exSSer

Still mulling over my build setup. If I use Cometic .040 gaskets, my SCR will be 11.53, and DCR will be 8.96. If I retain the stock MLS GM @.060, my SCR will be 10.95, and DCR 8.52, which I think is safer for use with 92 octane pump gas. Will a Quench of .052 lead to added detonation?

Brian Tooley Racing

iTrader: (13)

The GM gasket should be .054" minus the .008" the piston is out of the hole, should yeild around .046", which I think is great.

One other thing to remember, detonation is all about cylinder pressure, the better the head flows, the more cylinder pressure it makes and the faster you get into detonation.

Patrick G

iTrader: (14)

Your DCR is not 8.96:1. We already decided that 2 weeks ago. If you're still talking about the Crane cam on the 112LSA with no advance, your DCR is in the low to mid 8s. You're either using the wrong numbers at .006" or you're using the wrong calculator.

exSSer

Well, I found out the cam is +5 advance built in, and the dur.@ .006 is 281. So the numbers I listed above were what came out in the calcs. And Brian, when I used search, all the posts indicate the '02+ GM MLS gasket compresses to .060. But please correct me if I'm wrong in any of these assumptions. Thanks, Dave.

DavidNJ

I think there are two issues here: quench and compression. You should be adjusting chamber size and valve pockets to get the right compression, not quench.

slowride

iTrader: (3)

I had the same question about the GM MLS gasket so I just mic'd my old one and get around .053"-.055" of compressed thickness on the fire ring. It's not the .060" many people claim.

JakeFusion

iTrader: (7)

Exactly. But since I imagine the cam and heads have already been purchased, you can do a couple of things. First, buy an adjustable timing set and retard the cam 2-3 degrees to lower the DCR when running the Cometic. 5 degrees of advance is going to kill any power past peak ~6300. That sounds like a shitty cam, imo. Also, I assume 61cc chambers on the heads?

If the cam spec's out at .050" around 230, then your VEs are good with 2 degrees of advance. If you retard the cam to a 110 ICL and use the .040" Cometics, it comes out to SCR of 11.53:1 and DCR of 8.73.1. That works on 93 octane. The alternative is to install on a 109 ICL and run a .045" Cometic, but the DCR is still 8.69:1, which I think is too high for a quench area of .037". DCR of 8.73:1 and a quench of .032" is going to work much better. The strong DCR is going to make plenty of torque, so even if the IVC is off a few degrees as originally hoped, the cam will become more intake biased and will hold the powerband longer and still make about the same torque numbers, because the VEs will be near optimal for the intake manifolds available.

exSSer

Thanks for all your guidence. I may rethink the cam. When I ordered it they told me it was 0* advance, but the cam card that came with it says differently. What about the same setup using the TQ'r V3? 111 LSA and 0* advance? IMO, it's better to spend a little $$ now and get it right the first time.


And hypothetically, if I stick with the original cam,and use the stock GM gaskets, would that be OK with tuning and 92 oct?

JakeFusion

iTrader: (7)

It wouldn't be perfect with the GM gaskets. If you don't have an adjustable timing set, they are only $115 or so (Rollmaster LS1, JP LS2). This is a good investment anyway, as you can degree whichever cam you get. You'll have to shim the oil pump, but eh.

GuitsBoy

iTrader: (4)

Thats really good news! I feel a lot better about these gaskets now. I was gonna suggest the 6.0L gaskets as they are around that thickness, and even though the bore is larger it would more than make up the difference if the 5.7L gaskets really were .060. Thanks for measuring the gasket though. I already threw out two used pairs and forgot to measure both times.

exSSer

I wouldn't be too quick to celebrate, because everywhere that sells the '02-newer gaskets insist they're .060 compressed. This may not apply to the ones they make for earlier model years.

GuitsBoy

iTrader: (4)

Ones for earlier years were graphite, and were .052 - .054 thickness. The MLS were introduced in 2002, or possibly late 2001. The 6.0L truck MLS gaskets are .054, so i never understood why they would make the 5.7L gaskets .060. I know everyone that sells those gaskets advertises them as .060, but everyone who actually uses and measures these usually says theyre thinner. I wish I had remembered to mic up my gaskets before chucking them out. Can anyone else verify the MLS thickness with a micrometer?

slowride

iTrader: (3)

Trever at Texas Speed even agreed with my .053"-.055" reading. If I set the mic to .060" it just pulls right off the ring with no friction. I can get a lower reading then .054" if I really clamp down on it, but that seems excessive. If you measure off the fire ring where no sealant is used it is around .052".

DavidNJ

What I don't understand is why you would use such a large quench with an aluminum block engine. .040-.045 are conservative iron block setting. .028-.030 has been used in more radical, 7k max rpm iron blocks.

Aluminum blocks can use less. Tony Mamo has suggested .033-.038. Others have run down to .025. Just get it warm before revving it!

World uses .060 in their crate engines. But that is a very conservative setting in case a customer really, seriously over revs it.

Why are people using the radical setups on this forum using these relatively large quench dimensions?