I picked up a decent looking polished Offy "Dual Port 360 Degree" intake manifold to go on a 440, but I'm a little skeptical about the port design. These are crazy intakes where the planes are split in the intake runners.

I included a picture of the ports, wouldn't the squared off design hinder airflow? I was thinking I should grind a taper into these so the shape is more like an airplane wing and that doing such a modification would likely increase velocity into the cylinder head.

What do you guys think? It's a mostly stock 1973 standard 440 that will get headers and a low end torque grind cam.

I think that it is too light for a boat anchor unless you have a real small boat.

I ran that intake with a thermoquad and a very low compression 440. The bottom end was very good. But that was like 25-27 years ago.

Some users of that intake used to take about an inch of the divider out to gain more top end.

It's an interesting piece to try.

Certainly not the best intake out of the box, but this intake isn't as bad as you guys think...

Only 7 ft-lbs less torque at peak than a Mopar M1 single plane, but about 40 less horsepower at 6000 RPM, which makes a lot of sense since there's a giant chunk of aluminum in the runners...

Hot Rod Mag did dyno test it and a bunch of others:

http://www.hotrod.com/techarticles/hrdp_0712_mopar_intake_manifold_comparo/offenhauser.html

So jokes aside, I'm trying to figure out a way to make this intake a little better....

Here is what I'm talking about, Willis:

By reshaping the divider as it leaves the intake I believe I can aleviate some of the problems associated with this intake.



The air will come out faster than having the squared off edge, as the squared off edge will increase turbulence and create drag slowing down the air going into the cylinder head.



Sound theory worth experimenting with?

Like I said, this is for a stump puller, not a high RPM drag engine, and I only paid $40 for it, because it was kinda purdy-like...

I had one on my beater '69 300 many years ago.

It did pick up the part throttle torque and response noticeably. The tiny runners for the primaries do work.

At WOT, I always felt the stock manifold was actually a little better, though.

This was a decade or more before I got into dynos and dragstrips so all I've got is seat of the pants info. Trying to judge by feel, that's all I've got for ya.

FORTY hoes-power LOSS at 6,000 rpms .....

There was a topic some-time-ago mentioning this manifold ...way-back-when ...when this was available BRAND NEW ... they were BIG BUX. IIRC .... something like 450$ ...???

I bought one of these at a swap meet at Milan some years back for a huN .... just because it was so uNique.

It HAD to have been a horror show making the sand-mold for the casting operation THEN even worse getting all the molten aluminum into all the small spaces.

TO ADD .... if you wind-up not using this ...I will buy it from you EVEN just as a paper-weight ...

So, in everyone's opinion, nothing will be lost by reshaping the ends of the runner divider? Can't possibly hurt the flow anymore, huh?

rs ..... IF all you are really just concerned with running on the primaries ... it is a decent intake ...as I said before and also OTHERS have mentioned.

But just LOOK UP into the manifold ... it has got to be one of the more restrictive aftermarket intakes ever made.

I do not know what OFFY was thinking. It might have been made to compete with the Eddy Streetmaster or SP2P .... ???? I was not screwing around with that type of the "MPG" stuff back then.

What are you trying to put together ?

Offenhauser was the dominant manifold company in the 50s and 60s. Because of that I think they tried to be "creative." If that Dual Port design would have been legit I have to believe Edelbrock, Weiand and Holley would have made a knock off of it. To the contrary- Offenhausers best manifold- the Port O Sonic looks like a Holley Strip Dominator, Weaind Team G and Edelbrock Victor. Im thinking Offenhausers outdated single plane manifolds were poor compared to the other single planes with swept runner design so Offy decided to make the sonic. BTW- Offenhauser NEVER made a true dual plane manifold. All there units were a big open single plenum/cavern.