Jump to content
SAU Community

RB25 with Thinner MLS Headgasket (0.76mm)

mynameisdaniel
 Share

Recommended Posts

mynameisdaniel Contributor

mynameisdaniel

Posted
Posted
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 Mentor

Ad's

Posted
Posted

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.

doo doo Proficient

doo doo

Posted
Posted

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. 

mynameisdaniel Contributor

mynameisdaniel

Posted
  • Author
Posted

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.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing


  • Similar Content

  • Latest Posts

    • The Bogan
      🚨 Need Advice! Overcharged for Engineering Report 🚨

      By The Bogan · Posted

      Does that price include the rack time to straighten the frame and body and replacement of parts and paint, as well as the noise and emmisions testing  The last engineering certificate I had done, albeit about 15 years ago, was around $1000 for a few inspections and the certificate 
    • zigrb30
      R33 gtst gearbox top barb

      By zigrb30 · Posted

      😂 thanks guys. The diagram i had did not have the breather on it at all. Much appreciated.  
    • GTSBoy
      🚨 Need Advice! Overcharged for Engineering Report 🚨

      By GTSBoy · Posted

      f**k. I charge that per hour.
    • MBS206
      🚨 Need Advice! Overcharged for Engineering Report 🚨

      By MBS206 · Posted

      Geez, engineers fees have definitely gone up. Mine back 2007 cost me all of $300. Mind you, I had to go back to him a few times to get him to write the correct things on the report after he'd inspected it. Things like wrong exhaust size, wrong wheel sizes, etc etc.
    • GTSBoy
      🚨 Need Advice! Overcharged for Engineering Report 🚨

      By GTSBoy · Posted

      Can we see a scan of the original quote? The problem with engineers (and by this, I mean, all engineers across all engineering industries) is that there are "engineers" and there are "engineers" (you'll have to imagine the two different vocal emphases on those two versions of the same word. Engineering is a mindset - your farm kid who spent his life rebuilding the tractor will likely make a good engineer. The farm kid who spent his life taking photos of butterflies.. perhaps not. But on top of that mindset, the modern engineer has to learn how to write so that there is absolutely no way of being misunderstood. Proposals/budget estimates/quotations are one place where this is absolutely vital. You have to delineate your scope of supply with extremely hard boundaries, and anywhere where there is any possibility of not being able to have such a hard boundary, you need to write language that will cover you from scope creep, cost overruns, the inevitable interference of the client or their "engineer", etc etc. Now, if your clients are the BHPs and the Rio Tintos of the world, and similar, then you get good at this. If you are an automotive engineer, pitching work to the great unwashed masses, your skills in this area might not be well developed, because you're only dealing with knuckle draggers trying to get a big block legal in a Torana. And when I say "might not"....I'd suggest there's a better than even chance that any such skills might be completely absent. So, we might be able to look at your quote and see what the opportunities are for rebuttal.
×
×
  • Create New...