RB26DETT intake manifold to RB20DET

[uber95]

I have searched 6 pages of info and not come up with what I'm sure has been asked and answered before. I'm sure someone has done it, or thought about it. Using and RB26DETT intake on an RB20DET. I want to alleviate the convoluted I/C piping and not spend $600.00 on a Greddy intake manifold (IF I can ever actually find one!!) Hoping to also scrounge some low end response back (by virtue of velocity) with the ITB after loosing my runner length by swapping to that style manifold. Thanks fellas

[Sil240]

If you have access to a CNC mill the your set.

You need to make a adapter plate.I think Blitz used to make them, but stopped.

The plate must bolt on to the RB20 head and have a bolt pattern for the RB26 ITM.

If you make one let me know I'd take one.I know of someone who made one.An older guy, met him at NOPI nats like 2-3 years ago.

It would be nice.It would serve 2 purposes.One Front facing ITMTwo Intake spacer, you'd get a larger area/volume for your intake.

[002-M-P]

I'm not sure the second purpose would work the way you are thinking it will. The spacer would make the intake runners longer, not truly increase plenum volume, because the added volume is not a common space for all intake air.

[uber95]

Runner length = Torque, which is what I'd be sacrificing by loosing the stock RB20 intake. a spacer/adapter would not equate to much length, but every little bit will help.

So it's not a simple matter of a possible bolt hole elongation and adaptation?

[Sil240]

They both work the same way.

We were going to make them, and started with the 350z (plenum) but got beat out by Skunk2 and whoever else started making them.AAM or AMS cant remember.

Generaly longer runners better lower to mid range power and torque.Shorter runners better upper mid to top end power, less torque.

[jobestudios]

Basically already stated, it's going to be **impossible** to find a blitz adapter kit, so your best bet is to go custom adapter plate. I'll be doing it this summer, going to keep the cad file on hand so if anyone else ever wants one I can get another cut. My main concern is makeing the adapter runners flow smooth, the a/f mixture is combining right there and some turbulence could cause some serious issues.

[Sil240]

Jobe if you Get is CNC'd then you wont have to worry about smoothness.If its a good shop then the finish will be good.Plus if it is a little rough just take a little sand paper and smooth it out.

A little turbulance is ok though, it'll help the Air and Fuel mix.

If you can make it out of the Phenolic material that would be great too. It would keep the heat away from the ITM. (well at least the heat directly coming from the head)

[jobestudios]

Yeah, I'm looking into some of the local shops to see if they can make the ITB gaskets out of the phenolic material, I probably wouldn't want the whole adapter to be it tho because It's going to be 3-4 cm's wide and I hear those gaskets have some problems with leaking and it would only make it worse to have it hanging out there that far.

I'm not so much concerned about the surface condition of the adapter but more the difference in the shapes of the runners and how to make them transistion properly maintaining the *vortex* of the A/F mixture