What are your hp/tq increase?

Thanks.

 

If its a stock 6L you are going to have bad valve shrouding, low speed driveability problems, and possibly spark plug fouling problems. Those heads are HUGE for a 6L in a heavy truck.

 

That is merely speculation of course. GM seems to think they will work fine on an engine with only 10 more ci than a 6.0. The difference of .060" on the bore is only .030 per side with is about the thickness of 7-8 sheets of paper. I would not call that bad valve shrouding if someone was to ask me.

If there was any loss of low speed tq most people wouldn't notice it since they would have a higher stall and the low speed losses would mostly be off idle.

This is coming from a person that used a set of 205cc heads on an engine that he was worried about low rpm tq.
It was 418 ci, ~11:1 comp, 237/242 duration cam I think, and a 3400 stall.


I am running L92's and a carb style intake on my 370ci set-up so we will know then. If I ever have time to put it together.

 

i have a set of L92s for the 408

 

Going by what many of the "reputable" engine builders on tech have said and you know as well as I do that when I ordered all that **** for my 418 that I didnt know very much at all about this kind of stuff and was "misguided" by the speed shop that I was dealing with. Get your POS running then lets see what tune you are singing.

 

Im interested in hearing results Ive been eyeing those heads and intake for myself

 

The new vortec max motor (L76) is a 6.0L and has the same heads as the L92 so looks like they should work on a Gen III 6.0L, you need the L92/L76 intake, though the GenIII won't work.