1999 Firebird 3.8 V6. If I spun a bearing, should I have the heads checked?? I bought a rebuild kit and crankshaft. Replaced everything except heads. It starts up but has a rattle when I take off.
Any ideas. Haven't even broke in motor.

You didn't have the heads worked? Why?

I believe he said the heads were fine. This is all new to me. Will a spun bearing damage the heads?

Who is he?
Only if it allows the piston to hit. Not likely unless she let go and you would know it.
I assume this is an auto trans. Did the blots for the torque converter get torqued down good?

Yes. It is an auto trans. Yes the converter was torqued to specs. Is it normal for it not to be as quiet as it use to be? Maybe its just me, but it sounds alittle rough. Someone said it could be a dead cylinder but my coils are new, plugs and wires are new, sensors are new and connections are good.

I'm sorry, when I say "he", I am referring to my son. He graduated UTI and he is the one that rebuilt my motor.

So the engine currently has a spun bearing? . . . or it has already been repaired after having a spun bearing in the past?

What was done to repair the engine? . . . primarily: what was done to repair everything related to the spun bearing?

The spun bearing is the reason we rebuilt the motor. Bought the master rebuild kit plus new connecting rods, timing chain, gears, oil pump,
crankshaft. Soaked new lifters. Torqued everything to specs.

What is the clearance on the rod and main bearings?

Could you explain a little more about where the "little rattle" is coming from? Is it the front of the engine, back side, or upper part? It'* hard to diagnose here, without even knowing where the rattle is coming from. All anyone can do is speculate!