How do a set of dual single barrel carburetors on a Fenton or Offenhauser intake compare to a single four barrel carburetor on a Clifford intake? This would be on a Chevy 235 inline 6. Anyone have any experience with these two set ups???
I am running 2 single bbl Carters on a fenton intake on my 230 Plymouth engine. With a milled head, a bit of an opened up exhaust system, and a bit more initial timing it dyno'd at 127 hp at the rear wheels at 3200 RPM. The stock rating at the flywheel was 125 at 3600 at the fly wheel. So I made up for drive line loss. Acceleration, both from stop and from 40 to 70 have noticeably improved. The Mopar flathead 6's had a 2bbl manifold option which increased advertised hp from 125 to 132. I believe I have met that increase or more. Gas mileage is up from 17 to 20 on the highway. Can't compare it to a 4bbl. But seems you would need a very small 4 BBl in order to not drown an other wise stock engine. If you put your engine in a calculator, and figure the efficiency at 80%, at 5000 rpm, it like 298 CFM. Do they make 4bbls that small???
I've got a Rochester 4GC that originally came on an early '60s Buick 215 cubic inch aluminum V8. I've always hung onto it because I figured it would be a good candidate for use on a 235 or similar vintage six.
I have a Clifford and an Edelbrock 4bbl on a 250/th350 in a 48 Chevy. Works great, wish I could put a smaller carb on it, but no disappointments or issues. Will be going the 2 1bbl route on my 55. My dad had duals and 2 carbs and an Offy intake on his 55 (235/stick, stock 6 cyl rear gears, no OD) and it ran really strong. I would think that either set-up would please you performance-wise. I ran cable for my 4 bbl set-up. 4bbl. may make a few more ponies, multi-carbs look better.
To answer your question, you are spreading the fuel air distibution in the intake manifold evenly by using the two carbs as opposed to a single four barrel or the stock carb. The end cylinders are getting the same mix as the center cylinders. Using a 4bbl could load up the four middle cylinders and leave the end ones running leaner.
Actually, on a 235 which has three intake ports, you'd probably end up with the center two running rich and the end four running lean. I agree that dual carbs on an inline six is the best possible setup. Furthermore, both Frank McGurk and California Bill Fisher said in their speed manuals that even on an otherwise stock engine, a dual carb setup will be of more benefit than any other single modification.
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