Slick 60's

Ladies and Gents,

I ended up with an Offenhauser 360 intake manifold for next to nothing and figured it has to be better than the old cast stock unit.

Anyone have any first hand experience with the old School offenhausers?

I have a holley Next gen 600 and a mild cam, just looking for a little more umpf..

Is it a Dual Port for FE? I have not owned that model but would like to have one and run the carburetor backwards so the primaries are flowing from the top. I mocked up a 6 cylinder accelerator cable and it looked long enough to work.

It is for the 289 in my truck. Appears to be a single plane.

RRTEC wrote:It is for the 289 in my truck. Appears to be a single plane.

My FE Port-O-Sonic 360 had no divider. An engine typically looses 1-2" of vacuum and low end swapping from dual to single plain but gains higher up top.

The typical Offenhauser divider splits right and left bank and is a dual plane or 180. The notch in the divider balances a dual plane for some performance, in your case maybe Offenhauser notched a 180 cast to make it a 360?

A true 180* intake looks like a factory intake. There are two plenums and alternate firing cylinders (1-5-4-2-6-3-7-8) draw from the same plenum. In other words cylinders that fire next to each other draw from different plenums.
The true 180* design tends to work better at lower rpm's that a common plenum (360*) with all cylinders pulling from it. At higher rpm's the common plenum tends to produce more power.

The Offenhauser 360* intakes tried to have the best of both worlds with their own design. The intake pictured was not a 180* nor was it a true 360*. Cylinders 7 & 8 drew from the left plenum and cylinders 4 & 2 drew from the right (1-5-4-2-6-3-7-8).
If you believe the street racers of 50 years ago, the idea didn't pan out. The faster cars usually ran Edelbrock or Weiand, not Offenhauser.

The notch on the plenum was for throttle plate clearance. In the late 1960's Holley offered a 3 barrel carb rated at 950 cfm. It looked like a regular 4 barrel unit until you turned it over, There were the two primary throttles but the secondary was a very large oval with flat sides. Think of the shape of the Indianapolis race track. Without the notch the secondary couldn't open. Edelbrock offered manifolds for this carb also. The standard Edelbrock sbc "hi-rise" was the C4B (Chev 4 barrel), the 3 barrel version was the C3B.

The DP (dual port) 360 took a different approach. It came out at the beginning of the factory smog motors. It tried to put some performance back into the low compression low horsepower engines.
Each port runner was divided, about 40-60, with the smaller part being primary and the larger being secondary. The basic thought was that by keeping port velocities higher by using a smaller port, the fuel would stay atomized better and lead to better combustion, creating more power.
This seemed to work OK on smaller engines but not so well on V8's. I ran one on a 2.0 liter Pinto with the factory Weber 2v carb. This carb had a primary and a secondary barrel and for all purposes was half of a 4 barrel carb. The intake was great. Better power and mileage.
I also put on a '72 Ford with a 429. I had installed the straight up timing set as well. After a week I put the factory intake and carb back on the rig. Nuff said about my experiences using the DP 360 on a V8.

Thanks for allowing an old fart to ramble and reminisce.

Roger Carter wrote: Thanks for allowing an old fart to ramble and reminisce.

Thanks for taking the time to do it. Keeps the rest of us from guessing. I was told that FE Offenhauser 180° was divided right and left bank down the middle. Is that incorrect?
Thanks
PM'd you on the Dual Port.

chris401 wrote:

Roger Carter wrote: Thanks for allowing an old fart to ramble and reminisce.

Thanks for taking the time to do it. Keeps the rest of us from guessing. I was told that FE Offenhauser 180° was divided right and left bank down the middle. Is that incorrect?
Thanks
PM'd you on the Dual Port.

I don't remember Offy offering a 180* intake for an FE. If their FE (or any modern V8) intake had a divider down the middle it wasn't a true 180* intake.

PM answered.

I am more confused than ever. I blasted it.. cleaned it, and painted it. I feel like I know less about what I think I have than before......

What does it look like underneath?

I found an old Jay Brown post on the FE Forum with the same split port info I was told but a 360° not a 180°. As Roger said on the notch it clears the Holley 3v carb but I have seen it custom cut also in dual planes for ballance. In Offenhauser design it seems to have a dual purpose.


http://www.network54.com/Forum/74182/th ... s+thing---

Roger,
You did a nice job of cleaning that manifold up!

Since you got a good deal and have it all cleaned up looking nice, I'd simply run it. I'm sure it'll be better than your OEM intake and work well with your 600 Holley and mild camshaft profile.

What transmission do you plan to use?
What rear end gear ratio will you use?

BarnieTrk

I had both the dual plane and 360 manifolds on my 65. I liked the 360 better as the linkage for the carb was easier to hook up. I ran and edelbrock 500 on my 300 CI. It ran well. I also had headers and duals.