Winfield SRBB CFM

[Pat_n_Pat]

Does anyone know the CFM for a Winfield SRBB? We need to compare our Winfields with other carbs for replacement. We have oodles of documentation, but no flow rates.

Thanks, Pat

[NTX5467]

CFM flow rates didn't become popular until the later 1960s, which probably greatly post-dates your carbs. Before that, in the later 1950 and earlier 1960s, it was "venturi area" which was a comparison factor. Throttle bore diameter seemed to be secondary, although probably directly related to the diameter of the carb's venturis in some manner.

So, compare throttle bore diameters first, then the diameter of the venturis. If you want some comparisons . . . the Holley 2bbl 500cfm carb had 1.69" throttle bores, but a similar Rochester "big 2bbl" with 1.69" throttle was more like 450cfm. The Rochester "small 2bbl" with 1.44" throttle bores was probably closer to 300cfm. The multitude of 2bbls with 1.56" throttle bores were probably about 375-380cfm (my estimate).

The other thing abour carb flow rates is that, as I learned in a HP Books book on Holley carbs, 2bbls are rated at 3.0" Hg pressure drop and 4bbls are rated at 1.5" Hg pressure drop. Not quite equivalent between 2bbls and 4bbls, but as long as the comparison index is the same for either type, then cfm figures can be used for comparison. I guess the rationale is that on a 2bbl motor at WOT, there'll be more vacuum than if there were 4 larger holes openned to the atmosphere?

Just some thoughts,

NTX5467

[Pat_n_Pat]

NTX5467:

Thanks for your thoughts.

I never remember using CFM comparisons back in the late 50's and 60's. I was just hoping someone had put a Winfield on a bench. Of course, Strmberg 97 and 48's were carbs of the same era.

The throttle bore for the Winfield is 1.48 c.i. and 2.22 c.i. for the Stromberg 97 (2x1.11 c.i.).

The Stromberg 97 specs flow 162 cfm, calculated like a 4 BBL at 1.5" Hg (I see a lot of people now going to the 1.5" Hg number for comparison purposes).

As to venturi area, we can get the info on the Stromberg, but the Winfield works more like a variable venturi carb. The Winfield has a straight bore, so you could say the Winfield has a 1.48 c.i. venturi, and 1.47 c.i. for the Stromberg.

Since we ran very well in the 2011 Great Race with one Winfield (except when we tried to stop fast), I am assuming that we will probably run well with one Stromberg 97.

Any thoughts?

Pat