ok, so im not sure if this is what caused it, but today i tried to.."tune my carbs," meaning that i tried to make the mixture right. i twisted it all the way counter clockwise (which i think/hope is lean) and then i turned it two and a half times clockwise (they're stock SU's on my '72 240Z). there is now a bunch of smoke coming out of the exhaust, and when i was driving it i would step on the pedal and it would almost feel like i was engine braking, my car would actually SLOW DOWN when i stepped on the gas..

did i do something wrong?

what might have caused my car to do that?

Did you balance the carbs air flow? If the balance is off the carbs cant otherwise be set. Backing out the nozzle 2 1/2 turns is only a starting place to get the engine to run , so you can warm it up then adjust the mixtures . Use the search feature, there is all the information you need there and more on this issue. I am vary willing to help. If you cannot find what you need there send me a PM. Gary

Gary is on the right track. Do you have a unisync tool?

If you search the SU questions forum, you will find your answers. Paul at Z Therapy is an excellent source of SU wisdom.

Gary is on the right track. Do you have a unisync tool?

If you search the SU questions forum, you will find your answers. Paul at Z Therapy is an excellent source of SU wisdom.

ditto on that.. i bought one of his tuning videos awhile back.. helped a great deal.

is the timing correct? valves adjusted? Getting good spark from the coil? (that gremlin cause me a track day once)

Gary is on the right track. Do you have a unisync tool?

no, i don't..