rb20 w/rb25 head?????anyone heard of this

[rb20detsilvia]

is it possable i did search

[klh6686]

i don't think so, google a rb25 and rb20 bore size and compare. btw please search MORE next time you ask a question like this. Im not one to flame, but common man.

[Valley]

it will bolt on, but it will not work. the rb25de chamber is larger than the rb20, and the rb25det has vtc solenoid to deal with.

[David_NISMO]

Doesn't the RB20 valvetrain allow for higher rpms anyways? What would you gain from using the rb25 head other than that's all you've got lying around?

[Joe]

Doesn't the RB20 valvetrain allow for higher rpms anyways? What would you gain from using the rb25 head other than that's all you've got lying around?

rb25 head flows better

and theres a ton more factors than valvetrain for figuring out max RPM.

[Carl H]

bigger valves and much larger ports it simply pwnz the rb20 head hands down.but doesnt mean the poor rb20's head cant make any power, on the contrary it can easly make power up to about 450bhp or so then it becomes a bit restrictive.

[David_NISMO]

Cool stuff, I wouldn't have known.

I know that one of the main factor determinging max rpm comes down to the stress the RA (rotating assembly) is creating and the strength of the block and the internals to hold it all together. Balancing reduces the stress on the RA. I would guess that the RB20 and RB25 are pretty close in their ability on the bottom half to sustain higher rpms. So I just figured it was the valve train of the RB20 that allowed it to rev higher.

Althought I guess it could be the extra .5 liter too.

Thanks for answering my questions without flaming

[eh?]

I would have to say the lubrication system is the Foremost limiting factor for both engines.They both need the upgraded pumps, crank snouts, oil restrictors and head drainage.

[Yellow4g63]

I think Fito back in the day did a Rb25 head on a RB20. I remember seeing that in one of his post.

[Shahee1]

I have an extra RB25 Block in my shop right now and I was lining up the RB20 headgasket on the block and it was really damn close ... it a little work to increase and align the water passages and the oil passages but its not impossible ... maybe not cheap either ... LOL ... but the increased displacement would be welcome ... Its been hard to find an extra RB25 Head ... LOL ... at least you won't have to worry about vtc if you use different head.

[Cubes]

The R32 RB25 head doesn't use VCT and has the same bolt up (apart from the head studs) as the rb26 head.

Also do remember stroking out a motor under the same head WILL reduce peak power RPM. It will feel much like a diesel.

Very much like dropping a rb30 bottom end under a rb25 head.Leave the head stock with the stock manifold and you will make peak power on the stock turbo at around 4400rpm vs peak power on the rb25 just over 6000rpm.

I think the rb20 head on a rb25 really is a useless exercise that will leave one dissapointed with the performance characteristics of the motor. i.e BIG TURBO DIESEL