RaleighSS

Long story short .... leak down test has showed I have some intake valves leaking causing a drop in peak HP ... this is like my second time this has happened... I honestly never remember any mechanical over-rev not do i bump the limiter often if at all.... Running a stock cast LS6 head ported by TSP and a stock bottom end ... Valve Springs are new Com Cam double versions.... Cam Card I have on file is as below

Gross Valve Lift .612 .612
Duration @ .006 277 280
Duration @ .50 228 230
Lobe separation 113

RX-Ben

What pistons are you running?

RaleighSS

stock bottom end

RX-Ben

Did you fly-cut/notch the pistons?

geerookie

IMHO I'd look into the lifters. At upper rpm's the stock ones tend to pump up and with that high of lift your valves will hit the pistons.

rustyguns

most the stuff i have read is to run under .600 aftermarket lift on a stock engine. i am not an expert though

rustyguns

any head work... aftermarket head gaskets ?