Balance Problems...Vibration......

moper said
If it's a '70, it should have a forged crank. If they used an aftermarket piston andd did not re-balance, it will vibrate just like you say. If it's a cast crank, without the right matching dampner and convertor, it will vibrate like you say. A cylinder misfire will not get better or worse...just speed up with rpm. In any case. Do Not run the engine any more. If you feel it, guess what it's doing to the engine's internals and block. I would start with pulling the oil pan and taking a good look-see at what you really have. Also, the balancers BJR speaks of are what I use too...And I just got one for an LA engine shipped from CA to CT for $70 new in the box.

just because the block is a '70 block doesn't mean a thing i've been to machine shops and professional motor building shops where they have racks of cranks. they buy cores, split them up and part them out. they could have got in the motor and swapped the crank with another instead of messing with the original to be turned and stored at a later date. a crank is a crank? right? just kidding! there is also a difference in 318 to 340 forged cranks, the 318 won't balance out to a 340 because two of the rod throws on a 340 are drilled to lighten the crank rotating mass weight to offset the heavier rod piston combo.just a bit of info i found out the hard way. hope you figure it out so you can enjoy your sweet ride!