67L36Driver

Offenhauser made a 'dual port 360' manifold about 20 yrs ago that had separate primary and secondary runners feeding from the carb base to the head ports. At least that's what their adds looked like.

Question is: Did it help mid range torque and improve fuel mixture distribution at part throttle? Anyone use one on a BB?

67L36Driver

TTT

I thought there were enough old geezers on this forum to remember this ancient stuff.

Hitch

It's interesting you mention this as it came up as a topic of discussion tonight. It seems like an interesting setup.. Dave

MikeM

I'm old enough. I have one. It's for a SBC though. I can't answer your question about how they run as I've never done a camparison between it and another manifold. I would doubt there's much if any magic here.

66BlkBB

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

I did a Google search on this one. Came up with two opinions, neither of them were good. Both said that they lost power and performance from their original manifolds. One was on a Big Block Ford and the other on an Oldsmobile. You may want to go to the Hotrodders Bulliten Board (Forum) for a complete answer to your question. They have some real old timers there and have a lot of knowledge about carbs and manifolds. Some of them should have some experience with a BBC with this configuration. I see that you have an L36 also. I went to a Weiand 8013 manifold for mine. It is a clone of the 425 HP manifold but has oval ports. Excellent throttle response and torque is better than the original cast iron unit. I am running a 4776 Holly double pumper on it. Drove to a car show about 140 miles from my home and got 13/14 mpg with it. As long as I can keep my foot out of the throttle an not go over 65 mph while cruising it will get consistent 13/14 mpg. If I go over 65 mileage goes down. Summit Racing sells these. Here is the listing from Summit's catalog.

WND-8013 Weiand Action+Plus Intake Manifolds
Intake Manifold, Action+Plus, Dual Plane, Aluminum, Natural, Square Bore, Chevy, Big Block, Oval Port, Each
Tomorrow $179.95
+ Compare

Hope this helps. Good Luck.

67L36Driver

Thanks for the link.

Presently have a 3883948 '68 passenger intake manifold with an Edlebrock Qjet clone on my 427. I love the driveability but would like a little more economy. That's why I thought of the dual port manifold. Since I have tiny primarys anyway why not have them feed small runners.

Granted, with the divider in there you are going to loose top end. I can live with that if the torque comes up in the 1200-4500 range.

66BlkBB

Isn't your 68 manifold a low rise unit? If so, does it give you as much low end as the original manifold? What does your spread bore give you for mileage now?

67L36Driver

The 3883948 on there is identical to the original 390 hp intake except it takes a spread bore, therefore it is considered to be a "high rise". (Why a Holly style intake and a Qjet intake have the same casting number I can't explain.)

'Old Blue's' original engine was long gone when I got him so I have nothing to compare to. He had a small block, S.O.P. in the late '70s.

True fuel milage is a guess, the speedo has been broken for 28+ yrs. 10 mpg ? Kansas City and back on a tank of gas.

The small block gave me 21 mpg. St. Joseph to south St. Louis county, 309 miles.

gkull

I had a small block Offenhauser 360 manifold mor like 25+ years ago and it was called 360 because the 1/2's of the four barrel were split. Each side only fed 4 cylinders. It was the same as the present day lower RPM dual plane manifold. There is no cut out to alow some flow side to side like the higher rpm rated dual planes.

mr.beachcomber

The Offenhauser 360 was a novel design that seemed to benefit automatic Corvettes with very low gearing (i.e., 3.08 rears) that drag raced. Don't remember anyone ever using one on a manual 4-speed and keeping it. (Even the cast iron four barrels manifolds had better distribution for manual transmissions.)

I'm thinking that you would be better off with the Edelbrock Performer BB manifold is you need a low-rise replacement manifold or the Perfromer RPM if you can fit a high rise manifold under the hood.