RB24 No, not that one

[jdmser]

I been trying to find more info on this idea I had. I read that a small about of production RB24 came with the RB25 block, the RB20 crank, and a sohc carbed head. I've been looking into boring my RB20 but, for the cost factor putting my crank into a RB25 long block wouldn't be that bad. Would this set up need custom pistons or rods? What would the pros and cons be. I've thought of some pros ie: lower compression, bigger displacement, higher revs, wouldn't have to collar another crank. There has got to be a down side to this though. Can somebody let me know what it is?

[rbforsale]

if your trying to do a hybrid rb,why not a vl comodore rb30det head on and rb25 block and make an rb33et

[jdmser]

I'm just saying I know the crank will work but, what does it take. Will in bolt right in or do you need other things.

[themadscientist]

Why? If you 400hp or less just build the 20 and roll.

[jdmser]

Why? If you 400hp or less just build the 20 and roll.

The best I've been able to find RB20 piston for is just under $800. Then it would still need machine work, head gasket, ect. I've seen RB25 long blocks for $900 and less. If it didn't need custom rods or pistons all you would have to do is replace main bearing and you got a better head and bigger bore for less then new piston in the rb20.
Modified by jdmser at 11:53 AM 1/30/2007

[rustbucket]

if your trying to do a hybrid rb,why not a vl comodore rb30det head on and rb25 block and make an rb33et

What? How does that make an RB33? You get .8 liters of displacement from replacing a head?

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^Sarcasim
Modified by rustbucket at 6:16 AM 1/30/2007

[Carl H]

wow dude, please dont post if the information isnt accurate.for starters the rb30 was a single cam motor and even in turbo form it was a sohc...people put the 25 head on the 30 block to make a twin cam rb30det.and there is no way in hell you could gain that much displacement from a head swap.

if your trying to do a hybrid rb,why not a vl comodore rb30det head on and rb25 block and make an rb33et

[Stealth-Z]

There was an actual production RB24 SOHC. I have seen them in The Philippines. They were in Cefiro's and are carburated. I even stopped in at a Nissan dealership to check part availability and prices. Not much difference between what we pay for RB oil and water pumps here.

You could conceivably install the RB20 crank and rods into a RB25 long block. You would need to source pistons. You would end up with a low CR using stock RB24 SOHC pistons as the DOHC head has a larger chamber volume. You could deck the block and or shave the head.

The RB24 motor combination was something I considered a few years ago before getting a RB30 block.

[Carl H]

yare i had heard of them being produced...but no actual proof...werd tho.if i had tons of money and for ****s and giggles i would get a rb25 with a dead crank and cram in a 20 crank like you said, you end up with a 2.5 liter in the end but one with an incredibly short stroke.the 20 comes std from factory with the 'ideal' rod ratio of 1.75, the 25 and 26 get progressively worse.to build a proper rb24 you'll need 26 crank and rods and custom pistons, cp already has done up some 2.2 pistons for the 20 and all that has to be modified is the pin hight on them.clearance the block for the longer crank throw and relieve the head and you are done; i almost did a 24 but then realized it wouldnt be cost effective.

[Sil240]

What he's trying to do, is a Short stroke RB24.We talked about this in another thread last month or so.

RB25 block, with RB20 crank.It is just a BIG BORE rb20 or a Destroked RB25. 86mm bore x 69.7mm strokeIt would be a very Oversquare motor.I would be very interested in seeing performance on one of these.

What head would you use though??

[Stealth-Z]

What head would you use though??

Depends on the RB25 block. I believe the N/A blocks do not have the vct oil feed to the head cast in.RB25's have a few variations.

[Sil240]

OH really...Didn't even think about that.Well is the oil feed in the block circular?, because you could maybe just plug it.

But thinking about it now.You would have to use the 25 head, or maybe the 26. but the 26 is a little harder to find, plus more $$.

[Carl H]

dont forget that if this motor is gonna see big revs then perhaps the de block isnt ideal because it lacks the big nasty crank girdle that the turbo motors have.altho if you have a parts rb20 you could just use the crank girdle from that on the 25 block...

[Stealth-Z]

OH really...Didn't even think about that.Well is the oil feed in the block circular?, because you could maybe just plug it.

But thinking about it now.You would have to use the 25 head, or maybe the 26. but the 26 is a little harder to find, plus more $$.

Going the 26 head route means drilling and threading for larger head bolts.The RB30DET guide here...http://www.geocities.com/rb30_twincam/has some photos of the oil feeds.

Carl, Good info on the RB25DE not having the full crank girdle. Did not know that.

[Carl H]

whoops i stand corrected, the rb25de DOES have the crank girdle but the rb20e lacks it...just flipped thru the engine manual to verify.looks like the twin cam motors are setup with a main girdle...

[jdmser]

So the rb25de block and head would be a go? What rods would be needed? Does the rb25de come with piston squiters?

Oh, and if the rb25 is anything like the ga16 in regards to the vct all I would have to do is replace the cam gear with the intake cam gear from the rb20.

[Stealth-Z]

So the rb25de block and head would be a go? What rods would be needed? Does the rb25de come with piston squiters?

Oh, and if the rb25 is anything like the ga16 in regards to the vct all I would have to do is replace the cam gear with the intake cam gear from the rb20.

Use the RB20 rods and source some factory RB24 pistons from The Philippines.Not sure about the piston oil squirter's on the RB25DE.

Seems like you are on the creative motor building path...

[jdmser]

And just to make thing more complex, what about the rb25de neo motor w/ rb20 crank using rpm switches like the sr20ve guys.

[Carl H]

lol if i had a neo motor i wouldnt eff with it at all, it has gtr rods std and beastorz pistons. that bottom end will hold 600whp reliably all day.

[jdmser]

Even the de? The long blocks are cheap as ****.