I am purchasing some stage 2 heads that have been milled 0.030. This, by my calculations, makes the compression ratio around 11 - 11.1 with a 60-61cc combustion chamber.

Is it recommended to install metal head gaskets instead of the stock graphite gaskets when going to a higher compression ratio? Where is the best place to pick up a set of these gaskets? Are they thicker than the graphite gaskets? Are the stock head bolts strong enough or should I go ahead and purchase ARP studs?

 

The stock mls are actually pretty good although, you could go with the high-end Cometics. They are available from various vendors such as ThunderRacing.com in .045, .054, .078 and other thicknesses at the stock bore or oversized. I had a leak with Cometics and my 5.3 L heads due to a very slight mis-match of the perimeter land on the gasket and the edge of the casting. I ended up, unfortunately, having to go with the pre-'01 composite gaskets to ensure that I got a good seal. If you're going with LS1/6 heads, the Cometics or the stock mls will work well. Another thing about the 5.3 L heads to watch for is the notch in the base surface which can allow coolant to leak due to a lack of seal pressure at that point. The notch is located on the outer edge between #5 and #7 or #6 and #8 cylinder depending on the bank.

As far as head studs, I personally highly recommend the ARP 6-pt. stud set. Awesome especially if you have to pull your heads again. There are several benefits to running studs vs. bolts.

Btw, love the sig pic.

 

Hey Patches, thanks for the compliment. That's one clean engine you posted a pic of. I really want to go with the studs this time, when I put my cam in I had one of the stock bolts break and it was a nightmare getting it out.

My question is still this about the gaskets though... is it necessary to switch from the graphite gasket when going to a milled head? If I do use one of the gaskets you've mentioned will this enlarge my combustion chamber?

Thanks again for the compliment, I always look for technical posts by you... you always seem to be right on the money.

 

Is the stock bore 3.905 and the stock gasket thickness 0.0524?

 

Those dimensions are correct. The choice to go with graphite or mls depends on your motor and application. The graphite gasket is required for earlier LS1 blocks where the decks were not milled as flat/smooth as the 2002+. They are a more forgiving gasket. The mls are hearty and can easily withstand higher compression ratios and the application of N2O and FI. I'm having no trouble with my higher compression and would have no issues applying N2O if I saw fit.

If you go to a thicker gasket, you'll lose a bit of compression. I believe the rule of thumb is a point (.1) of CR to every .006" of gasket thickness. Remember that you always need to take ptv clearance into account first before choosing your gasket thickness.

 

It looks like the deck will be my problem then... I've got a 99. Is there any way to correct this issue, or at least check to see if it is actually an issue with my block?

I have considered ptv clearance. In looking at the 0.045 thickness gasket, this gasket will not compress like the graphite gasket correct?

 

It will compress slightly but not nearly as much as a graphite gasket. FYI, a lot of pre-'02 guys have gone with mls with no problem. My bud's '99 block looked as flat and smooth as mine. No way to know for sure except to measure it but I believe they can handle the mls gaskets based on what the fbody guys have been doing for so long.

 

My experience with this: I have a 99 FRC. I just installed a set of AFR 205's milled .010" mounted on Cometic .040" thickness gaskets. My pistons were out of the hole about ~.004". I had a spot on my deck on the drivers side in the front where it looked like the guys that put the motor together dropped the corner of the head on it. There were 4 radiused dents starting from the middle of the front of the deck to about 3/4 of the way down. The dents got smaller and shallower as they got lower. I was prety upset. I cleaned the deck really well. Then I got some FastSteel and put it in the dents and made it really smooth and flat. I mic'ed it afterwards and it was within .001". So I decided to go with the MLS gaskets. I've had them on for about 1 month now and have beaten on the car and put about 500 miles on it so far. No issues. I wouldn't have put the Cometics on if I didn't get the deck flat and fill those dents though. BTW, they were on the other side of the coolant holes but one of them went into one and you could see where coolant was pooling in the dent up to about 1/2" out into the gasket where it got too shallow to go any further.

 

My block is definatly not in that shape, judgeing from when I did my cam swap. I will evaluate the situation again when I pull the heads this next time but if memory serves me I belive my block is very smooth.

Thanks again for the replies, if anyone else has any suggestions I'm all ears!

 

Here is some more info to confuse you!

http://ls1tech.com/forums/showthread.php?t=111207