RB26 pistons in RB25

[Z-tune!]

Hey guys,

First, I'd like to say thanks for all of the great info on this site. I've been lurking around here and not posting for almost 2 years. I finally have a question that I haven't found the answer to yet.

How hard is it to put used oem RB26 pistons and rods in an RB25? It's my understanding that they are the exact same bore and are easily swapped. The thing I don't know is.. what's involved with putting used pistons in a used block with no machine work?

I've come across a pretty good deal on the pistons/rods and if it's not too complicated or risky, I wanna do it. Please let me know!

[eh?]

Hey guys,

First, I'd like to say thanks for all of the great info on this site. I've been lurking around here and not posting for almost 2 years. I finally have a question that I haven't found the answer to yet.

How hard is it to put used oem RB26 pistons and rods in an RB25? It's my understanding that they are the exact same bore and are easily swapped. The thing I don't know is.. what's involved with putting used pistons in a used block with no machine work?

I've come across a pretty good deal on the pistons/rods and if it's not too complicated or risky, I wanna do it. Please let me know!

They are not all exactly the same bore and besides that why remove cast pistons just to replace with another set of cast pistons? You'll have screwed up piston to cylinder wall clearances if you get the wrong sizes.

[WhatsADSM]

Wouldn't the wrist pin be too high in the 26 pistons versus the 25? I would assume you would end up with some undesired low compression ratio.

[Z-tune!]

I thought that pistons/rods are the same design, just stronger. I don't think the wrist pin should be of any concern. The only difference in size between the two motors' internals is the crank right?

[Cjmartz2k]

Wrong.

And the wrist pin height is different, so the piston would come out of the top of the bore. Won't work, and it wouldn't be much of an upgrade on the piston side anyways. Rods are stronger though, but you can just press them on to the 25 pistons if you wanted.

[Darius]

Right and wrong. The wrist pin height will not work woth RB 25/26 rods but the pistons will be sunken in the bores and give low compression. Wont work.

[Cjmartz2k]

O yeah, other way. I forgotz

[sickness14]

O yeah, other way. I forgotz

so is my setup even possible then? the block was built by the previous owner...

rb26 cp pistons 86.5mmrb26 rodsrb26 r33 crank

i think i spun a rod bearing sucks. engine coming out this weeek.

[Darius]

Yes, if you have an RB26 crank, you can use RB26 pistons in an RB25 block.