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Old 01-11-2009, 11:22 AM
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Which head gasket & how much will compression raise?

Block is 10066034 4.00" bore, & 64cc iron heads are 14096217. Compression ratio on the engine currently is 9.1:1, & compressed head gasket thickness is 0.028".

I'm looking for a head gasket that will compress to something like .015 that's suited for iron / iron. I'm asking because I'd like a part number on something people have tried, and is true.

I'd also like help figuring out what the new compression ratio would be with the thinner gasket installed.

_Brett

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Old 01-11-2009, 11:29 AM
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Several companies make thin shim gaskets in stainless & coated steel etc..
GM, Detroit, MrGasket, Felpro etc.. For compression ratio try here.>>>>>
http://www.kb-silvolite.com/calc.php

Felpro-1094= .015"-Embossed
MrGasket-1130-.018-.020" Embossed

Last edited by SSedan64; 01-11-2009 at 11:37 AM.
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Old 01-11-2009, 11:48 AM
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Quote:
Originally Posted by SSedan64

Felpro-1094= .015"-Embossed
My problem with the felpro gasket, is it's cut out for a 4.100-4.155 bore I believe, and that in itself will lower my compression and decrease power won't it?

I was hoping to find one that will fit exact with the bore, or is that not how it goes?
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Old 01-11-2009, 11:54 AM
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Some gaskets have smaller bore size but you'll have to search or call around for specs. Check here, they'll make anything you want.
http://www.cometic.com/custom.aspx
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Old 01-11-2009, 11:59 AM
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I wouldn't try to raise compression with a gasket, the stock shim style already have problems with factory compression...running thinner than that is just asking for problems.
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Old 01-11-2009, 12:06 PM
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You'd only gain about .25CR going from .028" to .015" gasket, say 9.15-9.4CR
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Old 01-11-2009, 12:38 PM
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Quote:
Originally Posted by 4 Jaw Chuck
I wouldn't try to raise compression with a gasket, the stock shim style already have problems with factory compression...running thinner than that is just asking for problems.
I've read conflicting opinions on this issue. I'm not sure where the problem is, if it's improper installs that are blowing out, or if it's certain blocks that have water too close to a cylinder due to people running thinner gaskets overbore .030 or more and the heat transfer causes a weak point or what.

I did read that if Iron heads that are true and square, they are a better choice for a thinner head gasket due to the material being the same as the block, and the rate at which the materials expand and contract isn't going to be a factor in performance of the head gaskets like it would be for someone running aluminum heads.
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Old 01-11-2009, 12:59 PM
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Just reminding everyone that we have this relevant wiki article: Head gasket.

I don't think it addresses the specific question in this thread, but, please feel free to update it with any additional perspective that can be gained from this discussion. Just click the "edit" link next to any of the sections in the wiki article, and edit from there. Thanks.
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Old 01-11-2009, 01:05 PM
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Quote:
Originally Posted by 5_speed
Block is 10066034 4.00" bore, & 64cc iron heads are 14096217. Compression ratio on the engine currently is 9.1:1, & compressed head gasket thickness is 0.028".

I'm looking for a head gasket that will compress to something like .015 that's suited for iron / iron. I'm asking because I'd like a part number on something people have tried, and is true.

I'd also like help figuring out what the new compression ratio would be with the thinner gasket installed.

_Brett
I would suggest you sit down with a hand calculator and the formulas for doing static compression ratio and manually crank out the differences on a sheet of paper.

You will quickly find that going from a .028 inch thick gasket to a .015 inch thick gasket has about the same effect on compression as does peeing in Long Island Sound to watch the water level go up. In other words it's a lot of exercise for what at best is a tiny and insignificant gain. Add to that, the extra thin gaskets are very sensitive to surface flatness and finish of the block deck and the head.

Bogie
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Old 01-11-2009, 02:11 PM
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That was funny, and I somewhat tend to agree with you, I think I may have been misunderstood. I'm not trying to raise my engines compression in effort to make more power by utilizing a thinner gasket. I'm removing the heads to have them machined and I'll have to replace the head gaskets anyway.

After much research, I concluded that a thinner gasket would work well for my application being all iron w/ stock bore.

Side note: While pouring a bottle of Dasani into a lock may not have a visual impact, it is still raising the water level. Then again, this is a 5.7L engine were talking about, not a 20 million cubic yard channel of water.

I wanted to know if there is a head gasket that compresses to .015 and is 4.00" bore that is fit for stock type applications, but looking through all my parts catalogs and discussing it on here has yielded an outcome of custom demand. I'll just go with the 1094's if that 1/10 of an inch isn't going to have a negative impact on longevity of the gasket. Given I torque the head properly, I don't think I'll have any issues.

As for asking how much the compression would go up, I was only curious


All in all, great advice gang, thanks again for the expert advice
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Old 01-11-2009, 02:30 PM
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You need to watch the distance from the piston to the head and maintain at least .040". This is what determines the gasket thickness, not desired compression ratios, etc.

Summit sells thin copper gaskets for about $ 120.

Then you have to determine valve/piston clearance, (you milled your block and heads), notch pistons if necessary, and work from there on compression ratio.
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Old 01-11-2009, 03:04 PM
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Any advice on how to take the measurements from piston to head, and open valve to piston?
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Old 01-11-2009, 03:11 PM
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measuring piston to head...

Hi,this has been chewed over many times,heres one more time,take some modeling clay. about 1/4 inch thick,put it on top of piston,install gasket,install head. turn over engine at balancer,NOT with starter motor.,take off head,take a razor blade,cut clay in half,measure thickness. do the same to measure the valve to piston clearance.
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Old 01-11-2009, 03:27 PM
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Quote:
Originally Posted by 5_speed
Any advice on how to take the measurements from piston to head, and open valve to piston?
Ya what Bob said, but that is pretty darn hard to measure with a micrometer when it gets that thin.

or just measure the block deck (head gasket surface) to the piston with a micrometer centered over the piston pin.
You can even use the depth stick of a dial caliper if you are diligent,

or even lay multi-layered feeler gauge on the piston until it feels level with the block deck. Just keep swapping the various layers until you are satisfied with the feel.

obviously the piston must be clean. Somebody was going to say it
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Old 01-11-2009, 04:02 PM
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Thanks gang, this is shaping up to one fine day!
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