[mrmustang]

Jake,

You take the engine cubic inch and multiply by the maximum RPM and divide by 3456. If you have an automatic transmission you will need a vacuum sec. carb, a standard transmission can use a Double Pumper carb. For this to work, you need to get yourself up on a chassis dyno. Sure you can make a larger carb work for maximum full throttle performance, but if you want a carb that is going to handle every day driving, along with your performance needs, then your going to need to drop down in size. Again, get yourself up on a chassis dyno that offers at least HP, torque, and air/fuel ratio and you'll then see what I mean.

Now, with that said, in my case I have a 427 side oiler, solid lifters, 9:7:1 compression, and a Lunati cam, single low riser intake and originally a 780cfm Holley DB (438hp, 468ft/lbs of torque at the rear wheels). After two hours fiddling around with this car on the chassis dyno I took the advice of the owner and used the formula above, dropped down to a 600CFM Holley 04776C DP (some people called me crazy telling me I needed at least a 750DP but the vormular above does not lie) and stepped up with a larger PV and some jetting of the carb. While I lost 3hp and 7ft/lbs of torque at the rear wheels, I gained more performance out of the carb, sharper throttle response, smoother air/fuel ratio across the power band, and a driveability that I had not had before. While the numbers went slightly down in my case, I'll bet performance wise I'll actually be a few seconds faster in the 1/4 mile next time I'm at the strip. So again, when I stated above that bigger is not always better when it comes to the carb you select for your engine.

Hope you find this helpful.

Sincerely,

Bill S.