Maybe he will get some answers over the weekend, I really don’t think changing or trying to tune the rate of the accelerator pumps is going to help matters any. I think the carb is just too big. It’s about 100 CFM too much for that engine. That 496 even at 6,000 RPM and at 100% volumetric efficiency would only require 861 CFM. He says it runs good mid range to top end okay, that’s because there is enough piston speed to create enough velocity at the booster venturi’s to pull fuel through them. Also lowering the power valve opening rate can cause a rich stumble because again velocity isn’t high enough to handle the additional fuel along with poor atomization. Maybe in time one can tune around this problem to mask it, but it’s still not going to be right. Old school hot rodders rule of thumb to follow with carburetion is…run as little carburetion that you can, without sacrificing performance. In other words, run an engine with a CFM size that may be a tad on the smaller side because the signal at the boosters will be very high to pull fuel, the response will be much better and you will have better atomization due to higher velocities and turbulence and that alone will make more power because you are handling and managing the fuel better. On the other hand much too small of a CFM rating will just choke the engine down at mid range and top end, drastically affecting HP potential. The better the atomization, the more you will burn during the combustion process, remember any fuel not burnt is wasted potential energy, and raw fuel doesn’t burn.
