I have this 84 trans am, My dad and I did a 350 swap in it cause the 305 was ****. I bought the block of a friend, and had it dipped and clean. Then we rebuilt the engine from the ground up. Its bored .40 over, over sized cam, 2.02 lifters, roller rockers, 750 holley, and the timing is set at 32 degrees I believe. Now the problem is when the alternator belt is on the engine runs like complete ****, and bogs when you give it gas. But when the belt is off the engine sounds beautiful, like its ready to race. We believe it could be a ignition problem but were not sure.. What do you guys think? This project is taking loner than expected.

The belt would not really cause an ignition prob to show up. It installing the belt drags the engine down that much, look at seized up parts that are turned with that belt.

Alt.. With belt off, spin the pulley.. Does it turn easy?
Water pump... Same thing

Are you using a mech/clutch fan bolted to front of water pump? If so make sure it can turn freely and not bind or hit anything.

All the pulleys seem fine, We do need to line them up better but, we believe the problems lie with the voltage. with the alternator connected there's roughly 15 volts on the system, without it there's a little less than 12.

Still will not be the prob. Normal alt. output is min of 13.2 volts to max of 14.5 volts... So "roughly 15 volts" sounds like it could be 14.5 and thats fine.

I did not mean to check if pulleys are good.. What I was saying is see how free the alt, water pump and fan turns w/o the belt hooked up.

Should be able to spin those items with no force/pressure using only 1 finger.

If it takes any force to turn the water pump, alt. or fan then that item is trying to lock up and that's the drag on the engine.

If it was a voltage prob it would only cause that kinda prob if voltage was too low (not too high) and not giving enough volts/amps to ignition system to fire the spark plugs

Is that 32 degrees of timing at idle?
Check the voltage at the big red/pink wire on the HEI, should be around 13.5 while running.