Ok, I joined here a long time ago, but I've not been on these forums much. So I can't post in the regular sections. Here goes, I have a 13B street port that is about to get a Proform 650 double pumper. Before we go down the "wrong carburetor road", please bear with me. I had the dual Weber DCD set up on the car, ran decent, but power dropped off hard at 8200 RPM. They had no bottom end and after more research I found that they only flow 230 CFM each. The car was tuned on a chassis dyno and the AF ratio stayed between 13.5 and 12.9 through the entire RPM range. The carbs were great, but would work better on a stock port motor. I spent an entire day on the dyno, they were as good as they were going to get. Anyway, I have the Profom 650 (Holley with billet throttle body, metering blocks and bottom plate) on the way. I can get it tuned, I have an AF gauge in the car. My question is, does anyone have a starting point for jet size with his 650 Holley, 13B street port combo? I live in Colorado Springs, so 6700ft. Any starting point is fine, I can make adjustment quickly, just not sure where to start. And any recommendations for accelerator pump sizes as well. I know I'm going to spend more time getting the air bleeds right, but this carb has them right on top.

 

Just start with what ever it comes with and be prepared to go up as much as 5 to 6 sizes as far as the squirters you shouldn't need the big pump just make sure it is set up to give a good healthy squirt the same time as the plates start to move . If the throttle plates open before the squirters supply fuel it will more than likely have a bit of a lazy spot for a tiny bit . That will get you started but don't be surprised if you need to do some power valve work .

 

Thanks for the input!