HP limitations on OEM rb25 head gasket

[chad b.]

Before someone takes a swing at me, I already searched, but couldn't find any good solid info. Not opinion, but experience, what are the limitations of a stock OEM rb25 head gasket? I had a Cometic on my old motor, but without a decked block, I'm wondering if the stock HG with a set of ARP's would be just as good. My HP goal is no more than 550whp pump+water/meth. A friend of mine has made 600+whp on a stock HG and head bolts, but he is also the luckiest bastard on the planet with motors, so I can't go by that alone lol.

[Carl H]

stock head gasket with arps bolts will hold quite a bit.
unless you're pushing loads of pressure and power you'll be ok.

500 wheel is very doable with a stock hg.

[240z4u]

550 wheel with studs/stock gasket should be absolutely no problem at all. I am in the high 400s at the wheels right now and plan on going further, I haven't even considered going to a metal gasket. I did ARP studs years back when I had to pull the head to remove busted exhaust studs, it's been a very durable combo that has held up to even my horrible tuning work.

[chad b.]

Well thanks fellas! For the price of a Cometic, you can almost buy a complete engine gasket kit from Nissan. That'll save me a little cheese.

[Carl H]

cometic's are a waste of money on these motors...jdm brands are the best bet for MHG.
if you're interested might be able to source an apex gasket for a decent price...pm me.

[RRRRB]

i have had great results with Cometic on my RB. I've used 2 never had ANY issues with either of them.. (just swapped heads)

I also have one on my 600whp Honda never any issues with that one either.. why don't you care for them Carl?

i actually have a new Cometic gasket Chad its an .051 gasket i will sell it for cheaper than you can find it, anywhere online.

[outlaw7]

^well from what ive read on other forums, mhg in general but especially cometic actually increase possibility for gasket failure unless both the head and the block are machined to be perfectly straight where as the oem hg will have a bit of forgiveness


I've also seen a couple threads where people are pushing over 900 hp with stock gaskets, cant remember where though

[Carl H]

just seen too many leaks from them, unless the block and head finish is just right they inevitably leak.

i think they work out ok on hondas because they are designed to be used with a mlshg from the factory.

[RRRRB]

Yes me and a friend found his cylinder head finish (RA) was to ruff for MLS gaskets, thats what was causing the issue with his car... however he was on an oem honda gasket.. i will continue to use Cometic as ive had great luck with them, i dont see what the difference would be between Cometic and any of the Japanese brands..

On the other hand i have always went thru and retorqed my head gaskets on the RB and the H22a, Ive done this after about 1k miles RB was a little loose but VERY little..
The honda on the other hand needed it...

Heres another story of mine, a few years ago, i decieded to install some valve springs on my honda, (with the head on the car) well obviously i had to remove the cams etc, i had never retorqued the head gasket.. The engine had about 15k miles on it since i had built it.

I decieded to put a torque wrench on the bolts to check them, i got about 3/4 turn out of them!! i couldnt beleive it. never had any issues with over heating or anything but i can only assume that was coming if i didnt catch that.. I continuesly RAPE that car on 28psi+ and 8500 rpm on pump and meth

[Carl H]

its always good practice to recheck head stud torque when using arp studs after a couple hundred miles of use...they do stretch some but once they have you're good to go for quite a while.

i've always retorqued motors i've put studs just to check and normally get 1/4-1/2 turn out of them.

[meet07]

I spoke with my local machine shop about using the cometic gasket. I told him about the rumors I heard online about the cometic leaking and he told me is based off the RA. He proceded to tell me that they had 2 machines. If I where to get the cometic he would have shaved my head/block with the machine that cuts alot smoother. I just got the cosworth gasket. Used it twice then relaced the 3rd time b/c it failed