Cast Intake Manifold dimensions-How Big can you go?

[Xnke]

I have been reading up on Z-ya's SU/EFI manifold marriage, and decided to do some research. Can anyone fill in the gaps on the EFI manifolds, and the other SU-carb manifolds?

 

On the E88 intake manifolds, the carb/TB mounting face opening is 47mm, +/-1mm. LOTS of meat here for porting/port matching. 55mm should be readily attainable.

 

At the cylinder head mounting flange, the runner diameter is 35mm, +/- .5mm. This is a stock cast runner, I can detect no port matching or polishing, just regular casting marks. Parting line and as-cast finish show no modifications.

 

Just before the cylinder head mounting flange, the thinnest measureable cross section I could find on the runner wall was 4mm.

 

Use EXTREME caution when porting/port matching the manifold between cylinders 2&3 and 4&5. The little divider that separates the two runners has thinner walls, probably some 3mm or less.Probably best to weld up this portion if you are gonna be removing more than 2mm from the runner walls.

 

If anyone out there has more information on the N33/N36 carb manifolds, and the EFI manifolds, please post your findings so we can all benefit from the knowledge. Thanks!

[Challenger]

http://forums.hybridz.org/showthread.php?t=134422

 

Heres some info on the turbo intakes. Not sure if thats exactly what you want but... If you want I can get dimensions for the p71, n47, and turbo intakes.

[Daeron]

Z-ya and I had that idea about exactly at the same time.. he made a cryptic remark to a wacky intake manifold idea, and I PM'ed him with a guess right off the hip. I *think* we both may have been inspired by the same comments from TonyD.

 

Unfortunately, I haven't had a chance to play with anything yet, but I have immensely enjoyed his manifold porn

 

I also have access to several stock manifolds, both EFI and SU manifolds but am more familiar with my stock of EFIs... I haven't gotten around to it yet because I am not spending much time up at the family shop, but a thorough inspection of all the differences in the manifolds I have is on my "to-do" list, largely for just this purpose.

 

I am mentally busying myself (have been all day) throwing ideas around for a plenum/divider of sorts for this setup, and pondering all day what could be done to improve everything, and where... My impression is that it shouldn't be very difficult to build a rather compact plenum box that would evenly and equally distribute things into the throttle bodies, and then to work some more on the manifold itself to get it ideal. I may end up cutting a set in half along the horizontal plane and do some serious re-working, basically using the manifold as stock........

 

 

...but thats all ideas batted around thus far. I won't see fruition on any of this for a long time, so I hate to talk about my ideas out in the open lest someone else build my car before I get to.

[Xnke]

Guys, the dimensions I am looking for are pretty much what I gave for the E88...Carb/TB mounting orifice, porting/port matching potential, runner size, and runner wall thickness. Also, any consistant thin spots or pitfalls.

 

A pair of calipers and about 20 minutes is all it takes, so if anyone here has access to the common or uncommon types of stock manifolds, by all means help add to the wealth of knowledge that is HybridZ.

 

For example, I've read on here from reliable sources that the runner ID on the N47 intake are 30-32mm ID, with not much room to port or port match. I'd like it if someone could actually measure and confirm or deny that this is true. Especially the N36 carb intake manifold...the 10Hp claim has some meat to it, but why? are the runners different? bigger ID? longer?

[z-ya]

For example, I've read on here from reliable sources that the runner ID on the N47 intake are 30-32mm ID, with not much room to port or port match. I'd like it if someone could actually measure and confirm or deny that this is true. Especially the N36 carb intake manifold...the 10Hp claim has some meat to it, but why? are the runners different? bigger ID? longer?

 

Isn't the wall thickness most important when porting the intake? It is not so important what the port size is now, but how much material can you remove without effecting the strength of the manifold.

 

What are you trying o accomplish? Do you want to put together a spreadsheet that shows all port sizes, wall thicknesses, etc for all L6 manifolds? Or, do you have some project in mind?

 

In the case of port matching EFI manifolds to the stock port size on N and P series heads, there is plenty of material. I have done this on N42, Turbo, and a 280ZX NA manifold. So unless you are going to enlarge the stock head intake port size dramatically, all EFI manifolds can be port matched.

 

For my SU/EFI project, I have been able to port match it to a stock manifold gasket without the wall thickness getting too thin where the two manifolds were grafted together. This manifold will be used on either my race car and dyno tuned in August, or on the 3.1L I'm building for my 71' project.

[blue72]

I have very similar findings from an N-36 manifold:

Carb/TB mounting face diameter: 47mm +/-

Cylinder head face runner diameters: Average of 35.8mm

(disclaimer: I already gasket matched this side of the intakes to my Ported and Polished P-79, but not much material was removed.)

Thinnest spot I could reasonably measure: 2.9mm +/-

 

I picked them up because of the rumor, but now it appears unfounded. BTW they came from a '73 240Z with the square top SU carbs.

[Daeron]

One of the primary differences in the various SU manifolds is the shape and aspects of the walls that divide the single channel first into two, then one of those channels dividing into two more.

 

The shapes inside of the manifold are slightly different. My point is, the "10 hp" claim is based on more than sheer size.

 

Trust me, when I get to it, I will add a TON of data to this post. I want to do the same thing you are doing, and I have about 12 EFI manifolds and i dont even know how many SU manifolds (at least 3 or 4 i can easily get my hands on, likely FAR more.)

[z-ya]

I guess my point is that it doesn't really matter which EFI or SU manifold you use (especially EFI). You will need to do a lot of porting and smoothing to open up the SU part of the manifold for the 50mm TB, and where the two manifolds are welded together. Then add port matching at the head.

 

Pete

[Xnke]

Not as much opening up as you think. I can fit the E88 intakes on my lathe's faceplate and open up the carb mounting face to 50mm easily. LOTS of meat on this casting.

 

VERY interesting numbers on that N-36 manifold, I guessed as much regarding the internal division.

 

Yes, the eventual goal was to build up a spreadsheet or listing of all the manifold castings and the characteristics of each, for reference. I am generally trying to eliminate a lot of the "this manifold, that manifold" crap that I see on the web, and nail down the good and bad characteristics of each. To start out, i planned to make a chart of runner diameter, length, and wall thickness, but haven't figured out a good method of measuring runner length on my carb manifolds. (don't have any EFI manifolds here.)

[Daeron]

What about using dual-bore throttle bodies on each SU manifold?

 

http://forums.hybridz.org/showthread.php?t=135192

 

I am thinking....

[blue72]

I get my overbored SU's back from Rebello sometime early next week, so I'll probably be enlarging the bore on the "meaty" side. I also have in my collection a set of E-88 and E-46 SU manifolds that I can measure as well. It'd be best if we could come up with a standard system to better differentiate the variations between the iterations. I'll probably have them all side by side in about a week and give the results from my untrained eyeball if I find anything interesting.

[blue72]

It took a little while to get my cabs back, but I did and now they're on. I went ahead and dug out my stash of SU carb manifolds and thought I'd give the numbers I have for each. I took the averages from both manifolds in the set.

 

N-36

Carb/TB mounting face average: 47.2mm

Cylinder head side average: 35.83mm

(previous disclaimer: I already gasket matched this side of the intakes.)

Thinnest spot I could reasonably measure: 2.9mm +/-

 

E-88

Carb/TB Mounting face average: 47.08mm

Cylinder head side average: 34.78

Thinnest measureable spot: 3.7mm +/-

 

E-46

Carb/TB Mounting face average: 47.92mm

Cylinder head side average: 34.61mm

Thinnest measureable spot: 3.4mm +/-

 

Nothing real groundbreaking there. They are pretty close to each other, so on port size alone there's not much difference. The greater differences that I noticed were in the port shapes and lengths of the manifolds themselves. The E-88 was overall 14.3cm, the E-46 is 14.2cm, but the N-36 manifold looked to be half an inch shorter. I didn't measure it because I was too excited to put it on.

 

Left to right: E-46, E-88, N-36

 

As far as inside the manifolds there seemed to be two main differences between each variety. Both the E-88 and E-46 manifolds have a sharp radius on the 2-3/4-5 side. The casting sticks out into the passage and forms a sharp lump inside. Also, where the two divide into individual runners is a sharp line.

 

I'll try illustrating with a few pictures:

First the E-88

Next the N-36

 

On the N-36 manifolds the bump is significantly smaller on the 2-3/4-5 side, and forms a nice smooth radius. Where the 2-3/4-5 sides divide into individual runners is also a much smoother radius, and shorter as well.

To my untrained eye the #1 and #6 cylinder runners looked identical between all manifolds.

 

Hope this helps someone. Its info I'd like to have had in the past.

[Xnke]

Now that's something to know. Looks like then N-36 manifold has a straighter shot into those particular runners, than the two E-series manifolds. I wonder if the N-33 intake is similar?

[Daeron]

BLUE, thank you, and what wonderful timing. I was looking at a flat top set of carbs with manifold earlier this afternoon, and should be back at the shop within the next week... I THINK it was an N-33 but it may have been a 36, and theres the nonzero chance i'm mixing the numbers up entirely but it was a flat top manifold.. the carbs were still on it. Anyhow, there was that and others handy; the race car engine is being rebuilt so its nice pretty manifold is off, I should be able to get some good shots.

 

If I make it up there I will review this thread first, get the measurements requested, and get anything beyond what we already have here that I have handy.

[MrZ]

Wow, those are nice info. I still have an extra E88 lying around.