need to know 
Cylinder Head Milling???
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Cylinder Head Milling???
I have the GM 113's on my 88 L98. These heads have 58cc combustion chambers. The stock set up is 9:1 compression. Can enough material be milled of to get say 9:5 compression, with out having to mill the intake manifold to match? I know if to much is removed, the intake doesn't line up... Thanks... 
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
You might want to double check your specs. I am not aware of any of the aluminum headed L98s with a 9.0:1 compression ratio. I believe your 1988 already has 9.5:1 compression.
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Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Originally Posted by CFI-EFI
You might want to double check your specs. I am not aware of any of the aluminum headed L98s with a 9.0:1 compression ratio. I believe your 1988 already has 9.5:1 compression.
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Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Most machine shops have charts that tell them when, and how much, material to remove from the intake gasket surface of the heads to match the amount removed from the deck surface, for a proper fit. They also, usually have charts to tell them how much of a cut it takes to remove a given number of ccs. A little quick math will tell you how many ccs your combustion chambers will have to be reduced to go from a 9.5:1 compression ratio to 10.0:1.
You are better off to have the intake side of the head milled rather than milling the manifold itself. If you mill them both, you create a "matched pair" that won't work well, individually, apart from one another if you want to separate them later in a swap. You would have to mill a new manifold to match the old if you wanted to make a change and you old manifold would have very limited appeal to others. And if you take off enough, don't forget the bottom of the manifold.
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You are better off to have the intake side of the head milled rather than milling the manifold itself. If you mill them both, you create a "matched pair" that won't work well, individually, apart from one another if you want to separate them later in a swap. You would have to mill a new manifold to match the old if you wanted to make a change and you old manifold would have very limited appeal to others. And if you take off enough, don't forget the bottom of the manifold.
RACE ON!!!
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Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
I'm soaking it all in gang, I appreciate your replies, I tally all this info up, and it helps me alot, as 99% of the time. It turns out right on... 
Gotta love this gallery. I try to give as much as I recieve, and it makes me feel part of an elite group. As there is a mechanic here in town. That thinks he needs $100.00 to answere a few questions. I know people have to make a living, but this guy worships the green God a little to much I think. Since joining the forum, I haven't had to talk to him once... 
Gotta love this gallery. I try to give as much as I recieve, and it makes me feel part of an elite group. As there is a mechanic here in town. That thinks he needs $100.00 to answere a few questions. I know people have to make a living, but this guy worships the green God a little to much I think. Since joining the forum, I haven't had to talk to him once...
Melting Slicks
Joined: Feb 2006
Posts: 2,753
Likes: 15
From: backwoods upstate ny
thin head gaskets from your friendly chevy dealer--p/n 10105117...they come one to a package, make sure they order a pair...cheaper than napa...just like milling the head, gotta run premium fuel.
thickness is .o28'', cost if you buy em as ''%^&*#'s moonlight garage" should be abt $35...these are recommended by gm perf prod for cast iron/ aluminum heads....if you get some other brand,be sure they are compatible with alum heads and won't brinell (chew out) the heads
thickness is .o28'', cost if you buy em as ''%^&*#'s moonlight garage" should be abt $35...these are recommended by gm perf prod for cast iron/ aluminum heads....if you get some other brand,be sure they are compatible with alum heads and won't brinell (chew out) the heads
Last edited by redrose; Jun 4, 2006 at 10:18 AM.
Racer
Joined: Aug 2002
Posts: 386
Likes: 0
From: Lancaster Lancashire
Try the Mr Gasket 0.028" gaskets (MRG-1134 about $40/pair from summit) They are better than the stock 0.051" thick gaskets and should give you a full 1/2 point of compression. I would resist the tempation to skim the heads any significant amount, they are not too thick compared to after market ones. If you want to improve things further, take the engine out and have the deck skimmed 0.015". With the above gaskets, this will take you to around 10-10.6:1 depending on piston valve reliefs, but you will probably run into severe detonation with the stock L98 cam and this set up. Stepping up to a Tpis ZZ9, Accell '219' or a GM Hot cam should work OK with it though. Obviously a larger inlet would really be needed to benefit from this as well. Then you may as well have the heads ported a bit............ It depends how far you want to go and how much you want to spend. The important thing to remember is the engine is a package, think things out carefully.
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Originally Posted by Davemc1963-87conv
Try the Mr Gasket 0.028" gaskets (MRG-1134 about $40/pair from summit) They are better than the stock 0.051" thick gaskets and should give you a full 1/2 point of compression. I would resist the tempation to skim the heads any significant amount, they are not too thick compared to after market ones. If you want to improve things further, take the engine out and have the deck skimmed 0.015". With the above gaskets, this will take you to around 10-10.6:1 depending on piston valve reliefs, but you will probably run into severe detonation with the stock L98 cam and this set up. Stepping up to a Tpis ZZ9, Accell '219' or a GM Hot cam should work OK with it though. Obviously a larger inlet would really be needed to benefit from this as well. Then you may as well have the heads ported a bit............ It depends how far you want to go and how much you want to spend. The important thing to remember is the engine is a package, think things out carefully.
Originally Posted by redrose
thin head gaskets from your friendly chevy dealer--p/n 10105117...they come one to a package, make sure they order a pair...cheaper than napa...just like milling the head, gotta run premium fuel.
thickness is .o28'', cost if you buy em as ''%^&*#'s moonlight garage" should be abt $35...these are recommended by gm perf prod for cast iron/ aluminum heads....if you get some other brand,be sure they are compatible with alum heads and won't brinell (chew out) the heads
thickness is .o28'', cost if you buy em as ''%^&*#'s moonlight garage" should be abt $35...these are recommended by gm perf prod for cast iron/ aluminum heads....if you get some other brand,be sure they are compatible with alum heads and won't brinell (chew out) the heads
Originally Posted by tequilaboy
I think cometic has an .027 head gasket that should be worth about 2ccs.
Originally Posted by CFI-EFI
Most machine shops have charts that tell them when, and how much, material to remove from the intake gasket surface of the heads to match the amount removed from the deck surface, for a proper fit. They also, usually have charts to tell them how much of a cut it takes to remove a given number of ccs. A little quick math will tell you how many ccs your combustion chambers will have to be reduced to go from a 9.5:1 compression ratio to 10.0:1.
You are better off to have the intake side of the head milled rather than milling the manifold itself. If you mill them both, you create a "matched pair" that won't work well, individually, apart from one another if you want to separate them later in a swap. You would have to mill a new manifold to match the old if you wanted to make a change and you old manifold would have very limited appeal to others. And if you take off enough, don't forget the bottom of the manifold.
RACE ON!!!
You are better off to have the intake side of the head milled rather than milling the manifold itself. If you mill them both, you create a "matched pair" that won't work well, individually, apart from one another if you want to separate them later in a swap. You would have to mill a new manifold to match the old if you wanted to make a change and you old manifold would have very limited appeal to others. And if you take off enough, don't forget the bottom of the manifold.
RACE ON!!!
Originally Posted by 88BlackZ-51
stock is 9.5. thinner gasket?
Thread Starter
Burning Brakes
Joined: May 2006
Posts: 1,097
Likes: 2
From: Richfield Utah
Originally Posted by CFI-EFI
Before you spend your hard earned, make sure what you order/buy is for a Gen I engine. I'm not sure everything mentioned, above, is.
RACE ON!!!
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