L98 Head Gasket
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
L98 Head Gasket
I finally got my heads pulled from the engine. I was talking with a friend and he suggested I use Felpro 1003 gaskets instead of the Felpro 7733 PT-9. Is the 1003 gasket better to use? Thanks for any help or suggestions. Thanks.
Max G’s
Joined: Nov 2008
Posts: 2,751
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From: Monroe OH
NCM Sinkhole Donor
If you're running stock engine, I'd go with stock GM head gaskets. If you are looking to increase your compression ratio a bit, go with the thinner head gaskets, but make sure you get a high quality head gasket or you will be pulling the heads again. Do not, what ever you do, get the cheap Fel Pro's from the parts chain stores. There are different grades of Fel Pro's.
Race Director
Joined: Apr 2002
Posts: 10,036
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From: Anaheim CA
My machine shop (Superior Automotive in Anaheim, CA) recommended the FelPro 1094. It's like the 1003 but it has a rubberized coating on it. They use them on all the Chevy small blocks they build and claim they have never had a leak.
The 1003 and 1094 are .015" thick and the 7733 is .039" thick. You'll lose a lot of compression with the 7733.
The 1003 and 1094 are .015" thick and the 7733 is .039" thick. You'll lose a lot of compression with the 7733.
Advanced
Joined: Aug 2010
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From: Kaneohe Hi
First thing I would do is get a solid measurement on how far the piston is in the hole when it is at top dead center, and ftom that use a gasket with a compressed thickness that gives you a quench of 0.035-0.045. You put on that 0.015 shim head gasket on a zero decked block the pistons will kiss the heads, likely you will be .025 in the hole but measure to be sure as too much quench will cause knock
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
The engine is stock. I was reading some other articles in the forum & I see others talking about the bore size being too big on the 1003 gasket, is the 1094 the same bore as the 1003? I definitely want to go better than stock so that I'm not having to do this again within 15k miles. What other better suggestion are there for the correct gasket?
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
The engine is stock. I was reading some other articles in the forum & I see others talking about the bore size being too big on the 1003 gasket, is the 1094 the same bore as the 1003? I definitely want to go better than stock so that I'm not having to do this again within 15k miles. What other better suggestion are there for the correct gasket?
I couldn't find anywhere where you stated what year L98 you have; but given the cylinder head replacement gasket set you mentioned (7733PT9) is for 1986-1991 L98's, I'm guessing you have aluminum heads. If so, go with the Fel-Pro 1010 gasket. If you have cast iron, the Fel-Pro 1003 is the best choice. Both of these gaskets are better than the OEM orange leakers. (Replaced the OEM gaskets on both '89s with 1010's years ago and still no problems.)
Drifting
Joined: May 2002
Posts: 1,581
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From: The Motor City
If the heads are aluminum and the block is iron, don't use Felpro 7733 gaskets. They are the WRONG gaskets! They are fine for iron/iron, not good for aluminum/iron. It took me a long time and a lot of research to find that out, and I am amazed Felpro still lists those gaskets as the replacements for L98 engines.
I went with Felpro 1010 gaskets when I replaced them on my L98 ('89 Corvette) almost 10 years ago and I've haven't had an issue since.
I went with Felpro 1010 gaskets when I replaced them on my L98 ('89 Corvette) almost 10 years ago and I've haven't had an issue since.
Thread Starter
Instructor
Joined: May 2011
Posts: 213
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From: Miramar Florida
My car is an '84 but the engine was swapped from the Crossfire to an L98 from an '86 (aluminum heads).
With the Felpro 1010 gasket, is it the same thickness as stock? If I did use the 1003 gaskets (they were given to me-Free), is there advantages or disadvantages with the added compression?
With the Felpro 1010 gasket, is it the same thickness as stock? If I did use the 1003 gaskets (they were given to me-Free), is there advantages or disadvantages with the added compression?
Last edited by Bredd1; Jul 6, 2011 at 05:51 PM.
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Drifting
Joined: May 2002
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From: The Motor City
Some L98s from '86 were iron head/iron block; If I'm not mistaken only the convertibles were aluminum head/iron block. If you can, take the valve cover off one cylinder head and post the casting number. It'll be easier to determine if it's an iron or aluminum head.
As for the gasket thickness, I don't know what the stock head gasket thickness was. But chances are, even if the 1010s are a bit thicker than stock, the difference in compression won't be anything you will feel as far as the vehicle's performance. If you're really concerned about it, install a set of 1.6 roller rocker arms when you reinstall the cylinder head. The gains there will more than make up for any loss in compression you might see from a slightly thicker head gasket.
As for the gasket thickness, I don't know what the stock head gasket thickness was. But chances are, even if the 1010s are a bit thicker than stock, the difference in compression won't be anything you will feel as far as the vehicle's performance. If you're really concerned about it, install a set of 1.6 roller rocker arms when you reinstall the cylinder head. The gains there will more than make up for any loss in compression you might see from a slightly thicker head gasket.
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
Using 1003 gaskets on an iron block w/aluminum heads is not a good idea. The 1003 gaskets use a pre-flattened steel wire to seal each bore while the 1010 gaskets use a pre-flattened copper wire. The 1003 gaskets can indent (brindle) your aluminum heads while the 1010 won't.
Hope this helps!
Le Mans Master
Joined: Jul 2007
Posts: 5,356
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From: No HOA, New Hampshire
Cruise-In X Veteran
St. Jude Donor '09
No, clean the gasket surface with a "lapping"? stone and check with a straight-edge. Any gaps, then to the machine shop.
Race Director
Joined: Sep 2003
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From: Database Error Indiana
Ive used the 7733s several time with no issues. They work fine with alluminum heads. Just decide how much thickness you need. A wire ring gasket can leave its imprint in your alluminum head. Its called brinnelling, I think.
Team Owner
Joined: Oct 2004
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From: altered state
St. Jude Donor '05
spend the 60 bux or whatever they charge to run it real quick on their machine. 
Melting Slicks
Joined: Nov 2008
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Some engine builders I have spoken to in person like a quench area as tight as .010" or less with a heart shaped or kidney shaped combustion chamber.
They claimed gains between 10 to 30 hp peak at the flywheel on a Superflow waterbrake engine dyno.
No detonation takes place.
+/ positive engine deck engine builds.
Piston protrudes above the deck surface at TDC with a Fel- Pro race style head gasket.
The Fel- pro race series or BBC marine series headgaskets are best I think.
What I have used for many years even on the street.
BR
They claimed gains between 10 to 30 hp peak at the flywheel on a Superflow waterbrake engine dyno.
No detonation takes place.
+/ positive engine deck engine builds.
Piston protrudes above the deck surface at TDC with a Fel- Pro race style head gasket.
The Fel- pro race series or BBC marine series headgaskets are best I think.
What I have used for many years even on the street.
BR
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Some L98s from '86 were iron head/iron block; If I'm not mistaken only the convertibles were aluminum head/iron block. If you can, take the valve cover off one cylinder head and post the casting number. It'll be easier to determine if it's an iron or aluminum head.
Last edited by 86PACER; Jul 17, 2011 at 03:17 PM.
