Which Intake Manifold for a 240Z???

[spawpoet]

My brother and I are getting a new set of SU's for our 240, and have a question regarding which manifold to use with the carbs. I know 240's came with n-46, e-88, and n33 manifold at various points in it's production. I've read the general internet conjecture about these manifolds performance, as well as the n-36 manifold that came on the 260z's. We have ALL of these manifolds available in our shop to use. I'm skeptical that there will be a substantial difference in performance between them, but curious what the wisened community here feels on the subject. I.E. which manifold would you guys use?? The engine we bought our car with (an ITS 240) is to our knowledge bone stock. Also i'm curious what needles you guys are running, and if you are just using the standard 20w oil in the dampners or if you might have any other advice regarding the carbs. Thank you in advance for your comments.

[spawpoet]

Bueller??????

Bueller????

Does anyone have an opinion on this?

[x-ring]

Dunno. My car is a 260, so N36 is it for me.

[Ron Earp]

I wish I could help you but I have a 260Z as well, so I've never paid attention to the Z choices. I bet Katman or Steve P might have an opinion when they login, but they aren't daily on the site.

Ron

[Parrish57]

This is all just opinion and regurgitated lore since I haven't put any of it to flow bench testing. I'm told that the N33 flows better than the others. I know of guys who have taken numerous examples of each to a flow bench and picked the one with the best numbers. Not all intakes are the same, even if you are testing one E88 against another.

As for the damping fluid I took the advice of the guys at Z Therapy and use ATF. And not very much of it at that. Just enough to get the plunger wet.

The needles are a tough one. The prep level of your motor will affect which needle works best. I would defer to Katman, if he logs on, but I use a stock needle from the early (70) Z that is "custom ground". (by that I mean that I hit them with a grinder a little at a time during a dyno session until I got the best result). I know that there is a lot more to be had by having needles custom made and dyno tested, I just don't have the time.......

[kthomas]

E88 or N33, whichever you have that's prettier. Rebello used to claim 10 hp or something stupid like that. We couldn't show enough difference on an east coast dyno to matter. Our ARRC wins were with an E88.

Needles- they need to look like a telephone pole. More metal, not less. SM's, N27's and anything "ground on" will be too fat. N27 was stock for 1971, N54 for 1972. I think we ran something closer to an N58. With everything in perfect blueprint (bottom end, valve placement, cam, and carbs) and a decent header, you'll be too fat up to 5500 rpm and too lean past 6800. So we slow the suction piston down and live with a little leanness over 7200. We used [secret] for the damper oil, so 20w or 10w30 is fine. I don't believe in lighter, like ATF. Makes the piston come up too fast and runs fat.

Now the old school thinking was get the piston up quick so there's no restriction. ATF for damper oil was the rage back in the 70's. Ive found that it just doesn't make horsepower that way. Rich mixture will cure a lot of ills, for example you can run zero point gap (if you had points) on a Z if you put enough gas in it. But if the rest of your system is blueprint you don't need to be rich, you need to be lean. Mixture control is more important than flow up to about 6800. There are some very competent Z pilots out there running the Rebello method of no oil whatsoever, so the piston slams up to the top soon as you crack the throttle. Those guys never beat me. And my car idles and drives around the pits without spitting black smoke all over the place. I like my way.

In the end you need a bigger jet to take care of the over 7000 lean problem, but then you're in for custom needles. It isn't really a problem, you won't melt a piston, but there is a few more horsepower up there to be had. The stock jet limits you. But having said that you should be able to win races with everything perfectly stock, and we never made it to the bigger jet part (we ran to 7400 rpm at Road Atlanta, 7200 tops anywhere else).

You really need a good O2 sensor on each bank (I used cyl's 2 and 5) and a HAL30 or similar lambda or air/fuel sensor. We were fortunate to do our tuning with a proper engine dyno, but if I was on a budget I'd put the instrumentation in car for test days when you can look (I've decided driver's don't see anything during a race unless it's a big blinking red light).

Headers will affect mixture, so YMMV.