I realize this should be in gen IV but I figured I might get more input here since the heads are from gen III. I have a stock LY6 motor (9.6CR vs LQ4's 9.4 CR) & I want to know if its poss. to mill the 243s down enough to raise the compression conciderbly while still having reasonable P2V clearance? (.630 lift)

thanks,

 

I think it would a bad move. The LY6 heads are LS3 heads with large rectangular ports. A much better flowing head.

Also you will see if many other post, DURATION and not so much lift is the problem with PTV.

 

unsure if ly6's came with L92 heads factory but if the pistons have valve reliefs i believe you could mill quite a bt but if they are flat top then you'd have a certain stopping point.. what camshaft are you wanting to run for starters? my friend has a ls1, 232/236 cam with 243's milled .020 and it clears fine.

 

I'm 99% certain all the LY6 option engines have Ls3 heads.

 

LY6 comes OEM with 823 casting heads. they have the solid stem L92 intake valves, and inconnel exhaust valves.
I believe it is a mistake to swap them for the 243's, but thats your call.
As far as milling them down for compression, yes you can cut them SUBSTANTIALLY, but you will most likely need to flycut for PtoV clearance. I believe that it is worth the hassle to flycut, in order to be able to cut enough to get compression where you want it.
Barrett

 

Thanks for the input guys.

 

Leave the ls3/l92 head on there. Cam it and make 500hp

 

Add the ls3/l76 manifold too.