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Rb25 With Rb26 Internals

B0oStEr

By B0oStEr,
in Engines & Forced Induction

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B0oStEr

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1) I wouldn't go over 1mm overbore because if you blow your motor and need to overbore the cylinders, there's 1mm of material to spare. An extra mm of diameter is not going to give you noticibly increased power anyways. I would err on the side of safety.

2) As far as swapping RB26 internals into an RB25DET is concerned, what brand of bearings are recommended? Also, shouldn't the machine shop measure the crank and rods and determine what bearing thickness is needed from that?

3) I am installing Tomei valve springs with new HKS cams (256 x 8.8mm) and RB26 rods and pistons. What is a reasonable increase in redline with this setup?

I'm not concerned about leaving material for further rebuilds because second hand rb25 blocks are cheaper than new forgies.

I'm using ACL race bearings 6B2960H std, 7M2394H std as my crank measured well within stock tolerances.

I don't know if upgrading valve springs will really do much to raise the redline because I think the redline is limited by the hydraulic lifters.

That's not to say the heavy duty springs are a waste of money as they are necessary to control the valves with more agressive cams.

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