Quick background:

The car is boosted with an ATI d1sc (currently still on stock bottom end). Car is running good at 8psi trapping at about 135mph most likely running about 600RWHP. Heads are ported for boost and have 71cc chambers. I have ARP head studs and the 2002 GM MLS gaskets. The heads have less than 500mi on them.

After the last trip to the track, I noticed quite a bit of steam when the car was first started after it sat and cooled down (it still ran real strong). After some investigation, I identified the head that was most likely having a problem and pulled it. Sure enough one of the cylinders was nice and steam cleaned.

On further inspection, I noticed that the area in which the leak occurred appeared to have a corresponding rough spot on the head sealing surface. There was also some type of scrape/flaw on the outer casting surface. The head gasket actually looked like it was still in pretty good shape to me.

The sealing surface on the head actually feels much rougher in the spot where the leak occurred compared to the rest of the head (one of the pics shows this). I guess that could be a result of the combustion leaking in that direction but I'm not sure.

I took some pics so that you guys could review and give me some advice.

Go to http://photos.yahoo.com/silver2002c5 and click on the folder called "head gasket". The photos are very high res if you download them.

I'm trying to determine if I should just throw on a new gasket or try to get someone to look at the head. I purchased these heads mail order so it would take some time to send them back to the original supplier. To complicate matters, I'm trying to get the car ready so that I can run it in the spring shootout next weekend in San Antonio (I don't plan on winning, just running for fun).

Any advice would be greatly appreciated.

BTW, is there a way to deck the head without impacting compression (just some type of cleanup)?

 

Thats one reason I don't like the MLS gaskets, the surface finish of the head has to have an RMA # of like 60, which is about slick enough to see yourself in it, and not catch a fingernail on anything. I would do what myself, Rob Raymer and many other have done, o-ring it and run a stock GM graphite gasket. Better make sure you get that head resurfaced first though, and make sure they use what is called a PCD cutter to get a smooth surface finish. Or you can send it to us and we'll bust it out.

 

It looks to me like that head has been welded. The reason it looks rough and feels rough is because it is soft in that area and didn't machine well when it was surfaced. The early heads had a U shaped depression in that area which a lot of guys weld up. I think that is what you have but I'm not positive since you didn't mention whether it was an LS1 or LS6 head.

You can have a good shop machine just enough off the head to make it flat. Make certain it is machined as smooth as possible for use with an MLS gasket. Check the block in that area also. They can get an approximate measurement of the depression in the head with a straight edge and feeler gauge or dial indicator. Taking .005" or so off the head will not effect the compression much.

Problem is you may have this problem again because if it is welded and soft it is also weak in that area. Give it a shot and I would suggest you use a Cometic MLS gasket if you do use the head again. Cometic has a spring steel face that will help seal where the stock gasket might not.

Steve Demirjian
Race Engine Development

 

Steve, Rob Raymer at LS1 Motorsports was going through Cometics like underwear until he o-ringed his heads and ran the graphite gaskets. But you are right on with the deck being welded, and how stupid is that, because if they did not weld it you would not have a soft spot and could still run the graphite gaskets just fine. I have never seen anyone weld one of these heads up like that. I think I would go back to the shop that did it and complain.

 

I know Raymer has had good results. But I was running 12-16lbs of boost and my stock MLS GM gaskets sealed fine. I just pulled my heads to have some more work done to them and all the gaskets were sealed fine..all pistons looked uniform. That head looks like it was dropped or smashed on something. Why don't you just have the heads milled .005 as a clean up and then reinstall them. You can use a Cometic (which is MLS) custom to gain back any loss of CC (.006=1cc approx). You don't have to worry as much about quench with forced induction as I understand .045-.050 is fine for a quench when force inducting. I just had my LS6 heads redone to 75cc and am going to use a .064 crushed cometic (my deck height is .014 out of the hole) leaves me with .050 quench area and 9.15:1 CR (-2cc Piston). It looks like you already have a dish in your piston.

I think you would be fine if re-surfaced the heads and bought some new GM MLS Gaskets...did you re-torque the ARP's after a 100 miles...I hear you have to do that too. Good Luck.

 

I thought the same thing. It just seems to coincidental that where you have a leak you also have an indent on the edge like it has been dropped. I think milling them would be the easiest route as well as the cheapest. But you could always have them O-ringed for peace of mind.

 

Looks like it had the U notch welded in and machined to me.....

 

Thanks for all the replies guys.

Sure enough, I just looked again and it is an 853 (97-00) casting and it probably did have the notch and was welded.

I actually called the vendor when I originally got these and said I was a little concerned that the castings were different. He said it made no difference because the cnc program was the same. (It made sense to me, but I did not know about the notch at that time).

Anyway, this particular vendor is a stand up guy so I'm sure he will make it right.

 

When useing the mls gaskets from cometic the serface has to be smooth.The shop you take them to should have a pcbn cutter just for aluminum if they have a broch type they will not be able to get the wright finish on them.I have built Busch Grandnational engines that have come back at over 300 deg water and oil temp and the cometic head gaskets did not show any signs of blowing.If they can get them to work in prostock and winston cup there should be no reason they wont work on these engines.They also make an Hp model for super charged cars and turbos.




mike