View Full Version : Offenhauser 2x4 Intake w/Carter Carbs

OE Espo
April 24th, 2009, 13:38
Does anyone have an interest in some 1968 GTO parts?: Intake PN#ending 140, Heads Casting #15's, 8-Track Player? I have a lead on some parts and the seller wants to sell as a package.

He has an Offy 2x4 with matching Carter AFB's that I am interested in.

Does anyone out there have any opinions on the Offy 2x4 Setup?? I was thinking about installing it on either my 66 Lemans Auto or 68 Bird 4-spd. Both have 400 cuin in them. If you talk to my wife i probably dont need any of it.......

April 25th, 2009, 05:57
Having personal experience with these setups I would highly recommend it. What I can't do is tell you how to convince your wife that you 'need' the thing.
I used dual Carters on an Offie '360' intake which is single plane unit. I set the carbs up to be progressive - run on the rear carb and progress into the front carb - feels like infinite throttle. This was on a 455 engine in a '61 Bonneville with a 200-4R auto O/D trans. It ran great! Cruising at 70 on the highway it got as much as 18mpg.
I also set up a similar combination for a friend in a '68 Firebird with a 350 cu in engine and 4 speed. It also performs very well and it sure does look good when you open the hood. That setup was a bit more complicated due to the throttle cable and had to do some fancy fabricating to get that to operate properly, so be aware of that aspect. Because of the closeness of the rear carb to the firewall, the throttle cable mounting bracket had to be modified and mounted on the intake further to the rear and put the cable in a fairly severe bend. Too difficult to explain in words here, but I got it worked out and the car runs great. The carbs on this setup are the Edelbrock version of the Carter AFBs.
Good luck with convincing the wife and have fun with the car(s).

Mike Nixon
April 25th, 2009, 20:21
I've got a New 29 yr old set of of this that'll probably go on my 68 GTO when I do a serious engine for it.


OE Espo
April 29th, 2009, 15:40
Thanks for lending me you experience of this setup.

May 31st, 2009, 06:56
In 1980 I built a 400 for my '68 Firebird convertible. I used the 360 degree Offy with 2 AFB's, they were 500 cfm units. I got it working fairly easily and it idled and transitioned from rear to front smoothly. However it ran 13.0's on the 2 x 4's and 12.70's with Edelbrock 180 and a single 780 Holley, so I sold it.;)

Mick Batson
June 11th, 2009, 16:04
I ran the Offy manifold with Old 650 AFB's and it was a trouble free setup. I had Edelbrock 87cc aluminum heads, Comp HR288 cam, and Doug's headers to round out the package. Even with this setup fuel economy on trips to shows 80 to 100 miles away always netted right at 15.9 MPG for the round trip, and this is in SoCal freeway traffic. I sold the shortblock to one of our club members, so the manifold and carbs are sitting on the shelf waiting for a new project.

Only short side was even with the ported heads and plenty of carb size, this manifold was done by 5,200 RPM on the dyno. Although the manifold was port matched, we figure that the very low profile design of the Offy runners killed the upper RPM range. The low and midrange of the setup was extremely responsive and perfect for the street.

Les Iden
November 22nd, 2009, 19:53
I have run dual AFBs on an Offy low rise intake on my 68 GP for the past three years w/ great success. Details on request......


November 23rd, 2009, 19:53
I'm running that same set up, w/carters, re jeted down to the smallest I could get. Works well on the street, can squeeze 17mpg on the highway [2:67 gears] & still spin the tires in 2nd. with turbo 350 trans. Rev limiter in crane dist. conversion is set at 5500rpm. & engine is peaked at that rpm. trouble free in last 7 yrs.