i just put my new 401 in my wildcat and it was turning over and it fired once i turned it off and let it sit,when i tried to start again its like the starter doesnt have enough torque to turn the engine.i checked all obstructions and other thing but when i try to start it turns real slow and will jump occasionaly.starter is smoking from not being able to turn.i put in a another starter not a new one but one that worked.same thing.when i take out the spark plugs it turns fine.please help.

You say a new engine. I assume you mean a rebuild. I'm not sure I follow what it is you are tryimg to describe, but if I do understand then you may want to be sure the valve timing right.
Does it wind okay and want to fire then start poppin' and fartin' (backfiring) then fire again then backfiring, like in a cycle? I saw this happen once. I put a timing light on it and had it cranked over. I watched as the timing mark moved every revolution.....going complete 360's as it cranked. I discovered that the timing chain was skipping over a sprocket that was missing some cogs.
Don't know if this is relevant to your troubles or not....but for what it's worth....there you go.
Good luck. Keep us posted on your progress.