S.U. Intake Options

[RDHULL]

Does anyone have any hard evidence as to which factory SU manifold is better than another? I have them all and I don't want to do a trial run on each.

Roger

street legal 72 240Z historic rally car

[Arne]

That's always been the trouble, no one has (to my knowledge) done any documented testing. It's all just hearsay.

Some day someone needs to buck up and do this. Same car, same carbs, same everything except the manifolds. Dyno runs for each would be the best way to prove or disprove.

[clayton 260z]

hearsay says the N36 intake should flow beter but as Arne says there is no documented proff of that.

Mike

[Zs-ondabrain]

Where's Bruce when ya need him? Check with www.ztherapy.com

[Bruce Palmer]

I be right here waitng to see if there is anything forthcoming that'll quantify an answer.

All I can add is to suggest setting an early manifold and a late manifold side by side and look in the intake runner and compare one to the other. The later manifolds are more open inside than the earlier which tells me at least that they (the later manifold) will be less restrictive.

Whoever did the developmental work getting the flat top carbs ready for production might have sensed a need for better flow to get them to work, who knows. Makes a certain amount of sense to me that a lesser carb might require a better manifold....... Get ahold of NISSAN and ask them for the flat top development file.... Like that didn't go in the trash some years ago.

Pretty much covers what I think I know. If that doesn't scare you a little, it ought to!!

[RDHULL]

Thanks, guys. Just about what I figured, I'll go with Bruce's idea. I do know that velocity is important on anything but an all out race engine from the setup that I did for my 510, took the JDM manifold for the L16 S.U.'s, port matched it to the peanut head on my l20 and to a set of 3 screw Z S.U.'s, along with some needles from Bruce. A little cam, big valves, 421 header and I finally have an engine that goes AND idles well. Manifold throats are not nearly the size of the Z intakes but it works great up to about 6500rpm.

Roger

1972 rally Z