RB block

[rs13]

Do anyone know if the block on rb20/25/26 is the same with different bores?Ore are they totaly different blocks.

Christian

[themadscientist]

different, all of them.

[rs13]

In what way? is it the same block with different cooling/oil ports?Can a rb 20 block be borred out so rb2526 pistons fit?

Christian

[SeVa-S13]

The RB20 can be made to accept both pistons and cranks from the 25/26.As for specific block differences, I'm sure TMS'll get back to ya.

[themadscientist]

They make kits to punch the RB20 up to as high as 81mm. Beyond that I would be leery, 3mm is a heck of a punchup. The RB25 and 26 share the same 86mm bore but differ in stroke. The two cranks also fit the 20 if you want to make a stroker. Word on the street has it you can use a 26 crank with some Toyota 4AGZE pistons to stroke the 20. I have heard this from several reputable people but having never actually done it myself I cannot guarantee it just "goes together". The 20 and 25 have one oil drainback it the block whereas the 26 has two, the head gaskets are different between the three; water passages and oil drainbacks and some say certain heads won't go on certain blocks but Dremel makes wonderful rotary tools;)

[themadscientist]

3.14159265 x [(bore divided by 2)x(bore divided by 2)] x stroke x # of cylinders divided by 1000

[themadscientist]

RB20 69.7RB26 73.7

with stock bore 2.1, 82mm 2.3

[ceniack]

As far as I know, using 82mm pistons and the GT-R crank makes the RB20DET a RB24DET...just swapping the GT-R crank in allows the RB20DET to become a RB22DET if I remember correctly....Christian probably knows best as he does the math on this crap all day long lol...RB20 Freak he is, gotta love enthusiasts!!! =o)

sorry to revive an old post, but what would putting just the GT-R crank in do to the compression of the engine, or is that all in the actually pistons. (wouldn't it lower it?)

[PROJECTRB240SX]

actually it'll raise it because the pistons will go above the deck height..... you will need to put either a head spacer or get pistons that only go to deck height.

[ceniack]

you will have to actually replace the pistons and rods anyway won't you? (sorry, i am kind of a newb to engine internals)

the reason why i am asking is because i am in the process of looking for an S13 fastback non-running for the purpose of an engine swap, and i am trying to decide between the RB20DET and the RB25DET.

by stroking the RB22DET to an RB22DET i think that would not only make the swap a little more unique, but also i think i could do the swap for alot less money depending on where i source the clip and what not.

*edited for typos*

[PROJECTRB240SX]

the rb20det wouldn't need to be storked to a be a rb22. the rb20det to rb22det conversion is done by enlarging the pistons to 82mm. The rb23det uses the rb25det crank and rods with custom 82mm pistons. The rb24det conversion uses the gtr crank and rods with custom pistons. There is also a 2.5L conversion using the gtr 2.7L stroker kit and custom 82mm pistons.

[goofynick6]

just buy and rb25 shortblock and save the time/money..heh

[WDRacing]

Or...check me out....buy a real stroker kit...lol. Paeco makes some pretty good stroker kits for real decent prices. Plus you can get the block punched out and have some forged sleeves thrown in so you can over bore the **** out of it. I'm willing to be I could get the RB26 damn close to the RB30. Or just have a RB30 shipped back from Aussie and do a head swap, for like 1/10 of the cost.

The point to the whole post I guess is, just buy the RB25 or 26 if you want the extra cubes. Cause in the end, it saves money. Another thing you guys have to remember when stroking an engine. You gain alot of torque, but you lose some of the safe upper rpm band. To keep the revs high on a stroked motor will put horendous tensile loads on the rods. This is the reason alot of people lean away from the RB26 stroker kit for Jun.

WD

[IvoryJ30t]

if your going for revs, i would choose the rb25. it has a shorter stroke than the rb26, all you need is some solid lifters and harder valvesprings.

[WDRacing]

I'll take the 25 over the 26 all day...

[IvoryJ30t]

why, because of the twins?

[rbsileighty]

I'll take the 25 over the 26 all day...

Why? Not attacking your opinion... just curious.

[WDRacing]

Lets look at the price tag compared to the benefits...I'd also convert to a big single right away, so the whole twin setup gets canned right off the bat. I don't know of any RB25's with oil starvation problems...ahh....the only thing I actually see better is the intake on the 26.

WD

[NISMO_RB25]

good to know, I hadn't really thought about the lak of an oil starvation problem in the RB25. Makes me not envy the RB26 owners at much For the price difference between the motors, you could get an aftermarket plenum for the RB25 anyway.

[rbsileighty]

I still like the 26 for it's solid lifters, higher factory redine, twin turbos (powerband), individual throttle bodies (better for road racing), and factory beef (like the crank). This is not to forget aftermarket support. Wouldn't the oil starvation be fixed with the rwd conversion and the 25's oilpan?

In the end... whatever floats your boat. There is nothing wrong with enjoying different things.

[WDRacing]

Its the oil pump thats bad, the RB25 can rev, its needs better cam profiles and a better intake. The cams and intake are designed for low end grunt.

WD

[rbsileighty]

Its the oil pump thats bad, the RB25 can rev, its needs better cam profiles and a better intake. The cams and intake are designed for low end grunt.

WD

I figured it might have been the oil pan since I see a few companies make baffles for the 26s, but that makes since b/c most big companies wouldn't make high capacity oil pumps for just the 20 or 25 due to the low volume of sales (not exactly the in and out job of changing a pod filter).

It seems lots of the major parts you can buy for a 26 are also available for the 20 and 25 (other than turbos). I assume these parts were a byproduct of the 26's shortcomings discovered in its racing history.

[PROJECTRB240SX]

THE ONLY THING I WOULD DO ON MY RB20 IS OVER BORE IT 4MM TO 82MM AND SLEEVE IT. THIS WILL INCREASE THE PISTON DISH ALLOWING FOR HIGHER REVS. NOW BUILD A MATCHING HEAD AND FORGED RODS WITH A HIGHER VOLUME OIL AND WATER PUMP AND YOU GOT A 10K RPM REDLINE..... WELL IF ALL GOES WELL. JUST USE THE LIGHTEST/STROGEST MATERIAL POSSIBLE AND BALANCE THE ASSEMBLY AND KNIFE EDGE THE CRANK. ALSO UPGRADE TO A LARGER OIL PAN FOR INCREASED OIL PRESSURE.

[GTR Shop]

if your going for revs, i would choose the rb25. it has a shorter stroke than the rb26, all you need is some solid lifters and harder valvesprings.

Say what??? you a crack head???

The RB25 is the LEAST reviest.. the has the WORST rods in it also.Soft Limit of 7krpm as opposed to 8k+ of the 26.

[GTR Shop]

Alot of the 26s oil problems stem from the oil not being able to drain back from the top end fast enough.Fixes include external drain or restricting the main gllery to the top end.