Are all 240 manifolds created equal?

[EricB]

I was surfing some fellow 240Z owner's rides on the net, and found a couple that mentionned explicitly that they were using N36 manifolds with their original SUs. What's the big deal? Do these flow better?

Thanks and Good Morning too BTW,

-e

[John Coffey]

I wish this urban myth would die, but I'll try to explain again...

A lot of time racers will find something that gives a little more power for a particular engine configuration that's limited by the sanctioning body rules. Racers will spend thousands of dollars and/or hundreds of hours trying to find 10 more legal horsepower. They exploit that something and word travels around the racing community.

Soon, street racers hear about this modification and think its some magic bullet so they apply the magic to their modified engines and feel faster. But, if they spent the same time and effort on other mods (not restricted by any rules) they will see much much greater horsepower gians.

The N36/33 manifold giving 10/20/30 more horsepower is one of those myths. Yes, it does give slightly more horsepower on a basically stock motor than the other UNMODIFIED intake manifolds if the motor is in perfect shape. ITS engine builders discovered this years ago. But, any L6 intake manifold that's had some mild porting, polishing, and/or extrude honing done will flow equal to or better than a stock or modified N36/33. I know, I've seen the hours and hours of dyno tests.

So, if you already have a pair of N36 manifolds (I wouldn't spend the time and money to source a pair of these "trick" parts) then bolt them on after you're made sure engine compression is perfect, the carbs are tuned perfect, the ignition system is perfect, etc. A poor running motor with N36 manifolds will always get smoked by a good running motor with E88 manifolds.

[2ManyZs]

I agree with John, even though I never heard the myth of the "secret high horse intakes" when I was racing in ITS. Maybe because it was just a lot of BS.

I doubt you could find much difference in the manifolds without doing a sectional cutaway and measuring them with a micrometer to begin with. They are all basically the same design, with very minor modifications during the course of the L series engines.

I also believe that a good port matching does more for an L series motor than anything else you can do in an afternoon in the garage. Although I will say this, I have read that Extrude Honing may not be the best thing on a Z motor as the intakes need some of the roughness to create a disturbance to properly mix the fuel and air mixture. I'm not sure but I think this may have been discussed on the Datsun Garage web-site. I believe it has something to do with the short intake runner length. A slight smoothing of the roughness instead of a polishing is better. (?)

[EricB]

Thanks to the both of you. I am staring at both right now and differences do seem really slight - if at all.....

-e