I'll be installing ET 245 heads as soon as they can get them to me. My question is about head gaskets. I've viewed some threads on this and other forums that indicate that people are having problems with the Cometic head gaskets. Any thoughts on the best sealing head gasket would be appreciated. The engine is N\A with a compression ratio of about 11.5:1. Thanks in advance.

 

Not sure what the chamber size is on your heads, but on my Darts I am going with the GM 6.0 MLS gasket. I have read the Cometics don't like anything that is out of plane more than 0.001 and with a motor with 20K miles, I just don't want to risk them. Not sure how forgiving the GM gasket is, but it is thicker so it must be more forgiving than the Cometic as far as surface matching. I have scratched the Cometics off of my list as I also don't want to get the car back together only to have a leak.

 

I have researched a lot about the cometics .040 gaskets because I also had the same concerns. What I found is that Block and head surface MUST be prepped very well to ensure a proper seal. Hundreds and hundreds have used these gaskets and have 0 issues and are completely satisfied and then there are a few that have not had good luck at all. I formed the opinion that the ones that failed had not installed them properly or had not properly prepared the mating surfaces. Cometic and felpro are two very reputable companies that have been in buisness for a long time, have spent big $$ in R&D, and produce quality products.

Now I had a hard time letting go of $140 for gaskets, but bought a set the other day because with the high compression i plan to run I wanted my engine set-up properly with everything perfect including the squench(sp?). Every shop I talked to recommended the cometics ( I needed a .040 gasket in my case). I will be installing them tonight or tomorrow as per the cometic directions and expect them to seal properly with no issues. The first time I built my motor I used the stock MLS gasket because I also read a post about a cometic leaking but looking back now I regret not using them along with not "optimizing" my set-up the first time. Looking at the gaskets and knowing I've prepared my block and heads (most time consuming task for a heads/cam job IMO) I am confident that they will seal properly and my "Squench" will be were it should. BTW I expect to have ~11.2:1 comp ratio FWIW -Wayne

 

Hell, I cracked the ringland, before the gasket even thought of giving me any problems

 

Squish.

 

Are you using an iron or alum block?....... Cometic is used for the dissimilar metal qualities of an iron to alum. head for sure.......ask the builders you know and see what they say
I have them on my 97 for that reason
Also..........I have read more than a few folks reusing Cometics 4 times

 

Haha Thanks Cajundude your right!

I copied this from Madbill on ls1tech:

"I realize most of us use the words "squish" and "quench" interchangeably, which is not unreasonable, since they describe the same close-clearance region of the combustion chamber. However, apart from confusing anyone new to the concept, there is a subtle assumption baked into these word choices, which I think is misleading: "Squish" tacitly indicates that the operative phenomenon is the ejection of a high speed, turbulence-inducing gas jet from between the head surface and the fast and closely approaching piston, thus increasing turbulence = improved flame speed = reducing spark advance requirements = less negative work on the piston's upstroke and reduced time for detonation to raise its ugly head.
"Quench" on the other hand seems to suggest directly damping out detonation by sucking heat out of the mixture in this sensitive region via a combination of large, relatively cold, metal surfaces and perhaps some turbulence to increase the heat transfer.
My money's on "squish" as the more accurate description."

 

Did you check your block/head squareness, or was this a matter of cleaning real well? I don't have a problem cleaning the heads and block, but it was the recommendations on squareness that got me away from Cometic.

 

No luck with them on my car. Ended up using fool-proof graphites.

My $.02

 

I've had the .040" Cometics on my car since I did my AFR 205 and cam about a year ago. I also removed the heads and had them milled again for more compression, then I used the cometics to notch my pistons. I had the heads on and off about 50 times although I didn't put a full torque on them, just snugged the cylinder being notched. However after all this I reused the ones I have on and have had no issues up to this point, about another 2k miles. They worked well for me. I didn't use any copper spray either, although some do. Tony Mamo recommended them to me and I use an aluminum block and aluminum AFR's.
One more empirical observation I have made is, most of the guys that have had failures have used ARP bolts or studs, I'm using GM head bolts.

 

Cometics here too. Jeff Creech insisted on the stock head bolts.

 

Cometics .045 here!!

 

One more empirical observation I have made is, most of the guys that have had failures have used ARP bolts or studs, I'm using GM head bolts.[/QUOTE]

Interesting. ECS told me to get the ARP studs and the GM gaskets. I wonder if the problem with the Cometic could have the issues with the studs

 

7 sets of them and even reused them up to 3 head removals. No issues.

 

I used Cometics, ARP bolts, new AFR 205's, I did the install, super cleaned the block deck. I have had no issues, leaks etc. I wonder why some fail ?

 

Cometic .045 here with stock LS6 heads, and ARP head bolts. Did the h/c swap myself Running two years, 16k miles, no issues. I did take alot of time to prep the block, just hand cleaning, nothing heroic. Well over 100 runs at the strip on this setup. One reason I dont do new heads is that they might not seal as well as these did, heh... I did not use the copper spray on these, if I reused I probably would.

Not an expert, just my $.02... Good Luck!

 

There is a pretty good explanation of anything related to this topic in a tech article I wrote here ==> http://forums.corvetteforum.com/show...19&forum_id=48 I was more focused on Gen I engines but the idea is the same.