Goldrocket

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.

gerald m

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 .

Goldrocket

Thanks for the input!