Horder wrote: ↑Mon Dec 26, 2022 7:44 pm
We have a highly respected carb guy in our city. He always told me a 750 was the answer.
Maybe you could work something out with him to loan a 750 to see how you like it? In his interest if you are to be a potential customer.
I agree with Colaradoracer’s first post that a lot has changed over the years that can allow carb size beyond the old formulas to work effectively. It has to be remembered that carburetors are not cfm devices but air/fuel density regulators. If a larger size can supply a higher air/fuel density at any given rpm
while still providing a satisfactory homogeneous mix with minimal delay in response to throttle angle change (does not need excessive acceleration enrichment) then it will always do better
performance wise than a carb with a smaller cfm rating. There are going to be upper limits where that becomes difficult to accomplish with diminishing returns, eg the old 850cfm dimensions of 1.56” venturi X 1.75” throttle bore would be finicky to tune on your engine to out do a 750 on the street.
Different carb dimensions bring on the change of air/fuel density at different rates, especially with throttle bore sizes. In this respect on the street when the throttle is modulated a lot, pinpointing a size through theoretical methods should take a backseat to driver preference.
So see if you can borrow various sizes to feel the difference (yes, I know they won’t be dialed in exactly to your engine) and when settled on get yourself something in the preferred size and fine tune. In the meantime Toms suggestion of trialing 1:1 linkage of your current carb should give you informative feedback.
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.