Do I go as big on main jets if.....

I have carbs with an accelerator pump? Using some rules of jetting with pods and four into one I should go up one pilot size and three in the main. But do I have go as high with the mains because of he pump? I know the pump does not help at wot but I was thinking that the main being bigger might b richer to help with acceleration.. What y'all think?


Knight Rider out!

What does your engine tell you.
My '79 ST,1105,.395,stock pumpers and exhaust.
17.5,,raised 1 and stock 110 mains
With an exhaust analizer idle was fine,mid range is rich,but top end went way lean.
I thought it was the 28s being to small for an 1105.
I'll try 115s and drop the needles 2 from what they are now.

Accel pump and main jet size would be unrelated. Pump will bottom its diaphragm around 1/2 throttle or less, stopping nozzle delivery. It is only a shot of fuel for acceleration, in the first 1/2 throttle or so depending on adjustment.

I agree the fact you have an accel pump should not play a part in the main jet size. Keep in mind the "rules" you mention regarding jetting for mods are just a general starting point and not what your machine may need in your location. You will have to test, plug chop, roll on, roll off etc or use an exhaust gas analyzer to find the proper jetting and tuning.

Thanks guys. Makes sense.

Knight Rider out.