Be careful here. The 1971 383 non HP engines had a cast crankshaft that will be externally balanced and require a balancer to match.
I agree, they are remarkably different. But the OP says he has a bad vibration. I don't believe the small amount of metal removed from that neutral balancer is enough to cause a bad vibration. I could be wrong. It's happened a lot. lolThey are easy to identify = there is a huge amount of Side weight present on the Balancer.
Out of the Millions ( I think 8,000,000 of 383 ) I believe that well less than one in a hundred
had the cast crank so the are not real common. I am not sure they had the same Design and
Diameter on the snout. I have not seen one for 40 years.
Man, you lucky * junkyard" dog! How cool is that! Musta been AWESOME!!!!!!!Another serious issue with a 50 year old balancer is that the rubber deteriorates
badly without being obvious from the outside. This causes the top to slip in relationship to the bottom ring. This causes a vibration as well AND as it slip makes the timing wildly inaccurate as the top moves in relation to the crank. I scribed line in the old days so I could see the top move. I had one actually explode on my Max wedge Car in the 60's and it made a heck of a mess and looked like a Grenade had gone off. It did it through the lights and left a crater that looked like a Land Mine went off!
If you car is fairly fast =
NHRA will NOT let you near the Track with the old stock one on your engine.
Also the Cast Cranks had a pretty large slab of a balance weight between two
of the Converter bolts near the outside of converter. Thru the 60s and 70s my Mom ran a large Wrecking yard in So Cal. I saw an awful lot of odd stuff and that
is from where most of my stock parts came from that I still have in the shop today!
How do I tell if the crank is original?Might want to check your crank to see if it is stock. Someone may have put new pistons in of different that stock weight, so they rebalanced the rotating assembly and drilling the balancer to make up the weight differences needed.
Check your flywheel too for extra holes other than stock. Or an odd shaped flex plate. 383 should be neutral balance engine.
Correct, typically the inertia ring is drilled to balance the damper assembly in production. Drilling the balance holes at a larger radius gives you more balance correction. As GTX John stated, those balance holes may have been drilled in the damper hub to balance the rotating assembly, has merit here. 65'It may just be an optical illusion, but the ring on the bal hub looks thicker towards the bottom......which would require those holes to try & balance it. Usually the ring gets drilled to balance the unit, not the hub.
Correct, typically the inertia ring is drilled to balance the damper assembly in production. Drilling the balance holes at a larger radius gives you more balance correction. As GTX John stated, those balance holes may have been drilled in the damper hub to balance the rotating assembly, has merit here. 65'
I tend to agree. This thing rattles my fillings out. I’m just not sure what else it could be.I agree, they are remarkably different. But the OP says he has a bad vibration. I don't believe the small amount of metal removed from that neutral balancer is enough to cause a bad vibration. I could be wrong. It's happened a lot. lol
It’s a auto. No weights on the converter.Automatic or 4 spd ??
Cut your oil filter open, poke a hole in it with a scratch awl and open that hole up to 1/2" with a punch, then zip around the can with an aviation snips. 1" down from the gasket seal end on the filter. See what's in there. If clean go on to looking at the torque converter.
Something that is shaking that bad has got to be a miss matched external balanced torque converter to an internal balanced enging. You have extra weights slinging around there that should not be there.
Also you may have an External balanced 360 Flywheel bolted on your internal balanced 383, they will bolt to the cranks, 318, 360, 383, flywheels all bolt up to the same crankshafts.
Is this a new engine swap into an old drive line of a different car that just came up on this build. Or is it an existing drive line where the vibration just started out of nowhere ???
360 external balance flywheel:
View attachment 1715810378
360 External Balance Flex Plate:
View attachment 1715810379
View attachment 1715810380
Take the weights off for internal balanced engines:
View attachment 1715810381
For external balanced engines going to internal balance flywheels:
View attachment 1715810382
Lots of combinations to get it wrong, need to make sure you have the right combination to get it right.