Rb 25 Det Head on Rb 26 Bottom end

[Chev R]

Hi Guys.

Hope I can get some help here. I have searched to try and see if I can get any info but could not get much.

If I could possibly get some info on the conversion I am considering doing please.

I currently have and Rb 25 Det engine. These are some of the Mods that were done.

Cylinder Head: Ported and Flowed

Cams cut 270

All rb 26 internals: Valves , Lifters , Retainers , Valve Springs etc

So the head is complete solid lifters solid cams not using vvt anymore.

Sub Assembly is stripped due to detonation: 1 piston in the ringlands , no 6 big end bearing spun.

So this is what I need help with please

A friend of mine offered me a rb 26 bottom end that I can fit the Rb 25 det Head too.

So some of the info that I have managed to get says it can be done. The Rb 26 uses 12 mm bolts.

But are there any other mods that need to be done in terms of water galleries and oil?

Can I use my rb 25 cometic head gasket of the block?

Or is this a straight fit?

Any input will be appreciated

Chev R

[Lopin18]

Ok this comes from recent observation of what i was doing. I have a RB26 head and a Neo 25 Head. And a 26 Tomei headgasket.

On the RB25neo with VTC, the front intake side of the head has a hole for Coolant and another one for VTC, when i matched the 26 Headgasket to it both holes get mixed. As  the HG is the same as the rb26 block, if u use the RB26 block with the 25 head i think you would have to do something about its VTC oil feed as it will receive Coolant. 

Do this, grab your head gasket, the block and the head. and try to match the HG on the Block, you will see what i mean, then try to imagine whats gonna happen when u mate both pieces, that should help you decide which headgasket to use. 

[Tristan363]

would swapping the heads around mess with compression, weather is was rb26 block/r25 head or the other way around because of dome depth on the heads?  or are the domes the same depth?

[KiwiRS4T]

Are you sure the RB26 block is in good nick? How much would it take to repair your 25 block?