I'm thinking that the present lift also exceeded the recommended max for the stainless valves that were originally installed in the heads. Original build sheet listed lifts as .5XX, which is where they would have been with 1.7 rockers. The difference turned out to be exactly the difference between a 1.7 and the 1.8 (LS7 style) rockers that were used.

So what would be the ideal characteristics of a head for this application?

 

i have the cathedral mast heads and my cam is split as well since the exhaust port is ls7 based...something to think about

 

fyi my intake is 2.25 and its stainless, my exhaust is inconel and i posted my lift with 1.8s

 

That's a big valve. I was looking at various heads and one of them did not recommend stainless with over something like .613 lift. Could have been PRC, but not certain. What springs/spring pressures with those?

 

they said 700 lift springs, i told them my cam specs and they set the heads up for me

it is a big valve on a big head, they are the 295cc mast heads

curious if you had simialr heads what was your pushrod lenght? mine are 8" with my tie bar lifters

 

Hmmm..... original invoice says "LS1 push rods Comp Cams." Build sheet said "Smith Bros 5/16" x 8.075"
Current build sheet says TFS-21408050 (8.050") Pretty sure what I just pulled out was the Trick Flows. Non tie bar Morel hydraulic rollers.

 

that makes some sense, my lifters require only .030 preload and my block was decked

8" long
3/8" thick
.134 wall thickness

wonder if your setup was flexing those pushrods, said anything over 7.5 ya should have 3/8 if you have the clearance especially with that valve train

 

Are you running stock rockers? The problem tends to be in the way the rockers pull at the valves over certain lift. The LS7 style rockers done have the same problem until much higher lift numbers.

George that exactly my point on the cam. It's not the split specifically i don't like, it's that the exhaust open is far too late for these heads. Especially at his boost level.

 

Thinking that if I was comparing heads, I should be looking for better exhaust flow.

I'm running Crower SS shaft mount rollers

 

I see their spring options include ".700 lift" and "turbo" Not that they ever have any LS7 style heads available.

Seems that many feel that my spring pressures were too low for 20 PSI/7000 RPM...currently at 155/450