Why RB25 block with RB20 head..

Discuss the RB20, RB25 and RB26 series engines.
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Audi TT

Why RB25 block with RB20 head..

Postby WantingASkyline » Wed Dec 12, 2018 9:26 am

RB25 block with an RB20 head and a Garrett GT3071R

So I have read online how terribly hard it would be to put this combination together but apparently someone did it. Not sure why but that is why I am here. Other than remarks that aren't helpful to the discussioin, could someone tell me what benefit this would have if any? If the changes were difficult I would assume that changing over to the 25 head would be a pain in the as* or not feasible at this point?

Thanks in advance. :confused:

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Re: Why RB25 block with RB20 head..

Postby RRRRB » Sun Dec 16, 2018 10:07 am

No reason to do this, RB20 heads flow substantially less than RB25 heads, bore size between the 2 engines is different and some combustion chamber work would likely be needed on the 20 head.

The 20 Head would likely perform worse on a 25 block due to the increase in flow potential from the additonal displacement.

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