Head Gasket Question
#1
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Join Date: Jul 2013
Location: Great Southern Taxland...
Posts: 369
Head Gasket Question
I have a '73 J head 455, standard and unmolested.
I'm pulling the heads off to replace with C heads and have a Felpro rebuild gasket set. I believe the head gaskets are .042".
I can get a set of Cometic head gaskets that are .027"
What head gasket thickness did the factory use?
What would the difference in compression be between the two? Would the cometic gaskets be worth half a compression point, ie 8.5:1 to 9.0:1?
I'm pulling the heads off to replace with C heads and have a Felpro rebuild gasket set. I believe the head gaskets are .042".
I can get a set of Cometic head gaskets that are .027"
What head gasket thickness did the factory use?
What would the difference in compression be between the two? Would the cometic gaskets be worth half a compression point, ie 8.5:1 to 9.0:1?
#2
I have a '73 J head 455, standard and unmolested.
I'm pulling the heads off to replace with C heads and have a Felpro rebuild gasket set. I believe the head gaskets are .042".
I can get a set of Cometic head gaskets that are .027"
What head gasket thickness did the factory use?
What would the difference in compression be between the two? Would the cometic gaskets be worth half a compression point, ie 8.5:1 to 9.0:1?
I'm pulling the heads off to replace with C heads and have a Felpro rebuild gasket set. I believe the head gaskets are .042".
I can get a set of Cometic head gaskets that are .027"
What head gasket thickness did the factory use?
What would the difference in compression be between the two? Would the cometic gaskets be worth half a compression point, ie 8.5:1 to 9.0:1?
Edit: I should clarify. The stock Olds steel shim head gasket has a compressed thickness of about 0.017". Either gasket is thicker than that. The 0.042" gasket will LOSE about a quarter point of CR.
#3
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Thread Starter
Join Date: Jul 2013
Location: Great Southern Taxland...
Posts: 369
Okay thanks Joe.
Looks like I've some simple math to do to pick pistons that will get me to around 9.5:1 with the Felpro head gaskets and around .004" off the heads. I'm guessing 9.75-10.0:1 dish or thereabouts will suffice.
I don't intend to cc the heads, it's not that important. Just want to improve on the crap '73 factory compression.
On a similar note, are the Felpro .042" head gaskets going to upset the lifter/ pushrod/ rocker arm clearances, or should the hydraulic lifters take up the slack?
Looks like I've some simple math to do to pick pistons that will get me to around 9.5:1 with the Felpro head gaskets and around .004" off the heads. I'm guessing 9.75-10.0:1 dish or thereabouts will suffice.
I don't intend to cc the heads, it's not that important. Just want to improve on the crap '73 factory compression.
On a similar note, are the Felpro .042" head gaskets going to upset the lifter/ pushrod/ rocker arm clearances, or should the hydraulic lifters take up the slack?
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jensenracing77
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August 11th, 2015 06:49 PM