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RB25DET build advice

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Hi all,

So I'm soon going to start my engine build and I'm looking for a bit of advice from those that have some more experience (with RB's) in regards to the recommended clearances.

First some background information:

The engine is a RB25DET, it will be running 87mm, 9.0:1CR forged pistons from CP with the upgraded piston pins.

I'll be running a Precision 6466 turbo and looking to push it to around 30-34 psi and hoping for anything between 700-800hp.

Fuel used will mainly be pump gas(98 octane) for the street and pump gas (102 octane) or some racing fuel for drag racing.

I also have a nitrous kit which I'm planning to use for a small shot of nitrous (50 shot, wet) to help get the turbo into boost quicker on the drag strip.

The car will be used as a street car and for drag racing, hoping to get it into the low 10's possibly high 9's.

So in regards to the clearances, any advice on:

- Piston to wall clearance - CP calls for .0035 is this okay for my setup or do I need to increase this?

- Ring gap - CP's chart recommends for street/hi performance bore x .0045" and for drag/road racing bore x .0050" and then nitrous/turbocharged bore x .0055"

Which of these recommendations would be the most suitable for my build? Taking in account that RB's love to have blow by and I would like to minimize that as much as possible while still keeping it safe if I can.

- Main and rod bearing clearances.


Hello i have had a fair amount of experience with these engines cps recommended clearance is fine for bore clearance I prefer .018 for the top ring gap and .022 for the 2nd ring for what you are doing

Regards Ross