Metal Headgasket Comparo Vs O-ringing?

[Shockster0429]

Currently I am building a 2.7 liter stroker out of my rb25. Using JE 87mm pistons, eagle rods, rb26 crank so on... I've had quite a few issues with my 25 over the last year, long story short, I want to place my motor together, stick it back in the car and not have to touch it for a long long time.

This is what leads to me making this thread, I've done a good deal of searching on here for people who have o-ringed their block and haven't found much of anything. Any body doing it? are you placing a groove in the head, and block? What hg gasket are you using when doing it? Who feels this is nessarcy as compared to using a MHG. I'm looking into the Cosworth MHG if I don't o-ring, anyone have any issues with their MHG? ARP head studs will be in place as well.

I plan to eventually run 30 + psi, with race gas through my 35r t4, maybe even upgrade down the road to something slightly larger, so I'd like to have ZERO HG leaks assuming its properly tuned and so forth...

thanks for any insight.

-Cory

[R31Nismoid]

This thread is a good start, bit of past info in it.

http://www.skylinesaustralia.com/forums/Me...et-t127280.html

[Shockster0429]

This thread is a good start, bit of past info in it.

http://www.skylinesaustralia.com/forums/Me...et-t127280.html

Thank you, However I did find that earlier. I was looking more for information regarding the standard head gasket, o-ringed block, and ARP studs vs just standard HG, ARP studs vs MHG besides Cometic... I just don't trust their product from what I've seen and heard.

[datsqik]

I wouldnt use a oring with a standard h/g as the standard type head gaskets have a limited life span with all that extra heat any detonation just destroys them. To use an oring with a standard h/g you need to keep the oring in close where the fire ring is which can cause the top of the block to close in which means the block should be honed with a torque plate and dummy head gasket and oring in place. You can use a copper h/g with an oring and keep the oring out a bit further so less chance of the top of the block closing in but i would still recommend torque plate honing be used. With a cast iron block and ally head I fit the oring in the head and a receiver groove in the block as the oring forces the copper h/g into the receiver groove and as cast iron is stronger than ally i prefer it that way to stop the sharp edges of the receiver groove rolling over as it can do in ally. I get a 39 thou wide groove machined 25-30 thou deep into the head and use 40thou wire so that it protrude 10-15thou once its pushed into place. 10thou is enough if done without using a receiver groove and up to 15thou if a receiver groove is used. The receiver groove in the block should be 40-60thou wide and around 20thou deep to allow the cooper h/g to be pushed into the groove. These grooves need to line up perfectly for it to work properly. Best to have a torque plate made that lines up perfectly with the bores that uses dowell locating holes that go all the way thru so you can reverse this onto the head so the machine shop has something to setup from. Ridgecrest make a few different thicknesses of cooper head gaskets that are cheap enough but you must use a good sealant like silver sealant to seal up around the fluid holes.

As far as metal h/g's go I reckon the power enterprise ones as they have like a double grommet that gives lower clamping pressure on the inner lip and higher pressure on the outer grommet so less chance of the bores closing in at the top.

http://www.powerenterpriseusa.net/products...ket/gasket.html

Ive also had good success with the hks stopper and the tomei grommet h/g's.

If your using a 25 block then it would be advisable to drill and tap the block to suit the arp gtr studs.

[The Mafia]

f**k that was a good answer. Well done mate.

[Shockster0429]

Datsqik thank you for the detailed response on the o-ringing, it sounds like it would be a better option for me to just stick with a MHG. I see the sizes that Power Enterprise listed for the rb25, they only have a 1.5mm HG.. I was looking for a 1-1.2mm max to keep the compression ratio up since I will be at 8.5 to 1 with my setup as it is, for this is a street car/ weekend racer.

Re tapping my block for 26 studs, I'd most likely have to drill out my head as well? Also the head gasket holes, from what I remember they were rather tight on my ARP studs when installing the stocker?

Heres a write up on the Cosworth MHG done by one of our major American GT-R experts any opinions on the matter?

http://jdm-insider.com/Blogs/Eric/?p=386

[datsqik]

Ive never done the 12mm stud conversion on a 25 block with a 25 head only the 30 block with a 26 head which is pretty straight forward and only requires that the holes at the top of the block need to be relieved slightly before tapping so that the tap starts with the existing thread and not from the top of the block. Ive done some 1/2" head studs into a sr20 which requires the block be drilled and taped as well as larger locating dowels be used which means the head/block needs to be drilled to suit but the head holes clear the studs.

I havent had anything to do with the cosworth headgaskets but I'd imagine they must work fine if xs engineering use them.

That gtr of theres would have to be one of the best setup time attack cars around.

[Shockster0429]

Datsqik, I think I'll just keep the standard 25 ARP studs, its not like I'm shooting for 1000rwhp+ here. I I just don't want any coolant or oil leaks when boost is added, and it seems as if people have had good success with other MHG's besides Cometics.... so I'll give XS a call Monday and possibly end up running the Cosworth. I appreciate the help, any on going discussion of the topic please go ahead, its good information.

Yes the XS GT-R is a monster, Speed actually had a series called "street tuner challenge" Where 3 teams pick a car and build it. Its competition was a golf, and I think a saturn ion.. lol. No contest.