Cometic Vs. OEM Headgasket
 

Which would you choose and why?

i vote oem because a friend of mine just blew his cometic.

yeah ive heard every now and then some issues with cometic.. but i wonder what world racing or ptuning use on theirs, im thinking oem

OEM... its the only thing i use and recommend. the oem is very thick and durable actually and can hold 400 easy... Id worry more about using upgraded headstuds more then the actual head gasket. the gasket is usually one of the last things that fail on this motor

any cometic users wanna chime in? would like to get opinions from both sides of the spectrum... what seems to be the issue with the cometic hg? bad design? crappy material? just curious

THIS.

Cometic fails.

I'm leaning towards OEM being the better choice.

OEM for sure! I just got done replacing my Cometic for the OEM. I talked to Rod at World and they use OEM as well.

that 1... # 2 the oem is multi layer - cometic is 3 solid peices 2 metal and one cooper
oem is 3 peice. but the middle peice has compression rings around the cylinder to seal it vs the solid piece

Higher boost applications the OEM just cant hold up. But for anyone that is running about 25psi or less, OEM is the way to go. More than that, The cometic holds up well.

Sorry haven't post for a while.

We use the factory-style OEM gasket. Both the oem gasket and cometic gasket for the 2az-fe motor are MLS gaskets, ie. they are comprised of 3 layers of steel, with a viton coating on the two outer layers. They are similiar in design in terms of material, thickness, and number of layers. But what makes the oem gasket more suited for forced induction application is the design of the middle layer.

The middle layer of the oem gasket does not span the entire area of the deck like the top and bottom two layers. The middle layer only covers the thickness of the deck area surrounding the combustion chamber, sort of like a fire ring. The thickness of the middle layer is about 2 thou in thickness so essentially when the head is bolted down onto the block, it creates a tigher seal around the bore's deck surface. What this does is creates something similiar to a "step-deck" block, where the cylinder bore's deck surface is machined a few thou higher than the rest of the block's deck surface.

MrC

we run 50psi+ using a OEM gasket...wouldnt run anything but!

Wonder why 2 OEM gaskets failed at 25ish psi. However the Cometic is holding up fine after much higher boost and Abuse? Input from the shops?

Could be many reasons. Need for details on build, components used and exactly what happen that might have lead to gasket failure.

MrC

My guess would be it was installed wrong or high spot in the block.

thanks for the great info guys. much appreciated

does the fact that im going .5 overbore mean anything in the difference between the two gaskets?

bump

no problem going .5mm over with oem gasket.

MrC

usually when a head gasket fails its caused by something other than the head gasket