Hi,
I have a 91 L98 with stock iron heads.
I just picked up a set of used 98 truc vortec heads. The truck heads have 64cc chambers and I was wondering what the stock chamber size was for the L98. Also...what is the stock compressed head gasket thickness?
thanks
wj

 

Should be 64 cc, too.

 

If you don't mind me asking, how much did the used Vortecs run?

Did you get from private party or "used auto parts"/ salvage yard?

 

I believe the "stock" head gasket on a iron headed L98 is the typical steel shim factory gasket. Which is .015" thick.
The bore size is 4.10" compressed volume is 3.5cc.

If you just replace it with a typical felpro composite gasket
.039 to .041 thick the cr will be lower.

typically the cc of these gaskets is 8.9 to 9.1cc
The gasket bore size is 4.166 typicaly.

If you want the same or higher compression using a thicker .039" gasket you have to deck the block or shave the head or a combination of.

You want a total compression quench spec of .040" ideally including the gasket. anything beyond .060" aand no quench effect.

details detail details....
Don;t assume the head is axactly 64cc's cause it says so somewhere. they do vary some. from the factoryn and are often reworked. "
measure twice cut once"

 

Got a casting number on the heads?

Only way to know 100% is to get out the syringe and cc the head.

 

thanks, everyone!

whoaru99: I bought them used from an individual. They have 25K miles on them…from a 98 truck…paid 220 for heads, rockers,p-rods,bolts,valve covers.

F-Bird’88: I actually want to lower the compression a touch. This engine is goin in my 88 chev PU truck…running a single turbo and using an old Air Sensors DECU to control fuel events.

84z28350: I was hoping that the heads were 58ccs so that I could knock a point off of the compression…it is a tough balancing act to try to lower compression so that I can run more advance or boost and still not screw up the quench so much that it detonates no matter what.

I guess I knew I would need to yank the heads to know for sure but have been considering installing this engine, as is and then later on this winter swapping the heads. If the engine is at 9.0:1 or so right now I can probably get away with it but if it is pushing 9.8 then that is a no go.

Does anyone know if there are either adapter plates or different base manifolds that adapt the stock tpi to vortec heads?
thanks
wj

 

Yeah,

Edelbrock has a TPI > Vortec base, so does TPIS (made by Edelbrock from what I've read on this forum), and then there is one available from Scoggin-Dickey Chevrolet.

There may be others, but these are the ones I know about.


EDIT: On second thought, that TPIS intake may NOT be for Vortec heads - not certain there....