need Main Jet jetting advice

[marddy]

Hi,

I would like to continue using my 250's Carbs on my converted 350 YPVS with 31K Cylinders. These Carbs has Power Jet - LHS Carb is having 40 and RHS is 50.

Kindly advice what should be the Main Jet size. I am currently using 180 and she is fine.

[bryan]

You can Stick head race ball bearings in the pipes and jet as 31K at 140 mains if you want to get control of the overly rich standard jetting, F2 power jets have 185 but 60/65 power jet I think. You would be wanting to get it to 240 combination on both and do plug chops to see what colour you have. Power Jets were used to make the very top end overly rich so its not the best for performance as you can't swap the jets.
You should also look at swapping the needles and pilot jets to the 350 ones too!