I have just purchased a 1971 240z with an l28 engine I found a vacume leak at the base gasket of my front su

now i have fixed it my z wont run right it is like it is running on 5 cylinders

but no mater what lead you pull of it makes no diference and it is blowing lots of black smoke i am guesing it is runing rich but i dont know how to lean it out? I know stuff all about su carbs (round tops)

if you could think of any other thing it could be please help?

i got it back from the mechanic today

he droped the needles a bit so it would not run so rich at idle

but it now runs lean at higher revs.

I was wondering if the 240z su' are to small for the l28 motor?

if so would a neadle change fix that?

Zs that currently hold hillclimb records here locally running ZTherapy standard production carbs..... Nothing oversize about them.