Head Conversion For Rb20

[Guest rwkw]

Does anyone know if the rb25 head fits onto the rb20 block????

cheers people!!

[rbs30]

Different size bore..Could probaly make it fit..But that leaves the question,WTF for?Just buy a whole rb25 or put the head on an rb30..

[Jago]

part of a PM "conversation" i had with SK in regards to this, thought it may help you out a fair bit:

Hi Phil, let me start of by saying that an RB20 head is most certainly not a “shit breather”. Some years ago we stuck a standard RB20 head (with much fiddling) on an RB30 block and picked up 40 rwkw over a highly ported and worked RB30 cylinder head with a big cam. So the RB20 cylinder head, even in standard form, is not such a bad thing. The RB25 and RB26 lovers would have you believe that, but the truth is they are actually quite good. A bit of porting and polishing of the combustion chambers, some cams and they more than capable.

To answer your question……...well you could put an RB25/26 head on an RB24 but it would be a hell of a lot of work. The valves would hit on the cylinder sidewalls at full lift, so the walls would need to be trimmed, carefully. The combustion chambers would be too large and wouldn’t seal the head gasket. So they would have to be welded up and re-machined. The squish zones would be in the wrong place and would need to be welded over and re-machined. The water jackets would be in the wrong place so they would have to be welded up and re-machined. You couldn’t use an RB235DET cylinder head as there is no oil feed in the RB20 block for the VVT and front camshaft bearings.

[TurboX]

Thanks Phil, I for one was most interested to read this.

I have extensivley modded my GTS4 RB20 head and wondered later if I might have been wasting my money and time.

By the look of SK's experience on them it was probably worth it.

On a side note I have often wondered if all of us are missing out on SK's gems in PM's and wether he should put them all to the Blog.