Rb25 Bottom End On Rb20 Q

[Nathan_G1]

Hey guys, im trying to build my R32 as a drift car and a competative one at that. I know an RB25 bottom end will go on an RB20, how much messing around is there to actually install it?........and what benefits would doing this give me.

My guess is greater torque and a better power range. But i dont know of many people who've done this, so if u have any ideas or knowledge help me out

Cheers

[FATGTS-R]

Search as it has been covered a few times.

Search "RB24" , "stroked RB20" etc.

The general consensus is that due to the costs involved to do it its not worthwhile as you could have an RB30/25 in there instead for the same if not less money.

[Cubes]

Generally.. Well in this case...

Increasing a motors capacity without touching the head will see the power band shift to a lower rpm, the motor will make its peak power earlier and power will drop off harder and quicker than the smaller motor.

Not that thats a bad thing as you are only looking at another 400-500cc's.

If this were to be a 3ltr under the rb20 head I think the overall performance of the car will suffer due to the lazy less revy motor.

Edited November 19, 2005 by Cubes

[R31Nismoid]

i dont think there is a great gain to be honest without a LOT of head work for the RB20...

which just using an RB25 outright would save and give you better bang

[Nathan_G1]

Cheers guys.......maybe il just stroke my RB20 then, RB26 crank and conrods and probly sum forged pistons to get it to 2.4ltr, that'l probly b a little better

[carl h]

Cheers guys.......maybe il just stroke my RB20 then, RB26 crank and conrods and probly sum forged pistons to get it to 2.4ltr, that'l probly b a little better

<{POST_SNAPBACK}>

the problem is that the rb20's head flows like poo.

compare it to sucking thru a coffee stirrer and then sucking thru a large bore straw, the large bore straw is significantly less restrictive.

increacing displacement without modifying the head is almost a back step as now the motor has the ability to suck in more air but the air to be had isnt there due to the restrictive head.

oh and fwiw a rb25 crank and rods yeild 2.3, a 2.2 can be had by an overbore.