which intake manifold has bigger runners?

[z_boi]

Ok. Im in the prosess of port matchin my intake manifold and was lookin at the runner inner diameters on my 280z's manifold. My friend has a 83 280zx and we've had his intake off b4. He compared it to a different manifold (not sure wat car it came from, maybe a maxima?) and his manifold had larger runners. Im not exactly sure of it but i tink it does. So i compared mine to the other manifold and it was the same size.

 

So my question is basicly, does the 280zx intake manifold have larger bore runners than the one on my 77 280z?

 

And another question is, does anyone know if it would be better to use the 280zx manifold because it has a different design? which design is better?

[Drax240z]

Well I can varify for sure that the turbo runners are not any larger than the NA runners, a myth that I have heard quite a few times. I measured them both and they are the same.

 

As for what is the best of them, I like the 75-76 non-EGR manifolds since they start out cleaner than the others. As far as flow goes, I suspect you'll find very little difference between stock manifolds.

[clarkspeed]

Grab a 75 and simply port out the casting tits that protrude into the outlet bores so the inside is round. Also port the inlet to fit a bigger TB. Flows pretty good then!

[Guest smoov280zx]

ROFL. "casting tits"

[fl327]

ROFL. "casting tits"

[z_boi]

i jus decided to go ahead and use my original manifold. i have a block off plate on the egr and i am using a 60mm tb. i was port matching today and took off a little too much. now theres a small hole. its ok. i put some jb weld on it and im goin to smooth it all out when it dries. its on the bottom side so u cant see it.

 

Whats a good was to polish the inside of the runners. to smooth it out? slightly port n polish it.

[spacecase70]

have it extrude honed

[BRAAP]

This thread fired me up to spend this afternoon measuring a few EFI intakes that we have laying around the shop and posting those results. Mind, you I only measured 4 manifolds. 2 of them are Turbo intakes, the other two are N/A. One of the N/A is a non EGR P-82 off a friends 280-ZX, the other is a NON EGR N-42 intake manifold. I have no idea what years the Turbo intakes are, sorry. I’m sure measuring all the EFI intakes that Nissan used would be more accurate, but I strongly feel the results I acquired and posted here are good enough for the intent of this thread, i.e. I don’t think measuring them ALL will reveal anything not found here.

Also, keep in mind, these are cast parts, and as such, there are some pretty drastic differences between manifolds, let alone within each runner due to the casting molds etc. I started out also measuring the runners horizontally as well as vertically, but the casting part line was skewing the measurements so much, and being as the runners are, for the most part round not oval, I just used my vertical measurements.

 

There have been strong claims made both ways as to whether the Turbo intake manifolds have larger diameter runners as compared to the N/A manifolds, (I have taken part in those discussions myself).

 

In summation, yes the Turbo manifold has ever so slightly larger runners, and in defense of DRAX, that difference is NOT worth any effort to replace any other existing OE EFI intake that you may be already using. (I take back all the statements that I made previously in other threads in regards to the Turbo intake manifolds being a worthwhile upgrade). ALL of the OE EFI manifolds are RESTRICTIVE, PERIOD! No real gain in power will be had using one over the other. There are much bigger performance gains to be had in just dialing in your ignition timing and Air Fuel ratios than switching to a Turbo Intake manifold. Best case, the Turbo intake runner has only 6% more cross sectional area in the ports than the N-42. 6% cross sectional area in the port runners is a small increase in cross sectional area, but it isn’t going to show squat in power or ¼ mile times on a stock engine, and on a radical engine, boosted or N/A, if you are using ANY of the OE intake manifold’s, you are just shooting yourself in the foot. NONE of the OE EFI intakes will allow any of your other power producing parts an/or modifications to perform anywhere near their optimum. If a real marked performance gain is your goal, make sure that none of the OE EFI manifolds are on your engine. They can be made to look real nice and will perform respectably, but more power can and will be had by switching to an aftermarket manifold with larger than stock diameter runners.

Extrude hone was mentioned. I would agree that if the runner could be safely opened another .100” using that process, that would help. Realistically, opening it up another .200” would make it worth while, but I’m not sure there is enough material in the runners to safely remove that much using the extrude hone process. Also, the cost of extrude hone for a little gain is something that you’ll have to weigh against your bank account. For some, it might be more cost effective to spend a little more for a custom intake which would allow the rest of your performance parts and modification to do their job to the fullest, not just partially.

 

 

Here are the details of this afternoons measuring session on these manifold runners.

 

I measured all 6 runners of all 4 manifolds and I measured each and every runner in 3 different locations along the length of the runner. I was using my machinist snap gauges and Mitutoyo 0-12” dial caliper. First measurement point “A”, is 4 ½” from the head flange. Point “B” is 2 ½” from the head flange. Point “C” is at the head flange, ¼” in from the flange surface.

 

 

Top pic shows the manifolds that were measured.

 

Second pic shows the locations at which the measurements were taken, “A” “B” and “C” respectively.

 

Third pic is each and every measurement taken at all three points in all runners of all 4 manifolds, to within .005”. Average runner diameters per location, avg per individual runner, and avg overall. At the bottom is the square area of the averages and the % of difference between the two N/A vs the Turbos, (I used 1.308” Sq/in for the Turbo Reference).

 

 

 

[SHADY280]

so, what size is good for a runner?? is there calcualtions per each application? or just do it to the size of your heads port size? its quite the science to build such a manifold, but what are some realistic tips and advice? so many questions, so many opinions

[BRAAP]

If you haven’t seen this project already, this should help shed some light on L-series port sizes.

 

http://forums.hybridz.org/showthread.php?t=117607

[SHADY280]

stopped following it a ways back, had the drg files sent to me a while back. prolly should keep up on it. thanks for the link, i always forget about that section.

[e_racer1999]

was admiring that manifold yesterday..... NICE

[Daeron]

BRAAP: just a totally off topic PC note:

 

Instead of taking a photograph of your screen to simply capture part of the display as an image, you can hit "print screen" which copies the entire screen to a bitmap image on the clipboard. Then enter paint or any other graphic program, and paste it into a new file, cut and paste the section you want, save it as a jpg, and bingo.. no need to deal with silly lines across the screen from a photo

[Zmanco]

Just to add a little more to what BRAAP suggested, Alt-PrtScn (pressing the alt key and then print-screen key) will copy just the active application's window instead of the whole screen. If that's all you want to share, then there's no need to edit any further.

[BRAAP]

Thanks for the tip guys. That defiantly would help in clarity for sure.

For some reason I have this terrible habit of using the camera.

[Daeron]

eh, six of one, half a dozen of the other. "print screen" involves fewer steps and is simpler IMO. hope it helps.