I recently bought a '71 Dart, 318/904. It has a vibration. The balancer appears OK so I checked the flexplate and converter. No cracks in the flexplate, no missing bolts.

I looked for 360 weights on the converter and found nothing on the flexplate side of it, but on the side toward the transmission; welded to the outside of the converter body; I can feel a weight about 3 inches long and less than 1/8" thick. The converter looks like it might be a replacement, shiny black paint on it.

I'm pretty sure the converter is causing the vibration, but I've never seen weights in that location.

Oh, yeah... and it looks like the vibration has taken it's toll on the starter ring. Not a great pic with the phone in one hand and small light in the other, but it is cracked.

On a good note, I might have figured out the vibration that has kept the previous two owners from driving the car very often.

thin plates on the curved part of the TC are to bring the hunk of metal to neutral balance during manufactureing then large weight or weights are added on the front flat face if it is externally balanced. If that's the case here it's neutral. I'm assuming it vibrates in park also. Might be an internal (bobweight) balance problem but that's worse case scenario. I'd wanna get ahold of the person that built it for some direct info

Great opportunity to add a properly balanced higher stall convertor...

BTW a 318 is neutral balanced...

Are you sure the engine is still a 318? Any chance someone swapped a 360? & didn't use the 360 balancer/convertor.. Look at the cast in number on the drivers side of the block above the starter..

RT said 318's are neutral so if the damper is correct then sounds like the TC needs to come out & hopefully that's it EDIT that'd sure explain alot if it is a 360 cause the TC from your descrip is neutral and it'd be pretty hard to mistake an externally balanced damper for the correct neutral 318 one so I knew we were missing something easy just couldn't see it assuming the bobweight #'s are good inside

bring the piston to top dead center and check the timeing mark on the damper to see if it has sliped any. just cause a 30-40 yr old damper "looks" good does not mean it has not sliped.

I would think a N balance TC would not go out of balance unless it lost a weight off the side of it.

has the engine been rebuilt sometime in its life since 71? could be off balance with replacement pistons/rods ect..