[Spitfire]

hi there people

I have a little project in my mind... something i wont be able to build sooner than in lets say 4 5 years, but I was thinking about it for a long time already and I just simply cant get it out of my head.
Im planning to bult a n/a R32 coupe with approx. 230-250hp :smokin: but which engine should i choose as a base? the RB20 or RB25? Ive heard that these two engines are quite different in their construction, can anyone please specify that?
the 25 logicaly seems as a better thing to begin with, but I think the RB26 crank and other internals can be used in the RB20 to generate up to 2.4 liters of displacement, how much true is that?

thanks everyone for help

 

[moNoKnoT]

Go with the engine designed to be n/a. That way, compression ratio's, cams etc are already geared to the na setup.

- Kevin.

 

[SAMFISHER]

Check out Best Motoring International Vol 5.
It features an N/A R32 with, IIRC a 2.4 RB20.
Not too many modded N/A's about so definately unique.

 

[Warpspeed]

For any n/a engine, the key to reasonable power is airflow and engine breathing. The RB20 and RB25 are totally different engines. Thr RB25 has larger cylinder bores and the cylinder head has VASTLY better breathing potential than the RB20 cylinder head. The heads will not interchange between the two different blocks because the water passages around the bores are in different locations.

The RB25 will give you an extra half litre of capacity, and is a much better basis to begin from. RB26 crank (the rods are the same) will drop straight in, but some special pistons will be needed because of the different pin height. The extra 1.3mm stroke and 100cc hardly seems worth the trouble and expense, unless you happen to already have the parts.

 

[Spitfire]

Thank You very much guys for your help :bowdown1: