Technical Offenhauser 2x4 348

I have A348 Chevrolet engine with 3 deuces I want to upgrade to an offenhauser 2x4 intake I have a very mild Cam and 11 to 1 compression pistons the heads are factory 379 I'm wondering what would be a good choice for CFM's on square bore carburetors

 

I’d use 2 Carter WCFB’s like 245 and 270 SBC’s from 56-61. Depending on the manifold run them progressive; Folks say they are about 350-375 cfm and 1 is stock to a 348. They are still somewhat reasonable, traditional, and look good under 1 or 2 air cleaners. Millions of Chevrolet’s ran them and linkage is a breeze. I run 2 Carter WCFB’s on a non traditional engine and have for 6 years.

 

Not sure that manifold is a upgrade. Poor designed out of the box.

 

Steve, check with the boys and classifieds over on the 348-409 site. Might find those carbs there.

 

I did a 348 with 2X4's several years ago and used the Edelbrock 500 CFM carbs designed for a 2X4 installation. It did have the look.

 

Yeah, good luck. 400cfm (properly working) Carters WILL cost you...big time.

While it won't "look" factory, Holley makes a 450cfm carburetor that will be workable.
Or you can go with the 500cfm Edelbrock. These will at least look a little more "factory".
They have the new AVS2 carb. It's setup so you can manually adjust the secondary side. So if the 500cfm is too much, you can make the secondaries open later or not at all for better full throttle power.
The primary side is already pretty restrictive.

- With the AVS 2, you should not have an over carburetion problem.
-With the Holley 450's, it's also adjustable with different secondary springs. Again, these should be able to make work well on a 348.

Mike

 

With no disrespect meant to anyone, Carter 3361s (front) and 3362s (rear) (factory 409 2x4 carbs) were actually rated 625 CFM each. The superseding 3804s (rear) was also rated 625 CFM.

A pair of Carter 500's should work very well on a 348.

Suggestions, depending on state of tune of the engine:

Basically street - (2) 9500s or 9510s (may mix or match) (these are 500's)
Performance street - (2) 4758s (these are 500's)
Trailered race car - (2) 4759s (these are 625's)

EDIT: there is also a comment about the Offy being a poor design. I do not know as have not tested these on any Chevrolet engines. On Pontiac V-8's the Offys are significantly better than the Edelbrocks, but not as good as original Pontiac designs (just a lot cheaper ).

Jon

 

What’s the reason for wanting to go away from the tripower? Have a tripower setup on my 409 with small port heads and she pulls hard with great throttle response.



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3 x 2 only equals 6. But 2 x 4 equals 8. ?

 

Tri-power is one of the old standards of a hot rod! Another more rare icon is four deuces! A Man-A-Fre or Offy4x2. 348 Chevy.
SBC Offy4x2
BBC Man-A-Fre with the ultimate afterburner accessory, “The Sting Of The Honey Bee”.