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Former Super Moderator
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Discussion Starter #1
Head gasket just started leaking anti-freeze on the right side so they need to be replaced. I've always been chasing the dreaded pinging issue by backing the timing off a ton, but still get it. Does anyone make a thicker gasket that would drop the compression a tad to help?? I'm not finding anything locally.
 

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Bear would be the guy to ask on that. What thickness gasket are you running now? I'd be leery of any gasket over .060 thick.

My concern is losing quench in the combustion chamber. Quench, or squish area is the flat area on the top of the piston that's almost level with the top of the block deck. It must have a corresponding flat area on the deck surface of the head to qualify as quench.
If you look at a combustion chamber, you will see these flat areas, and they will have the volume of the actual combustion chamber between them. When the piston is compressing the mixture, as the piston nears the head, the flat areas on the head and piston come together and force the mixture from those areas to "squish" into the chamber, where the spark plug and burning mixture reside, so you achieve a more complete burn.
The quench area also runs cooler than the rest of the chamber / piston. These lower temperatures are where the "quench" comes from.
When properly designed, the quench areas can have a tremendous effect on the quality of combustion, and allow higher compression ratios. That is why chamber design is so important and why Pontiac machined their combustion chambers instead of leaving them as cast. Unfortunately we don't have access to the high octane fuels they had and combustion chamber technology has vastly improved over 50 years.


Have you considered putting the iron heads on the shelf and running some D-port aluminum heads?
 

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Cometic will make them for you. They're pricey though. Most of them vendors who sell Cometic can also order them in custom thicknesses.

Yes, if you're right on the edge a thicker gasket can help with a detonation problem. A thicker gasket will increase minimum chamber volume and lower your compression ratio. However, there are some "costs". That thicker gasket also puts the piston quench pads farther away from the head surface at TDC, and this will reduce "quench" in the engine -- less turbulence in the chambers = more tendency for the air/fuel to separate = decreased combustion efficiency = less power. It's also possible that it won't help with the detonation problem because that decrease in turbulence also tends to increase the probability of getting 'hot spots' in the chambers, which promote detonation. All of which Alky said - better than I did. :D

However.... if you're in a pickle with a detonation problem and aren't in a position to be able to address it with different pistons or different heads, the gasket solution just might be enough to help you. An engine that makes a little more power isn't much use when its guts are on the ground in a puddle of oil... :D

Do you know where you're at now with it, compression ratio wise?

Bear
 

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64-67 Expert
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Rukee, you are running basically the same engine I am in my '65. There are two solutions: Run race fuel/av-gas/TEL-130 mixed with premium, or install some aluminum heads. I've been running boosted fuel in mine for years, and because of that, don't drive it much. I've also been contemplating the expensive switch to aluminum heads. Thick gaskets are not a good way to address the problem, IMO....they ruin the quench as Bear stated and you end up with lower compression, pinging, hotter running, and lower performance. Plus, the thick gaskets are more fragile than the thin ones. You MAY be able to install some '67-later bigger chamber iron heads on your engine if your cam isn't too radical and you have the piston-to-valve clearance. The valve angle is different on '67-up heads, and the valves can hit the pistons on a '66-earlier engine.
 

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I have used dual steel head gaskets for years, I have had no issues. I did this to lower compression, The motor runs great on 91. I have done this on RAIII and RAIV.
 
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