Cometic head gasket weeping coolant, should i fix it or do i ignore it.

to determine the bore

 

What would you say is the RWKW power limit for OEM Head Gaskets?

 

Can the OEM Head gasket be used with an 88mm bore?

 

there is no such thing as a power limit on a head gasket. what kills them is hardcore detonation... you could have a 1000hp zed with a stock gasket on a great tune . or a 200hp zed with a pinging tune that will blow the gasket out eventually...

 

Stock head gasket is fine on an 88mm bore, you wouldn't go any larger but. 88mm is the accepted max limit anyway.

Copper is good if you do all the required machining etc, including stainless fire rings.

The gasket is not the issue, lack of clamping force due to only 4 bolts per cylinder is the problem. The toughest gasket money can buy can't fix that issue. Stepping up a size in head studs is the only option there.

Simmo is 100% correct, gaskets dont blow at X power level, they blow due to incorrect machining, assembly or tune.

 

with regards to assembly faults is there any other way to botch up up fitting a cylinder head to a block apart from getting the torque specifics wrong ?

Cheers

 

yes! u can damage the head gasket, you can torque the bolts down in the incorrect order... u can replace the head gasket without machining the heads and/or block. there are many ways

 

Zedzy

why wouldnt you fix it...? its not blown yet its just a leak, but do you wanna wait until it does blow? sounds a bit silly to me mate

 

a head gasket that leaks is BLOWN !!! theres no such thing a intact headgasket that leaks

 

The car runs fine, its only a small weep.
There is no noticeable loss in coolant.


Im sure the cylinders are sealing properly. And the oil and water are seperated (i.e no mixing).

I think i might leave it, changing it out is a real pain in the ass.
I think its just weeping between the 'layers' of the head gasket.

 

http://www.shadydellspeedshop.com/faq.htm

Had a quick read on this, i dont think i will worry about it for now.

Fingers crossed.

 

thats not true, it can leak between teh surfaces without the gasket being blown through,

 

what head bolts/studs are you using??
i know a few people have had sealing issues with the cometic in early days as one of the rivets that hold the mls together was in the wrong spot and once tq'ed prevented it sealing but this has since been resolved.. how long ago did you rebuild it??
was the engine stuffed and forced a rebuild or just somethin you decided to do??

:bash: ill be pissed if mine weeps when i fire it up so much effort i dont wanna pull it down again

 

Cometic's usually leak because the head and deck surfaces aren't machined to the correctly. MLS gaskets require a very different surface finish than traditionally used for composite gaskets.

A surface finish no more than 40ra is needed. If the machine shop doesn't know what gaskets you are using, they have no hope of getting it right, even then, some will still not machine the surfaces to the correct ra.

MLS or Multi Layer Steel gaskets have very little crush and very little surface malleability meaning they do not deform a great deal under the compressive force applied by the head bolts. A surface finish above those specified will not allow the gasket to seal in the grooves left by a surface grinder.

They usually do not leak initially but after a few hot/cold cycles and the head floating off the surface due to cylinder pressure, the head gasket will begin fretting, this then compounds the issue and the leak will keep getting worse.

At the moment weeping coolant is not a big deal, but that will soon lead to chemical erosion of the gasket and mating surfaces as well as the fire ring breaking down because it isn't sealing the combustion gas effectively. Soon enough you will have a proper blown head gasket.

Either way, you need to strip the engine down again and have the surfaces machined correctly, use the correct lube when installing the head studs/bolts and torque to the correct spec. ARP studs use a different torque to factory bolts, and that differs again by what type of lube is used during install.

I also do not suggest going past the Nissan surface machining limits specified in the manual, this can cause issues similar to what you have because the head face is too thin to retain it's shape correctly and can also cause localized overheating in the coolant galleries of the cylinder head.

 

I hate my car.