Just a quick question, I heard from a guy about some new high pro heads that GM was developing and they are supposed to be a pretty good buy. Some sort of L87 head or something, I don't know jack when it comes to casting numbers. So does GM have anything new out? Or am I barking up the wrong tree?

 

L92 or L76

 

Correct, the L92 heads complete are just under $400 and they flow extremely well. The downside is that they will not work on a bore size smaller then a 4.00". So LS1/6 owners will either have to get a 6.0L block or resleeve their existing to a 4.00" bore to use these heads.

 

There's an article on them in the new GM Hi-Tech Magazine. It's the one with the flat black 99 Z28(In SS trim/z06 wheels) that they swappen an LS7 into. Great mag.

 

out of the box they flowed 332cfm on the intake side...don't remember the exhaust. I thought they said u could use the L92 heads on a LS1/6 block but u had to use a LS2 head gasket...maybe I read it wrong (english class wasn't my strongest subject). $1000 fully assembled, nice. u do have to switch to the L76 intake because of the intake runners are designed after the C5R heads (runners sit higher) BUT the L76 intake WITH TB, injectors AND fuel rail for the AMAZING price of $500...how it's so freakin cheap I dunno, it's composite too. they also have a carb style intake for the L92 heads. U also have to get new headers I believe because like the intake runners the exhaust runners sit higher.

oh, and about the LS7 in the F-Body...not impressed with the times they squeezed out of it. It has to run faster than a 12.00@115...has to.

 

In a vette you do not need new headers when running L92 heads.

 

again the vette guys have the advantage

 

Why is that? Wouldn't the exhaust ports on stock LS1s and LS6s be the same regardless of which car it is in? There is going to be a change regardless.

 

Well. That 12.00 at 115 also left the driver unable to pull the transmission out of 4th gear thus requiring them to tow it home. They mentioned they wanted to do as little modification as possible. Hence why they left the almost trashed stock T56 in there. He mentions how with a better tranny a mid 11 would be possible.

 

I don't see why the F-body guys shold have it any differently. The guy on the corvetteforum who is running his 402 w/ the L92 heads and L76 manifold is using standard corvette American Racing 1 7/8ths long tubes w/o modifications.

 

is this true? the part about being able to use L92 heads on a ls1 as long as you use an ls2 head gasket.

 

well I hope someone on here looks thru thier GMHP mag and sees if I'm right or not...I don't have my mag in front of me, it's at work.

 

No, it is not true. Your MOTOR needs to have a 4.00" or even better 4.030" bore.

Ben T.

 

dont worry-we get the 'vette tax' on everything we buy

 

The only way I think you might get the L92 heads to work with a stock ls1 bore is to use a smaller intake valve in the head, and that means using new valves and a new valve job, which means adding to the cost to the point of buying stock ls6 heads with a mild port and valve job.

One day if my block gets trashed, I'll got to a bigger bore and top it off with a set of these heads and intake. Till then, I'll make due with 430hp and ls1 heads.

 

Man you guys are awesome thanks for all the research and information! Does anyone know the intake valve size on the L92 heads? Are they 2.08" or 2.10"?

Quote: The Alchemist
"The only way I think you might get the L92 heads to work with a stock ls1 bore is to use a smaller intake valve in the head, and that means using new valves and a new valve job, which means adding to the cost to the point of buying stock ls6 heads with a mild port and valve job."


If you can use a set of AFR Mongoose 225's with 2.08" intake valves /1.60" exhaust valves on an LS1 why can't you use the L92's (if equipped 2.08" intakes)? Is it that the bridge space between the valves on the L92's is greater than it is on the AFR Mongoose heads? What kind of clearence issues come with the L92's when compared to the AFR Mongoose heads? Thanks again in advance this time!

 

The 260cc (or however huge it is) port is going to be a lot for a 346ci motor. I think a ported LS6 head would be a better option for a small cube LS1. It would have plenty enough CFM potential.

Ben T.

 

L92 valves:
GM #12590771 2.16 intake valve
GM #12582719 1.59 exhaust valve

 

Yeah well that about clears that up

I see your point Studytime cost effectiveness and risk management! Just didn't know the specs!

 

Do you guys see these heads being welded up (like patriots LS6 "style") to work on stock bore LS1s?

Was anyone else's GMHTP mag missing pages? Mine had extra pages and was missing some. I didn't get the entire story on the new heads and intake.