I have a question about intake manifolds, I was just thinking for a winter project. I have a stock 280zx motor with a header and 4 bolt su carbs. so right now, I have the e46 intake manifold on the motor and the car runs great. but I heard some place years ago that the n36 has better flow. has anybody made the swap, is it worth the hassle. and if so, do I use the 71 carb thick insulator or the 260z thin insulator from the n36 intake. thanks again kully

Edited December 9, 20231 yr by kully 560

I haven't tested any of the manifolds, but I'll go out on a limb and say that you will not notice any difference at all. And if there is some minuscule difference, you would only be able to pick it up on a well tuned dyno with multiple runs. 

That said, I've heard the same thing about the N36 manifolds. And if I've heard it and you've heard it, then probably lots of other people have heard it too. The point of that is... If you switch to the N36's, you would be able to say things like:

"Lots of people say the N36's flow the best of all the intake manifolds, right? That's why I put them on my car."

So, I'm clearly not providing any technical expertise on flow characteristics, but I CAN tell you that you would use the same thick phenolic spacers you are currently running with your E36 intakes.

I can also warn you about one potential pitfall... If you are running coolant through your E36's now, you will have a problem with the N36's because they have a hole on the face where the carbs mount that will leak of you run round tops there. I suspect you are not running any coolant through your intakes currently, but thought I would bring it up just in case.

thank captain, I do run the coolant and never thought about the leak from the n36. may just leave well enough alone than!

Actually thinking about it a little more, I think you could put your round tops on the N36 without a coolant leak. There were coolant holes in the previous intake manifolds for the 3-screw round tops in 72, but they gave up on that idea and ran coolant direct into the carbs starting in 73. I don't think there are holes in the carb mounting face of the N36 manifolds. There are "teats on a boar" holes in the back side of the carbs, but no matching holes on the manifold side.

So you're back to being able to say that you have the best flowing intake manifolds installed. If I had the manifolds off for some other reason, I'd put the N36's on just because. Not sure if I'd go through the trouble just to switch, but if you had it apart for other work as well. 

Supposedly, the N36 intake has up to 10% more air flow than the E46 intake (can measure the opening to the carbs and see the difference).  Like CO says, not sure how much upside there is to using them, but I have read the same positive take on using them.  I have the N36 on my Z.

22 hours ago, Duffman said:

Supposedly, the N36 intake has up to 10% more air flow than the E46 intake (can measure the opening to the carbs and see the difference).  Like CO says, not sure how much upside there is to using them, but I have read the same positive take on using them.  I have the N36 on my Z.

"Supposedly up to 10% more."

Perfect. 

So I'm not sure about the openings where the carbs mount. I haven't measured them to compare, but I do know that the carb throats themselves are the same between round tops and flat tops. They are all 46mm, so it seems like all the intake manifolds would have that same hole in them. I've got both varieties of intakes around here somewhere, but it will probably take me some time to find them and measure.

I was thinking about doing this and when the intake and exhaust manifolds were off I would like to repaint the engine block. kill 2 birds with 1 stone, and like I said just a winter project. 

I like it! Sounds like a good winter project!

Hope the project goes well with no surprised.

thanks, I let you know how I make out. should be a fun project kully

I to have “heard” for many years of the increased flow of the n36 “260z” and the n33 “73-240z”  intakes.    It’s quite visually obvious looking into the carb side that there is a straighter path for a couple of cylinders.

     If I remember correctly you can swap the longer carb mounting studs from the n46 onto the n33/36 and retain the thicker isolater.   
 

David

thanks for the reply, I do know about the longer studs that need to be used. I did read years ago that the plugs did burn more evenly also.