chpmnsws6

iTrader: (70)

So I bought these valves:
https://ls1tech.com/forums/lsx-parts...parts-pic.html

I took them to Capitol City Machine Shop (The only trusted Machine Shop in Springfield IL) Friday. Today I received a call being informed that the valve margin was .025, where minimum is .050. He said that because of the narrow valve margin from being cut too much, I stand a high chance of burning a valve if installed.

I just wanted to verify what the minimum spec for the valve margin can be. The machine shop said the Valves are not usable, and that I would be wise to order a new set for them.

Any insight?

99RTA

iTrader: (-1)

Don't use um....PLUS the fact its a reputable machine you trust. why would they lie? The valves need a certain thickness to keep the valve from overheating. The margin is too thin heat will build up and ruin the valve. Purdy simple.

studderin

iTrader: (28)

theres nothing wrong with what they feel works for them.
But you will find alot of guys doing fine with thouse valves, and margin size. And some guys know how to make great power with thouse valves, and a vavle job on that head.

HCCH

Which valves are in question? Intake or Exhaust? For an exhaust that would be way too thin. For an Intake with lighter seat pressure you could probably get away with running the margin at .025" for awhile without having head tuliping. From GM the intake margins are fairly thin. .030"-.035" on most I've measured.

chpmnsws6

iTrader: (70)

The intake valves are the ones in question. This will be a higher compression N/A engine with an ASA cam (ported 241 heads milled .040)

It has LS6 springs and Ti retainers.

HCCH

Your best bet would be to get some valves that have not been ground and replace the ones you have. Although the ones you have should run with no issues, the longevity will not be as good as ones with a thicker margin.

PREDATOR-Z

PM, Joseph or Eric (SAM) and ask them if those are stock measurements. On same note there has been issues with stock LS6 valves from overheating, issue is usualy exhaust.

Nitroused383

iTrader: (10)

My stock 853 heads with 110k miles on them had a very thin valve margin but were sealing fine (.025) or so. The set of LS2 243 heads I bought only had 14k miles on them and the margin was around .030" from the factory. Old school small block chevy stuff uses thicker margins but GM made these valves with pretty thin margins. These same questions went through my head but I redid them anyways and have had no issues yet with 10,000 miles on the setup.

chpmnsws6

iTrader: (70)

I also found the "missing margin"

The LS6 intake valves are .6mm longer then LS1 valves. That equates to .023" which means these are cut .002 more then my LS1 valves which were WELL within spec (800 mile old valves)

Case closed!