Difference Between Rb20 And Rb26 Head

[ChrisOk1]

I'm looking to buy an RB26 head and I've received a message from a guy about his RB26 head. He's got RB20 cam gears on the head currently and no cam covers but it's made me a bit sus about the whole thing. Is there any definitive way to tell the difference between an RB20 and RB26 head visually?

[r32-25t]

Rb26 head has 05U cast in the side of it

[Piggaz]

It will say "05U" for an RB26 head above number 1 exhaust port.

Zoom in.

[ChrisOk1]

Legend!

[iruvyouskyrine]

RB20 has 76mm pistons and RB26 has 86mm pistons so the hemispherical part of the combustion chamber in the head would be the appropriate sizes.

[r32-25t]

All the water jackets don't line up either,

But he wanted to know how to tell easily and the 05U is the easiest way

[iruvyouskyrine]

Yeah but OP already said he was suss on the whole thing being a little dodgy. That is something that you can't fake

[jiffo]

And the real simple one, orientation of the studs on each exhaust port.

26 has symmetry, the other Rb's are just weird.