N36 Manifold Experiment

[ChrisA]

Okay guys, I've decided to give in to the myth about the 260Z N36 manifolds being better than the E46's. My 240Z has been punched oversize. Not sure how much as previous owner couldnt remember. Car has a stage 1 cam and ZT carbs. I've never had it on a dyno but it definitely is stronger than a bone stock 73 Z as I have one of those as well. I have upgraded the ignition also.

So I bought a set of N36 manifolds on eBay and decided, what the heck, I'll be my own guinea pig. I made a jig to mount the manifolds and I'm doing some mild porting to get rid of the parting line roughness. Its amazing how rough they actually are.

I've read as much on the subject as I want and I know some will say the manifolds need a little roughness to keep the fuel in suspension. Okay has anybody looked in a new Edelbrock V8 aluminum intake lately? Amazingly smooth. All the way from carb flange to head flange. So what I'm doing should give me something. Remains to be seen whether its good or bad. If its bad, I'll just put the stockers back on and no harm done.

Any advice either way will be appreciated.

Chris

[xray]

Good luck Chris!

I've been looking for a set of N36s, too...guess you beat me to them.

Look forward to seeing the end results (with dyno proof) to confirm/deny the myth!

Steve

[jmortensen]

I believe Matman has a few N36 manifolds. You might try PM'ing him if you're still looking.

[beandip]

Okay

I've read as much on the subject as I want and I know some will say the manifolds need a little roughness to keep the fuel in suspension. Okay has anybody looked in a new Edelbrock V8 aluminum intake lately? Amazingly smooth. All the way from carb flange to head flange. So what I'm doing ny advice either way will be appreciated. should give me something. Remains to be seen whether its good or bad. If its bad, I'll just put the stockers back on and no harm done.

Chris

Well , for one thing as soon as you modify the #36 manifold any numbers you get testing on a dyno will mean nothing . If you want to test for effectiveness . First run the stock manifold then the 36 unaltered then do all the grinding you want and test again. The numbers will then show the differences. Comparing a large V-8 to these little 6s is comparing apples to watermelons . Every engine builder for performance that I have talked with about these in line engines has said just what you alluded to . The roughness in the intake is left for a purpose , to cause turbulence and to keep the fuel mixture from condensing on the walls of the manifold . Smoothing out the exhaust manifold is a different matter . Now matching the size of the intake and exhaust ports to the openings on the head and sizing the gasket also should be done . This information that a 10 HP gain has been kicked around for years and years . I have never seen or heard of anyone actually proving this on a dyno . Seat of the pants results mean nothing to me . Phred who is a member here may have some input on this as he builds these engines . Kim Blough is another . Gary

[montoya_fan01]

Good Luck Chris, Let us know how it turns out for you

[dspillman]

Hi Steve,

If having problems finding the N-36 manifolds, give a N33 a gander....came on the 73 240Zs, other then the number cast, on top, look identical. From memory the casting number on bottom side is the same as well.

Chris,

Testing the polished intakes could distort results somewhat. If interested, I'd be happy to send you a untouched N-36/33 to test along side your other intakes...

david

Good luck Chris!

I've been looking for a set of N36s, too...guess you beat me to them.

Look forward to seeing the end results (with dyno proof) to confirm/deny the myth!

Steve

[jmortensen]

This information that a 10 HP gain has been kicked around for years and years . I have never seen or heard of anyone actually proving this on a dyno . Seat of the pants results mean nothing to me . Phred who is a member here may have some input on this as he builds these engines . Kim Blough is another .

This subject came up on Hybrid Z and Keith Thomas and Norm the 12 second SU dude both chimed in supporting the N36 manifold as an upgrade to the earlier manifold. Norm said that you get more even fuel distribution and you could tell just by looking at the plugs.

[bjhines]

There is a definite pattern to plugs in a fresh engine run on track for 30 minutes at a time...SUs and any factory manifold have poor distribution... but the N36s are better.... I am now running triple weber DCOE 45s on a TWM manifold...

with a cold air intake box quieting the Webers.. the engine has a totally different exhaust note... same cam, same engine..

Equal length intake runners make the whole thing smoother... It sounds more like a European sports car...

and I brought up power in the mid range as well as top end.

[ChrisA]

Hello all,

Thanks for the feedback so far.

Tonight I removed everything from the head. I decided to do a trial fit and make sure everything would go smoothly. So far so good. Carbs/linkage/balance tube all fit the N36 manifolds like they were meant to be there.

I thought I had a pretty tidy engine bay till I got all the stuff off. A good cleaning is in order after its back together.

I took David's (dspillman) advice and will dyno a set that I did NO porting on and then will dyno the ported set. Three dyno runs ought to prove one way or the other.

I've attached some more pics. I shot a close up of the butterfly on my ZT carbs I got in 1998.

Chris

[zeiss150]

sooooooooo.... What happened? More HP? Or is it just lame BS?

[ChrisA]

Well, the tweaked N36's are on the car. I've driven it on the street three times. Seat of the pants (which means nothing to some) reaction is that there is no difference till 2500 to 3000 RPM. Then the motor seems to come to life. There is no dyno that I can find in Lincoln. I have to go to Omaha. And right now, I'm still getting the bone stock set of N36's ready so I can do a stock versus tweaked comparison. It'll happen though, eventually.

Car is not going anywhere right now as I'm replacing the rear struts.

Anyway, if your motor is bone stock, this modification will do nothing for you. Mine is not stock.

Chris A.