02RedHawk

iTrader: (17)

Need some clarification on the compressed-thicknesses of various GM-OEM LSx 5.7L head gaskets. Its pretty clear what's available from FelPro, Mr Gasket, or Cometic, but concerning OEM-GM gasket compressed-thicknesses, I'm now confused as hell.


- What is the stock head gasket used on 2002 5.7 LS1s? Graphite or MLS?
- What is the stock head gasket used on all 5.7 LS6 motors?
- What year did GM start using the MLS gaskets on LS1 motors?
- What is the COMPRESSED thickness of the MLS gasket?
- What is the COMPRESSED thickness of the graphite gasket?


There's so much conflicting information in various past threads (many intensive searches), including in our "sticky" above on the Compression-Ratios - for every posting or thread I see stating one thickness, I see another with different info.

PaceParts lists the MLS compressed gasket thickness at .060". Most other threads list the MLS compressed at .054" or .052". And even in our sticky above, there are individual postings that state the MLS has a compressed thickness of .060", .054" and .052". Can't be all three....


Hope to get some definitive clarification on this....! THANK-YOU!

DrkPhx

iTrader: (15)

The MLS gasket should have a compressed thickness of .052. The older graphite gasket should be .040 compressed. The graphite gasket was used from 97-98, then GM switched to the MLS from then on (and still uses them for the LS2).

PREDATOR-Z

Are you 100% sure about that??

02RedHawk

iTrader: (17)

That's now yet another varying bit of info from Drk Phx. Never heard that the graphites were .040" compressed.

See why I'm so confused?

ArcticZ28

iTrader: (14)

I had graphite gaskets on mine and it's a 99.

PREDATOR-Z

I've had a 99 and a 00 and both had graphite.

DrkPhx

iTrader: (15)

Must be 2000 and up with the MLS.

02RedHawk - I apologize for any confusion. Honestly, I would call a sponsor for the actual compressed thickness of the graphite gasket. I do know it is less than the MLS.

1fastWS6

iTrader: (3)

Nope....

.060" for the MLS
.053" for the graphite

100% sure of that. Have measured them myself.

Graphite was used on 97-01, all LS1's AFAIK. My '01 had graphite. Believe the MLS came out in '02 model years on LS1's.

02RedHawk

iTrader: (17)

Thank-you 1fastWS6.

So, kinda taking this thread now to more of a heads-question, provided that we're all in agreement that the gasket-thicknesses are correct (MLS is .060", Graphite is .053").

Would it be recommended to take .010" off my set of LS6 heads -and- use a .045" Cometic gasket (net reduction of .025"), instead of just milling .025" from the heads and using the stock .060" MLS gasket? (that is, I should then have my quench a bit more optimal, and likely produce more power at the same CR?)

Cam is a 224/224 .581" 114+2, heads and cam going on an '02 Firehawk. No PtV issues with either of my two options above; just looking for which would be "better" - thinner gasket + slight milling, or more milling and stock gasket.

smask04C5

iTrader: (1)

slight mill with thinner gasket will provide better quench. if pistons are .008 out, quench will be near .037 on cometic .045 gasket. good

bigdsz

iTrader: (1)

Graphite gaskets are absolutely, positively .053" compressed.

1fastWS6

iTrader: (3)

ditto that

bigdsz

iTrader: (1)

Milling increases the CR but has no effect on the quench. Thinner head gaskets increases the CR and betters the quench.

smask04C5

iTrader: (1)

point taken bigdsz, I should have said that it is more beneficial to mill head a little and go with thinner gasket, rather than milling head more and thicker gasket. quench is determined by gasket thickness, not chamber volume.