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Rb25de + My Rb20det Head = Rb25det?

1400r

By 1400r,
in Engines & Forced Induction

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1400r Veteran

1400r

Posted
Posted

Hi guys this may have been covered so sorry if it has

but a mate is looking to buying a complete rb25de from a 32 then taking the head only and building a 3lt

Im wondering if I can steal (borrow) the bottom end to build a rb25det for my 32 while retain my head sensors etc so I can still get a remap cheap. Seeing as my mate wants to build a rb30det I figure he could probably easily put together the 25 for me I understand it wouldnt have oil squirters? but should I also change the piston to rb25det stock items.

Basical I want a engine similar to Darren Appletons laurel's and I think this is probably the way it was built?

It sounds like a cheap option to get some extra torque but if it would end up costing heaps then I wont bother. Thanks

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https://www.sau.com.au/forums/topic/87711-rb25de-my-rb20det-head-rb25det/
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blind_elk Grand Master

blind_elk

Posted
Posted

The combustion chambers in the RB20 head are way too small (both in volume and diameter) for a RB25 block. Compare the bore sizes of the RB20 and RB25.

You will probably have way too much comp ratio, and the pistons will likely keep smashing into the head around the edges of the combustion chamber.

Baz Experienced

Baz

Posted
Posted

I think compression would be one of the issues with that sort of conversion. The clearance at TDC of the DE would be lower than that of a DET one but I'm not sure what sort of clearnace the RB20 head may give to add to the compression?

Definately interesting conversion though. You will have to take in the pro's and con's of the DE vs DET block and whether the RB20 head is up to the task of flowing enough air.

Look into it

Cubes Grand Master

Cubes

Posted
Posted (edited)

RB30 isn't expensive if you are rebuilding a motor anyway.

I'd have to say its also quite a bit cheaper to build than to buy a RB26 and slot that in, only benifit of the rb26 is it already has turbo's, chances are they will spit though, as they do. :)

It depends if you are happy with an unknown second hand motor with unknown kays or you would rather have a nice fresh motor.

RB30 bottom end is $100

Bottom end rebuild can be done for $1800

Rb25 head - $750-$1000

Fit head and timing belt - $232

Engine mount mods if you don't have a gtr style plenum - $70

VRS gasket kit $260

$3462 + labour if you don't drop it in yourself.

Or.. Do the same to an rb25 or rb20 and it would cost very similiar. (minus the rb25 head purcahse)

------------

You can't bolt the rb20 head on the rb25 bottom end.

The Rb25de n/a also doesn't have oil squirters, not that its an issue if you are using forged pistons.

The R32 rb25de head uses all the same rb20 sensors so yer. :)

Edited by Cubes
Cubes Grand Master

Cubes

Posted
Posted

Possibly.

I wouldn't go to the trouble to be honest.

VLT's don't run oil squirters and they have well and truely proven their reliability.

R32 RB25DE bottom end and top end. Bolt it in the r32 and everything hooks up as per the rb20. It also runs on the rb20 ecu, my rb30det even ran on the rb20 ecu without any issues until 6-7psi.

  • 3 weeks later...
ebola Proficient

ebola

Posted
Posted

I read the topic carefully... you people are not answering the question.

can a rb20 head go on a rb25 block?

I am also curious - swap the block (keep the rb20det head), or use a mix of the two engines (use the rb20 crank ~= 2.4L, lower CR, more valve clearance?!?)

I would like to know - about to come into possesion of an rb20det awd, and am looking at different possibilities.

-ebola

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