head gasket thickness-compressed

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j.d.duggan

j.d.duggan

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all right out there.I have been trying to find some real numbers on the felpro 8553pt head gasket compressed.I've found numbers from .039 to .054 and trying to calculate cr is going to be a little tricky with this gap.I thought you guys might have some real numbers from experience.thanks
 
According to some of the members on here... .045 to .048
 
j.d.duggan said:
all right out there.I have been trying to find some real numbers on the felpro 8553pt head gasket compressed.I've found numbers from .039 to .054 and trying to calculate cr is going to be a little tricky with this gap.I thought you guys might have some real numbers from experience.thanks
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Your guess. I got specs for Felpro Head gasket 8553pt
 
I use .050" but some reports are as in post #2. So use .048 and you will be as good as you are going to get. Being off by +/-.003" is going to change your CR results by roughly +/-.05 point.

The .039" is for the Felpro 1008 head gaskets.

Also, I add 1 cc to either the chamber or eyebrow volume to account for the volume in the gap between piston crown and cylinder down to the top ring.
 
BTW, OP, I just posted in your cam thread on what I get for static CR, which is in the low 9's. The one unknown is if you have 2 or 4 eyebrow pistons. Let us know what you get; what CR calculator are you using?
 
I,ve ran the numbers on two sights and I come up with 9.93x1 and 9.98x1,both seem high to me for pump gas.the #'s I,ve used are 4.090 bore,3.31 stroke,head cc 65,valve relief 6.6,head gasket .049,head gasket bore 4.17,deck -.013,the pistons are .013 out of holes and I have 2 valve reliefs in each piston.do these numbers look right to you or am I missing something?
 
Your numbers look good to me except for:
  • The chamber volume; I commented on the other thread that 65 cc is likely an NHRA minimum spec, and is not the typical production chamber volume which is usually in the 70-73 cc range
Re-run it with 71 cc chambers and see if you get in the 9.3-9.4 range.

Edit: 73 not 37 as the upper end of the typical range LOL
 
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j.d.duggan said:
all right out there.I have been trying to find some real numbers on the felpro 8553pt head gasket compressed.I've found numbers from .039 to .054 and trying to calculate cr is going to be a little tricky with this gap.I thought you guys might have some real numbers from experience.thanks
Click to expand...
.046 is what they measured when I pulled them off. I build engines sometimes I Mill pistons for quench and I'll just say this I set my Pistons up in my motor to come up exactly .046, the compressed head gasket thickness, and left only .030 in the chamber and clay checked .032 quench...piston rock ... I feel pretty confident in my findings, with that 8553 gasket...but how about felpro consistency? Will they all be that thick or thin? Hmmm as builders that's why we check.
 
j.d.duggan said:
what do you mean 70 -37 cc range? did you mean 71-77 ? I hope
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Pretty sure he meant to say 70-73cc. 10:1 compression is fine for pump gas as long as you have the correct cam to give a decent dynamic compression, around 8:1 DCR is a safe max for premium pump gas... IMO even with a .039" head gasket you'd be fine.
 
I was reading up on the same topic last night I found someone on another forum measured his before and after and it was .051 compressed and .060 new. So it crushed .009.
 
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I used the 8553PT's on my 408, measured uncompressed I got .052-.054. Obviously less after squeeze.
 
Today is the first since I read this thread iv had a change to get to my shop. I measured my 8553pt gasket im getting .056 new that's uncompressed.

20190214_140216.jpg
 
Maybe this makes it clearer, as in it varies...so whatever you got, I got he got, she got... don't mean **** other than a range. LOL

Expect to measure different....but consider it will compress about .004

Screenshot_20190214-105439_Samsung Internet.jpg
 
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MOPAROFFICIAL said:
LOL
If you can trust the .004 crush after reading the variation of .010 thickness ootb.
I still don't trust it, is all I'm saying.
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What I read says up to .009 after compression. Either way .05 gets me in the ballpark enough to get a fairly accurate scr number. +or- .004 isn't that big of a change. I know my particular gasket is .056 so i will just use that number - .005 for compression and roll with it haha
 
The 8553s I pulled off my 360 a few years back measured .042. Its a stock rebuilder type gasket, I don't think FelPro gives a crap if that particular gasket is off one way or another. If you want a consistent thickness gasket use a 1008, they are .039 compressed every time.
 
The fel pro head gaskets that come in the teardown kit measure .055" thick and 4.178" diameter after compression for a volume of 12.5 cc ....

Compression 7-1.jpg


Compression 7-2.jpg



As shown in the calculations section of my how to on checking compression on your engine:

How to Check Compression
 
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