L98 center intake bolt angle???
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Drifting
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From: rome ny
L98 center intake bolt angle???
i have 91 corvette with L98 aluminum heads. are the center bolts on the intake 90 degree or 72 degree? i am told that just the post 87 steel heads have 72 degree bolts. is this correct
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From: The Top of Utah
Re: L98 center intake bolt angle??? (dtorc4)
I don't know the angles, but the aluminum heads retained the origional SBC iron and aluminum head intake bolt angles, from day one. They did not change in the mid/late 80's when the cast iron heads did. If a manifold will fit a 1960, 1970, or 1980, car, it will fit your 90's aluminum headed engine, bolt angle wise. Good luck, and...
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There is a change for something, but I can never remember the answer to it. It might be the center holes for the TPI runners were changed. Damnit I wish I could remember the answer to this. There is SOMETHING different, I just can't remember what.
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Drifting
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From: rome ny
Re: L98 center intake bolt angle??? (mos90)
from what im was told from trick flow was that the l98 aluminum head was use on the 87-91 corvette. and they retained the same center bolt angle as the steel l98 head 85-86 which was 90 degrees. that would mean my heads would have to same center bolt angle as the pre87 head which is 90 degrees.
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From: Framingham MA
Re: L98 center intake bolt angle??? (CFI-EFI)
When talking about 72 and 90 intake holes, they are talking about the 4 middle intake bolts.
I assumed the 87 up aluminum heads have the 72 degree angle. (I had a set of port 88's but never bother looking becasue I assume they were canted) My 86 with aluminum heads has the 90 degree. If the 87 up C4's have the 90 degree intake, it would make my search for a stock intake that much easier. Can anyone verify this? It is easy to tell if it had the 72 degree intake bolts, the middle two intake bolt would be at different angles (more vertical when bolt on the heads) than the outer bolts.
I assumed the 87 up aluminum heads have the 72 degree angle. (I had a set of port 88's but never bother looking becasue I assume they were canted) My 86 with aluminum heads has the 90 degree. If the 87 up C4's have the 90 degree intake, it would make my search for a stock intake that much easier. Can anyone verify this? It is easy to tell if it had the 72 degree intake bolts, the middle two intake bolt would be at different angles (more vertical when bolt on the heads) than the outer bolts.
Melting Slicks
Joined: Aug 2001
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From: Lockport NY
Re: L98 center intake bolt angle??? (dgoodhue)
This is a quote from the Feb 2002 Hot Rod article on "35 Years of the 350 Chevy"...
"The two center intake-manifold bolt holes on '87-up TPI heads are drilled at a 72-degree angle instead of the usual 90-degree angle. Intake Manifolds must be compatible."
I have the issue, if you're really interested in it...
[Modified by Rich B., 4:46 PM 6/28/2003]
"The two center intake-manifold bolt holes on '87-up TPI heads are drilled at a 72-degree angle instead of the usual 90-degree angle. Intake Manifolds must be compatible."
I have the issue, if you're really interested in it...
[Modified by Rich B., 4:46 PM 6/28/2003]
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From: The Top of Utah
Re: L98 center intake bolt angle??? (dgoodhue)
Re-read my origional post. This is my second "verification". In 1987 Chevrolet revised the cast iron heads in a couple of ways, including the intake manifold center bolt angles. Aluminum heads were phased in on the L98 in 1986. By 1987 all Corvettes got the aluminum heads. The aluminum heads never got the revised manifold bolt angles. All L98 and earlier Corvette heads have the same intake bolt angle. That is 90* to the gasket surface, and "all" as in all 6 bolts per head. Have I left any doubt? Besides what I call personal or possibly common knowledge, the "Chevrolet Power" book backs me up.
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From: Framingham MA
Re: L98 center intake bolt angle??? (CFI-EFI)
A majority of what I read in magazine has mistakes especailly the parts about history and change dates. The intake bolt patern is easy enough to tell if someone has done replaced their intake manifold gasket or if the have done an aftermarket intake and wonder why it is double drilled on the middle four bolts.
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Drifting
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From: rome ny
Re: L98 center intake bolt angle??? (dgoodhue)
ok its offical... my 91 corvette with aluminum head have 90 intake bolts, all of them... all corvettes have 90 center intake bolt 87-91. but if you have camaro or firebird 87-91 and you dont have aluminum heads then your center intake bolts are 72 degree...it is very easy to tell. the 72 degree is almost straight down and are much have a much wider bolt pattern.
Thread Starter
Drifting
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From: rome ny
Re: L98 center intake bolt angle??? (mos90)
the original reason for this question is i am doing a Lt1 intake conversion. but i am buying new heads. when i spoke to Lt1intake.com he sayed it is easier to do the conversion on the 87+ heads. so that is what i am going to buy. but if i have the converion set up for my original heads and use it now then i would have to get the pre 87 head style.
