Are there any head gaskets that are .040-.045 that will work without surface prep? IMO the stock gaskets leave too much gap when you're trying to work with higher compression and 93 octane. Autozone offers a Mr. Gasket head gasket at .042 at a 4.000 bore, anyone had any experience with those? At $28 a side they're a good deal, might not be the best for boost but maybe for heads/cam?

 

I have .040" Commetic MLS head gaskets and they hold perfect, I used ARP hardware on them. The engine was built by a shop, they took the steps to meet that 50 ra surface standard for the gaskets.

 

^ that's what we used on my buddy's MS4 + PRC S1 Head swap.. I like them better then the metal ones, IMO.

 

Leave too much gap for what?

 

Quench. .035-.045 recommended, w/ closer to .035 considered better. I figure a 64 cc chamber and a .042 gasket is better than a 59 cc chamber and a .058 gasket (which is what the GM MLS replacement gasket is sold as).

I'm just putting together a parts list for heads/cam. Trying to get both quench and DCR in range for some patriot heads and an xe-r cam. Judging by past successes by other people, ~8.5 DCR should be a good bet assuming proper engine tuning and cooling.

 

Quench is the distance from the top of the piston to the quench pad on the head (the flat part) so the size of the chamber is irrelevant to quench.
Why is the stock quench bad? Or are you running shorter pistons?

 

Use the GM gaskets and you won't have a problem.

I'm running 11.8:1 on 93 and making 530rwhp through a 2.5" Magnaflow with 450rwtq coming in at around 3500 on the GM gaskets.

 

Also, when I did my heads/cam combo on my other car to make 471rwhp, I used the GM gaskets as well.

There's no need to aggravate yourself using other gaskets and having potential leaking issues.

 

Understood, but it still affects compression ratio. In other words, thin gasket + big chamber = thick gasket + small chamber (or close enough on my numbers).

Now that a few people have chimed in I'm considering a thin gasket + small chamber. It seems that up to almost 12:1 compression isn't bad as long as you've got the right cam and cooling system to support it. 93 octane and some octane booster always help, too.

Anyway, it's not that the stock LS1 quench is bad, it just seems (to me) that there's room for improvement. Given how easy it is to change this clearance and improve detonation tolerance doing this I don't see why I wouldn't want to change it up (provided it doesn't leak ). I'm not running over .600 lift so I don't see PTV clearance being an issue.

Unless anyone has a reason LS1s like more quench? I was always told the lower the better, within operational limits. BTW Kraest what was your DCR for those combos?

 

Another thing you want to think about is that Patriot welds their 045 heads to get the chamber size down from around 72cc to 58cc or whatever you specify.

Other heads are shipped out at 62-64cc and if you want to make the chambers smaller, you mill them.

Something to think about when talking about quench and PtV clearance...

 

Yes at this point I'm most likely going with Patriot heads. I assume PTV clearance won't be an issue with ~.010 less quench and a .600" lift cam, will it? From all I've heard most people don't have problems until ~.630". Right now I'm leaning towards a Comp XE-R grind (232/234, 281/283, .595/.598 112 LSA 110 IVC). With a 59cc chamber and .042 gasket it should put me at about 8.9 dcr if I install it straight up. Do you think that's too high or will I make it? Using octane booster won't bother me, I don't put that many miles on it. I just don't want to have to pull timing back because I pushed it too far...

Does anyone know what lift Comp rates their advertised duration at? I understand the XE-R has quite aggressive lobes but most other brand cams are around 300 advertised duration that are low 230s .050 duration.

 

Since you're only installing it 2 degrees advanced AND staying below .600, you won't have ANY problems at all with PTV clearance. PTV clearance comes into play when you're going over .640 lift on a 4 degree advanced cam with alot of duration.

The Futral Motorsports F-13 and F-14 High Lift, TR T-rak Cam, and TR T-Rex are all over 230 duration and .640 lift and 3-4 degrees advanced that all work on stock height heads with no problems.

I believe that I pretty much had the least amount of PTV clearance you'd want on a motor (around .065" ? ) with my old heads/cam setup. It was a Dart 225cc head that was milled .020" with the 236/239 .600/.611 Futral Motorsports F-15, but it was only advanced 2 degrees.

You'll be very safe as long as you don't mill the heads or use a real thin head gasket. I used the stock GM gasket.

Pretty sure that Comp uses .006 lift for advertised duration.. Crane uses something weird like .004.... At 49* difference between ADV and .050", your cam looks pretty damned aggressive

 

LOL I know, but it seems to be the hot thing for LS1s now, slam it open, slam it shut... I guess it makes sense if you can control it.

What about compression? It seems really high but I'm not used to the longer duration setups.

 

Like I said before.... I'd keep the stock head gasket. The stocker and those heads should net you around 11.2-11.4:1. Plenty enough for a heads/cam combo with decent duration. Remember the stock pistons come slightly out of the hole. No need in going with a thinner gasket that WILL cause you un-needed PTV clearance problems..

To reiterate what I said before:
My .020" milled 58-59cc heads with a STOCK gasket and 2* advanced cam with 236 degrees intake had minimal PTV clearance at .600" lift. By MINIMAL clearance, I mean that with a manual over-rev like making a 3-2 shift or something of that nature, I would have bent the valves at the least and/or caused massive internal damage. You WILL need to be careful. The only suggestion I can give you if you're set on using a thinner than stock gasket is to make sure to check the PTV clearance before you crank it up or to flycut the pistons.... also, note that I was using a 2.055 intake valve on those heads... if you're using a 2.02 or something smaller, you should be alright....My current PP heads use a 2.02 and make 530 rear-wheel.