RB25 with Thinner MLS Headgasket (0.76mm)

[mynameisdaniel]

RB25 with Thinner MLS Headgasket (0.76mm)

I've done a lot of searching but haven't found anyone who has tried this before (possibly for a good reason?).

My R33 is a track car and I'm rebuilding my RB25DET after cracking a piston ringland, I was running E17 but will be going E85 for the extra safety that offers. For the time being I will be continuing to use standard pistons (with a hone and new rings).

I'm considering ARP head studs as I'm getting sick of buying single use OEM bolts (this is the third time the head has come off now) and I'm looking at a MLS head gasket for the same reason.

My calculations seem to indicate that going from the stock head gasket (1.1mm compressed) to a 30 thou head gasket (0.76mm) will raise my compression ration to 9.3 which would be a nice bump with E85 use (standard turbo, with plans to go highflow later on).

Has anyone attempted this before (or shaved the block for the same effect)? My main concern is the effects this will have on the quench area, I'm using standard cams so valve clearance should be okay.

[Ad's]

This idea is swimming around in the back of my head that I am considering, because I'm still running the standard headgasket at 326 kw on 22psi and I would like to change the head gasket and swap over to ARP studs.  

Will be following this thread.

[33GTRV]

Piston to valve clearances.

[KiwiRS4T]

If you are often pulling the head off consider getting a Tomei metal HG which can be re-used.

[Ke55pig]

Intersting idea

[Guilt-Toy]

a guy i know has used the same cometic head gasket over 4 different motors.

[doo doo]

measure your piston deck height, you might find the rb25 pistons have positive deck height. Yes your main concern will be your quench height which shouldn't be less than .75mm. Even with that height you might find you get a bit of noise after carbon build up on top of the piston, but that takes a while too. 

[Dale FZ1]

He's running E85.  Carbon buildup won't happen.

[mynameisdaniel]

Thanks guys - looks like I'll have to do some careful measuring as no one seems to have info on factory clearances... I will also be allowing room for rod stretch. As Dale said, carbon build up won't be an issue with E85 or the amount of use it gets.