I have a 400 small block that came with my car when I bought it.I need a flywheel and all that but was wondering if there is a way to tell if it's internally or externally balanced. I'm new to american cars so I'm learning. Thanks

from what I remember, all sbc 400's came externally ballanced, so unless someone built it for high HP and had it internally ballanced then it should be externally ballanced

Yes, all stock 400's were externally balanced. If it's an automatic, there is a strip of metal plate, about 1/2" wide by 4" long, welded to the engine side, right up at the bottom of the ring gear. If you take the inspection cover off and have someone rotate the engine, you'll find it.

If it's a stick, there will be a large "bump" in the concave engine side of the flywheel, again, out at the edge, by the gear.

Sounds like you don't have a flywheel/flexplate or balancer on the engine? In that case I would pull the pan and look to see if there is any heavy metal welded to the crank. If not you can be pretty sure it is still externally balanced. If it has stock rods and pistons you can be pretty sure it is externally balanced. With no flexplate/flywheel or balancer the only way to tell, is to pull the pan.

I think we all are missing something here..

Please post the letters at the end of the VIN on the motor pad above the pass. side water pump's upper bolt so we can decode just what you actually have..

pdq67

On the front I have c7u110341 (not positive of 3rd digit)and f0825tlu. Above the oil filter I have 330817 and h12-78.If theres more just let me know thanks

Aug 12 1978 casting date 400ci K30 & 3500.Big truck engine. Unless it has been rebalanced from the factory it was externally balanced.

Thanks, I hope this thing isn't a pig when I get it out on the road.

depends on what's on/in it. With some good heads and a lil cam upgrade, 400's go really really good.