Intake manifold runner question

[Darkwolf]

are the 280z runners larger than the 260z?

I found 2 pristine SU's but they have the 260z runners.

[Bruce Palmer]

280's were fuel injected

260's had flat top smogger Hitachi carbs.

What's the question again?

[Darkwolf]

Not all L28's are fuel injected. Since I have an L28 that is dual carburated on my motor stand

The SU carbs I found are bolted onto a 260z intake manifold runner. The claim is that the intake runners from the 260z are bigger than the original intake manifold runner.

So the question is, is it really bigger or not.

[Bruce Palmer]

If you have carbs on a 2.8 are they round tops?

What is the number cast into the manifold? I guess knowing the numbers on both manifolds would help.

In the age of degrading FI systems it's not uncommon for owners to switch to carbs on these engines whether in their 280s or when putting 2.8 motors in earlier cars. In any event I'm guessing what you have is a 240 setup on a 280 engine.

The configuration of the manifolds inside is a little different with the flat top manifold appearing to be a little more open than the round top manifolds. What this relates to in the way of performance gains to my knowledge has not been documented. Just looking at the two would suggest, to me at least, that the flat top manifold might flow a little better. Other than that I know of no differences runner wise.

[Darkwolf]

I will get those numbers when i go to the shop. yes they are roundtops

Yes i have a 72 240 with an L28 removed from the engine bay for restoration work and partial rust removal. From my small research It appears that a couple other cars nissan made had carburated L28's So my L28 may not even be from a 280z to begin with but

i will get those cast numbers and get back to you.

Im going to agree that it most likely has 240z carbs.

Edited October 22, 2011 by Darkwolf

[Bonzi Lon]

My notes show the following intake numbers on the year used, approx.

E46= 69-71 4 screw SU

E88= 72 3 screw SU

N33= 73 Flat Top

N36= 74 Flat Top

Bruce is right on with the info that no documented numbers are available, ie flow rate & cc volume. However, the internet conclusion is the N36 is the intake of choice, performance wise, with round tops, bigger cam...

Bonzi Lon

[Bruce Palmer]

And as they say in the funny papers..... Once it's on the internet, it's fact, if not law..... Nyuck nyuck

[Z train]

It appears that a couple other cars nissan made had carburated L28's So my L28 may not even be from a 280z to begin with.

This would be false.At least in the U.S.

Read up on port velocity,cylinder filling & the lke.Then you be able to answer your own question.

[Darkwolf]

Well I passed up on that deal for those carbs, Since our trip did not go as close to where they were being sold as i had thought.

Thanks for the help though