Inliners International Forums General Discussion Bench racing Rochester airflow

Does anybody know the CFM rating on a Rochester M single barrel carb?

I've seen the ratings, but don't remember the exact figures. These should be in the neighborhood, 230 cfm for Model B, 240 for the Monojet, and 275 for the Holley/Weber 2 barrel.
Larry

Just to rehash this, is the HW 5200 a good replacement for the stock monojet? I ordered one from stovebolt today he mentioned its not enough to feed the 250 but in stock form shouldent it be fine?

The new one you ordered is a progressive two barrel, it runs on the front primary till you open it up, then the second barrel opens, so no it won't be enough for a 250 unless you drive around wide open all the time. This is why they work so go on dual carb manifolds. Joe

Well this is just to get the car on the road and crusiing around. Not looking to make a seed demon out of it. Eventually I will stick a 4bbl on it or a holley 2bll

I still say no, you will be running on half of that 275 cfm most of the time. It could be less then half depending on how the carb is designed. Think of a quadra-jet four barrel, they are rated 750 cfm, but the front primaries are in the 200 to 300 cfm range, the remaining cfm comes in or by kicking it to the floor! Joe

I understand what your saying but the ford guys seem to have success with single HW5200's on the 200-250ci Ford motors. The way I see it is if the monojet flows 240cfm, then if your curising at part throttle your not flowing 240cfm cause your not WOT. Just like a 4bbl at half throttle you would be flowing 120cfm correct?

A lot of the Jeep guys use the HW5200 on their
258 engines. They claim better throttle response,
better mileage and easier starting than what they had with the BBD's.
WWW.fordsix.com has some recommendations for re-jetting the HW5200 for use on the 200-250 Ford
engines.Should work on a 250 Chevy.

Gordy

You are probably right, I wasn't thinking straight or it was late in the night. Anything should be better then the Mono-jet! Joe

Well regardless I ended up with a 500cfm Holley 2bbl. Mainly for ease of possibly adding boost or nitrous. I have a Adjuta-a-jet from my 750dp that will work on the Holley 2300.