I'm sorry I asked this on the 2L forum; here seems like a more appropriate place...
I plan on running 22PSI+ (on race gas of course) on my JDM Type RA motor and I was wondering if there would be any added margin of safety in going to Cometic head gaskets instead of the stock ones. I believe both are 3 layer stainless steel...

The Cometic units are made out of better steel and have customizeable thicknesses. Both are about the same price so a lot of people just go with the Cometic units when they're doing the rebuild.

-Geoff

Stock, period.

I think it a waste of money to use anything other than the stockers, unless you've changed the comp height on the pistons, or need to adjust quench.

S.

I use stock on standard-bore engines. I just copper-coat them. I only use Cometic if the bore is larger than stock.

Absubtle
PA

Stock OEM gaskets are what we use. The different thickness of the Cometic gasket throws off your cam timing, compression ratio and squish area.
Each of these changes have a negative effect on producing power :)

Quirt Crawford
www.crawfordperformance.com

Stock gasket is very good and preserves the squish area to OEM spec which may or may not be important in your application.

Stock OEM gaskets are what we use. The different thickness of the Cometic gasket throws off your cam timing, compression ratio and squish area.
Each of these changes have a negative effect on producing power :)

Quirt Crawford
www.crawfordperformance.com
However, going with a thinner gasket would improve squish IIRC. My understanding is that you want the smallest possible squish, which maintaining enough clearance for rod stretch at high RPM.

However, going with a thinner gasket would improve squish IIRC. My understanding is that you want the smallest possible squish, which maintaining enough clearance for rod stretch at high RPM.

I would'nt imagine "rod stretch" to be a large factor in our engines (as with AL rods). I would be more concerned about piston rock and valve float. I put >.030" in my engine I recently sold, due to the p-w clearances.

S.

However, going with a thinner gasket would improve squish IIRC. My understanding is that you want the smallest possible squish, which maintaining enough clearance for rod stretch at high RPM.

You are correct... However, decreasing your squish area is like flirting with your girlfriends sister :eek:



Quirt Crawford
www.crawfordperformance.com

You are correct... However, decreasing your squish area is like flirting with your girlfriends sister :eek:



Quirt Crawford
www.crawfordperformance.com
Chuckle. :lol: Quirt, it's not that bad. Honda guys have been doing it for years, and at 9500 RPMs, the rod stretch can get ugly. It does need some TLC though to get it right. Some of the best engine builders I know have good track records with this.

Chuckle. :lol: Quirt, it's not that bad. Honda guys have been doing it for years, and at 9500 RPMs, the rod stretch can get ugly. It does need some TLC though to get it right. Some of the best engine builders I know have good track records with this.


Don't get me wrong, a tight squish is very benifical :)

Quirt Crawford

I've run up to 35 psi with the stock head gasket and a little 70 shot of N20 and the stock head gasket has never let me down. "If it ain't broke, don't fix it!"

Phil
www.elementtuning.com

Phil, Quirt, You guys have me convinced. Stock it is! Saves me money too :D Thanks a lot for the information!

Phil, Quirt, You guys have me convinced. Stock it is! Saves me money too :D Thanks a lot for the information!

You are quite welcome :)

Quirt Crawford

unless you want to increase or decrease compression? I don't think you can do that with a stock head gasket. If i was running 19psi, I would try to decrease the compression. And I don't know if the stocker is copper, but the cometic is.

And if you want to save money, buy the cometic, not the stocker, because you have a better chance of replacing the stocker again.

unless you want to increase or decrease compression? I don't think you can do that with a stock head gasket. If i was running 19psi, I would try to decrease the compression. And I don't know if the stocker is copper, but the cometic is.

And if you want to save money, buy the cometic, not the stocker, because you have a better chance of replacing the stocker again.

Using a thicker head gasket is a crutch and by no means the optimal way to decrease compression. Quench is very important as it provides the necessary turbulence to increase combustion efficiency. The EJ motors have very poor efficiency and this is why we have to run so much ignition timing to get a decent burn. By increasing the quench you loose the extra bit of turbulence that helps speed up the burn. I’ll take the higher compression any day and tune around it rather than going with the thicker head gasket. In most cases using the stock head gasket still keeps the engines under 9:1.

I also beg to differ that “there is a better chance of replacing the stock..” head gasket compared to a Cometic. They are cheaper but not better based on my experience.

Thanks,
Phil
http://www.elementtuning.com

Here is a video of our 2.8L R4 motor while running a set of stock head gaskets :)

Enjoy! http://www.crawfordperformance.com/gallery/video/the_rivalry_part_1.wmv

Quirt Crawford
Crawford Performance

I use stock on standard-bore engines. I just copper-coat them. I only use Cometic if the bore is larger than stock.

Absubtle
PA

What do you think of the copper-coating, Quirt?

Would you use it?

Thx, S.

Is the copper coating simply a spray on like Permatex?

What do you think of the copper-coating, Quirt?

Would you use it?

Thx, S.


I have used it half a dozen times, Steve. Although I'm not sure if it helps. :)


Quirt