360 compression
- Thread starter ike61
- Start date
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.040” to compensate for the felpro gaskets.
Professor Fate
Push the button, Max...
Factory steel shim head gaskets were about .020 compressed thickness. And according to:
I got specs for Felpro Head gasket 8553pt.
The Fel-Pro 8553 ranges anywhere from .046-.057 uncompressed, with the compressed figure being .003-.004 under that.
That means you would have to pay to have anywhere from .023-.034 milled off your heads to maintain your 8.7:1 compression ratio.
Machine work ain't cheap, so unless you're married to those gaskets I'd just get a pair of Mr. Gasket 1121G (.028 compressed thickness) to get you back in the ballpark.
But remember, it ain't just the head surface that will need to be milled- you'll need to either have the intake surfaces of the heads or the intake manifold gasket surfaces cut too, just to keep everything lined up. So you'll be paying for a minimum of four cuts, not just two.
*Edit- @Syleng1 's suggested .040 cut ain't a bad idea if you're having them cut anyways- a little extra compression at that low of a CR is a good thing.*
I got specs for Felpro Head gasket 8553pt.
The Fel-Pro 8553 ranges anywhere from .046-.057 uncompressed, with the compressed figure being .003-.004 under that.
That means you would have to pay to have anywhere from .023-.034 milled off your heads to maintain your 8.7:1 compression ratio.
Machine work ain't cheap, so unless you're married to those gaskets I'd just get a pair of Mr. Gasket 1121G (.028 compressed thickness) to get you back in the ballpark.
But remember, it ain't just the head surface that will need to be milled- you'll need to either have the intake surfaces of the heads or the intake manifold gasket surfaces cut too, just to keep everything lined up. So you'll be paying for a minimum of four cuts, not just two.
*Edit- @Syleng1 's suggested .040 cut ain't a bad idea if you're having them cut anyways- a little extra compression at that low of a CR is a good thing.*
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That's impossible to know without measuring chamber volume, and deck clearance.
IIRC, Mr. Gasket has the thin .027 head gasket available.
Ive heard horror stories about mr gasket head gaskets leaking. So if i had .040 taken off the heads, i would have to have the intake milled? Thats only .005 or so from stock. Machinest quoted me $80 per head
Professor Fate
Push the button, Max...
I've used the Mr. Gaskets almost exclusively for years, no issues.
Gasket failures are usually the result of improper installation or bad surface prep.
The machinist should be able to tell you how much needs to be taken off the intake or the head at the manifold surface. I'd look it up for you, but I'm tired and I'm going to bed. Take the cut off the heads at the manifold surface. If you take it off the manifold itself, you're married to that manifold. If you ever want to change manifolds in the future, you'll have to have them cut, too. If you cut the head, any stock manifold will still fit.
MOPAROFFICIAL
Oogliboogli
The stock steel gaskets are like .019-.021 thick, the 8553 crushed are about .046-.05 depending on the batch and who measures, mine were. 046... so at say... .045 milled.. -.021... It's the equivalent of having a potential .002-005 thick head gasket ..yielding about 3.5cc or so less than stock chamber volume ....you've only dropped the head down around .022 ...no need to mill the intake side.
Uncle Bob
Shiny paint causes stress.
It's unlikely it was close to the rated CR when it was brand new.
Math will be required.
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