Hello All,

I am building my f20c for turbo. I've already sleeved the block with 87mm bore and dropped the compression to 9.0 :1 using CP pistons. I plan to stay with OEM head gasket thickness. WHP goals are 400-500 with reliability. I've been looking around for a performance head gasket. Everyone seems to point to Cometic but recently Cosworth has released their gasket too. Company wise, i believe Cosworth is 10 times better the Cometic, because they build race engines for a living. The Cosworth design seems to also perform better on paper.

Problem: Cosworth only makes a 88mm bore head gasket and cometic only makes a 89mm bore. Please correct me if i'm wrong. I like the Cosworth but there is a 1mm difference between my bore size(which is OEM size) and the 88 mm Cosworth head gasket. Is this normal for the head gasket to be slightly larger like this?

I've already emailed cosworth but it might take forever until them answer.

A little help here please. Someone has got to know this


thanks

 

OEM.

 

 

Inline

 

OEM, thats the only way to roll

 

OEM

 

To me over the past 6 months I have seen a few post of cars blowing motors pushing the OEM. It seems to make the most power but leave less room for error. However, the 3mm seem to only last so long.

 

OEM here.

 

Hh? He's not talking about thickness. He is talking about bore size. And his motor is built for lower compression.


To the OP:
use an oem hg with NEW I repeat NEW oem head bolts or arp head studs. With a straight head and block and proper torque sequence, you will NOT have a problem with the HG sealing for as much boost that you could possibly throw at it. Unless the tune is off causing high cylinder pressure, then there may be a problem....

 

Thanks everyone for your inputs so far. But can someone tell me why/how the gasket fails. The most common cause of a failed head gasket is?

Cosworth replies:

"Yes, 1mm larger bore leaves .5mm space around the bore which is perfectly acceptable. Most OEM gaskets are about 1mm larger then the cylinder bore to compensate for over boring."

i am really leaning towards the Cosworth gasket. This car is going to see a lot heavy track time. I am using ARP head bolts by the way. ACL race bearings all round too.