So since no one has really pushed these engines I guess I will be the first to do and then record. The engine build is as follows:

Stock RB20 block and tranny

Running E85
Upgraded Clutch
HKS head gasket
Brain Cowler Cams
Top Mount Turbo Kit
-T3 top mount manifold
-T67 turbo
Custom Down pipe
Blitz 3.5in exhaust
HKS drag FM intercooler and piping
Apexi Power intake and funnel
850cc Injectors
460lph walbro e85 pump
Aftermarket A/F, boost, and oil pressure gauges
Nismo short throw shifter
Nismo cluster
Apexi Power FC with boost controller kit
Greddy BOV
Tial 38mm external waste gate
Atmosphere dump
Dual core racing radiator
Racing thermostat
New hosing
Upgraded TB and cable
Z MAF
All truck carpet removed

So what numbers u guys wanna place down on this build?

No one pushed an RB20?? Guys have been doing it for awhile now. It's not like they've been around for 30 years...

How is "trunk carpet removed" helping your engine build? Lol. Take that off your mod list.

Lol my bad I didn't even notice I put that, no I know they have pushed them but the best I have read is 498 to the wheels I think these engines can do better that's my classification of pushing it more then I have read in less someone else can show me they have made better then 498 on a all stock block???

Before the 25 came along I saw some pushing high 300hp-low 400hp, but that's it. That head doesn't have the flow for much more without a lot of work. Never seen or heard of one pushing near 500hp and ones in that neighborhood are sure to be 2.2-2.4 strokers. At that point you might as well have a 25 that can actually live there for more than one weekend.

Yeah I have read that all over the forums, here, SAU, GTR Canada, and skyline owners. Everyone wants to play with the 25/26 but just saying forget the RB20, but Idon't I just have a gut feeling that I can make it work with this motor and show it's still a RB and Nissan still originally used it so u can take that away, plus I mean P/W ratio low 400rwhp is still decent for a car weighing ~2400lbs in terms in should be my Shelby that is only making 648rwhp cuz the weight offset. But if worse comes to worse rebuild with RB26 internals or just buy a Tomei 2.8 forged race block for it you know.

I'm not saying forget the RB20. When I got to Japan in 94 there were seriously pissed off RB20s that were gnawing on stock GT-Rs with extreme malice. I'm just saying be aware. The amount of work and money you will put into the 20 is the same as what you would put into the 25 and 26 and you will get less back for your investment and it will be less reliable because its wick is turned up higher to do it. Also, you are not putting 26 slugs into a 20 block unless you want water-cooled pistons. the crank should go with the 26 girdle.

If you want to try something goofy, you could build one of my ideas. I've never been pleased with the short deck on the RBs and stroking them, IMO is the wrong way to go. I feel the same way about my lil CA18. There is a lot of piston skirt dragging up the cylinder walls at those inefficient rod angles and all people want to do is spin it even faster!

The RB20 is a 78mm bore and a 69.7 stroke
The RB26 is an 86mm bore (starting to see why the 20 block can't handle it) and a 73.7 stroke.

I'd have to check my shop manuals, but I'm almost positive the deck heights are the same. If that's the case, the 20 has the better rod angle, meaning, the piston is pushing more linear to the crank thus losing less power to friction on the cylinder. There's no denying that displacement matters, though, so the etra 600ccs are making a difference.

What if you took a 26 block and dropped a collared 20 crank (the 20 has the same oil pump drive problem as early 26s) in it? You would have to have custom rods done up, but you could retain the 26 pistons and have an RB24 with better top end.

That sounds like a awesome back up plan when this engine goes out but my problem is finding all the parts and shipping them to me sense these cars just barely becoming legal in the US so what would you suggest for that?

Somebody has to be shipping in 26s still. You need a block and head. The only flash parts you would need is custom rods. The crank collar, uprated oil pump, cams, pistons and such are all readily available in the aftermarket brand new.

I've been vetting my silly idea around the internet. Here is a 20 rod next to a 26 rod. They are the same length and pin size. Notice the difference in big end size, though.



I also stole this which shows the rods being the same length. They make up for it in pin height.

RB20
====
188.5mm Deck Height, 121.7mm Rod, 21mm Pin, 32.0mm Comp Height, 78.0mm Bore x 69.7mm Stroke.

RB25
====
188.5mm Deck Height, 121.5mm Rod, 21mm Pin, 31.5mm Comp Height, 86.0mm Bore x 71.7mm Stroke.

RB26
====
188.5mm Deck Height, 121.5mm Rod, 21mm Pin, 30.0mm Comp Height, 86.0mm Bore x 73.7mm Stroke.

Were I you, I would have custom rods made with the RB20 big end size for use with the shorter compression height RB26 pistons. This will give you and even better rod angle with the extra 2mm of length in the rod beam.

Yeah there is a way to ship it in, but the customs on this engine is ridiculous to get here actually but I'm sure I can find a way. So my next question to this insane yet very interesting build we are talking bout is, who would do the custom fabrication to the internals to get this right? Cuz I already have oil pump and cams inside the engine as of right now.

Unless there a main journal differneces between the 20 and the 26 crank (be sure to check sizes) the only custom part is the rods and any competent rod maker can do you up a set to your specs.

And make the rods the same length as the 26s but size of the 20s right and use the 26 block? That's what we're talking bout right? What bout pistons though?

No, the difference in the respective crank strokes is made up by moving the piston's pin height. If you use stock 20 rods with the 26 pistons on a 20 stroke the piston will be 1.8mm below the block deck at TDC. You will have like 2:1 compression!

No, stock 20 crank, stock 26 pistons, and custom rods with 20 big and little ends and a longer beam to get the piston to the top of the bore with the shorter stroke.

Ok that makes more sense in retrospect there haha so what should the RB20 block be bored out to then?

No, you are using a 26 block and head. the only 20 part is the crank.

Guess time to start shopping lol anything else u recommend

Keep the coil cover off so the coils can breathe.

Great discussion - I've driven a few hopped-up RB20 cars, and you just can't beat the smoothness of the inline RB...

Mike (TMS) has some great knowledge, and RB stuff isn't all that pricey to get hold of. Hit up Carl H (here), he's an RB20 tuning whiz. Also, RawBrokerage probably has some spares laying about as well.

Awesome already did that when I changed the coils out to aftermarket Spit Fire's. Any other suggestions.

Thanks for the info AZHITMAN I have been trying to get a hold of Carl H for the longest time to tune this car but no luck so I'm having DVS tune it for me out of Wales haha

Watch the #6 exhaust stud. The manifold grows unevenly under extended full throttle runs like on the highway for a mile and it can snap the stud on #6. Other than that I've never had a design problem on an RB20.

Will do buddy, well today I finish building it up and tmmrw I tune it with DVS so moment of truth haha

Kind of going back in the other direction, but I'm getting ready to disassemble an RB25DET for scrap, a perfectly running one that nobody wants for some reason. You want to buy the rotating assembly or any other bits off it?

I would love to, but as in for the build we were talking bout there is really nothing I would need from the block though is there?

You could use the block, there are enough huge power 25s to say the 25 block is tough and the head as well flows powerful amounts of air without trouble, but I can't get it to you.

Can't get it to me how?

I live in Japan, I assume you don't. Am I incorrect?

I might be able to mail a naked head, but that block isn't going to make it.

Ur right to ur assumption I live in the US I brought in the second skyline to the US and had it legally registered here. I'm sure if I was to buy it there would be a way to crate it cuz I found a bare RB26 block from New Zealand for 600$ and then 125$ forshipping of it. Question for you I just upgraded my radiator to a racing on e and it has no tap for the thermo switch any more I can disconnect that bad boy and still run fine right? Since I have no ac system and my fan is a slim fan attached to a manual relay switch.

A quality drop in radiator should have the bungs for the sensors. With all the folks making parts for the car there's no reason to go with a universal unit that universally requires you to do extra stuff to make it work.

Well I mean the radiator is blitz and it has the bung but it's to small of a thread but I was reading that sense I don't have as fans or ac and have a manual relay switch that I really don't need the thermo switch at the bottom of the radiator in less I wanted to fit it in....just trying to confirm my reading