasket I have and get on to getting the car back on the road without going through the exercise of calculation my compression ratio? Attached is a photo of my head gasket collection!



Thanks!
Dorn

I think you may be overthinking it.

It is almost as easy to change a head gasket on these cars as it is to change the water pump...so I would lean towards "use what I got", and if you can't live with the compression, then find a thicker head gasket. Just keep track of what you are putting on, so you have a reference in case you want to change later.

Higher compression makes an engine rev faster and feels all around better. Considering you are starting with an engine that had 8:1 compression, and premium gas readily available now days will support up to about 11:1, I really don't think you have anything to worry about.

Depends on what else was done to the head, IMO. The combustion chamber design was primitive at best, and grinding .100" or so off just makes it worse. I tried running a head with about that much off and no other changes, along with 87mm liners, some years ago, and it was not happy at all on the best pump gas available around here. And that was with a stock head gasket that only crushes to around .060". Might have been something funny about that block and crank, though, since with a .010" gasket I could see the outline of the chamber on top of the pistons.

Remember, Triumph recommended 95 (research) octane even with the original 8.5:1 CR. If I've done my math correctly, just going from 83 to 89 will bump that up to around 9.5:1. And using a rough estimate of 6in^2 for the combustion chamber opening, milling 0.1" will bump you up to over 11 even with a stock head gasket.

You don't need an expensive burette to CC the heads, an ordinary disposable syringe will do. About $6 at the drug store (ask the pharmacist and explain why you want it), or if you have a friend that works in the medical field, they can probably give you one. Or there are cheaper burettes available as well, eg
https://www.hometrainingtools.com/b...ee=2&fep=596&gclid=CKDC9O-kgswCFUZrfgoduokL3A

I've learned my new word for the day. Burette. Never heard it before but now I know.
Marv

All the guys before me know more about this stuff. My opinion would be to get different stock head just because I find it difficult enough to get theses motors to idle down and run well, but again you said you made some other performance upgrades, so I am back to not sure.

Have y'all tried to buy a burette lately? I couldn't find anybody that would sell a new one. One distributor even claimed they had to submit names for sales to the DEA. Don't know if that's true, but I couldn't get one to save my life. Finally found a company going out of business that sold to me.

Maybe it's me...look like a cooker or something!?!

On high performance engines I would religiously match the chamber cc's and calculate the compression to 4 digits. From all that work I can vouch that cc'ing a head is slow work. I still think it would be faster to just put this street engine together and see how it does...especially since you have several gaskets. I can change a head gasket in about 2 hours...I used to spend 2 days cc'ing a head!

Or...since you know it's shaved and about how much...Marv, Randall, do these gaskets work alright if you stack them?? If so, you could just stack a couple .060" ers and get close to stock compression.

CJD said:

Or...since you know it's shaved and about how much...Marv, Randall, do these gaskets work alright if you stack them?? If so, you could just stack a couple .060" ers and get close to stock compression.

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Ummm, I was thinking about that too, is that a crazy idea? I'd put the two copper gaskets in with a good sealing copper coat gasket sealant. I don't think I can change my head in 2 hours though, maybe I get better if I keep doing it over and over. A new stock cylinder head is expensive and I have too much invested at this point to o in that direction. There is a company that makes different thicknesses of gaskets for racing. However there is some skepticism about how effective they would be for my street application. I leaning towards just putting it back together and seeing what happens. Decisions decisions?? https://www.headgasket.com/index.h

My approach would be (will be when I get back to that point again) to make the combustion chamber mods outlined by Kas Kastner (if they haven't already been done). Bring the CR back down a bit, improve power, reduce octane requirement, and very likely reduce fuel consumption. With those changes, you might have a chance of being able to run on pump premium.

As far as stacking gaskets, I have no idea. But the factory didn't go that way (they actually offered a kit to reduce compression ratio, but it included a steel plate to go between two gaskets, plus an extra thin steel gasket) so I'm guessing there is at least a potential problem. The flame front temperature runs well above the melting point of copper, and more copper exposed means it is going to get hotter.

Plus, the quench area (between the top of the piston and the flat part of the head) is an important factor in engine design, too much clearance can reduce efficiency (meaning more fuel for less power) and, at least according to some sources, increase the tendency to knock. Eg,
https://www.hotrod.com/how-to/engine/1311-ideal-quench-height/

CJD said:

Have y'all tried to buy a burette lately? I couldn't find anybody that would sell a new one.

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You can get them at any good racing supplier. Summit sells the kit with burette, stand, blank off plate, etc. The cheapest is $125, though. I just checked on Ebay and Jegs has one with a syringe for $20. Search for "head cc kit". Drug stores sell inexpensive plastic syringes that can be quite large for flushing, rinsing, etc. Check the shelves where they sell ear products or ask the clerk. I needed a very tiny syringe for dividing up flea medicine I bought in bulk (for the dogs, not me) the pharmacist just gave me one, no charge.

Dennis