swapped to a 350 in my 82 TA, I get a pulsing vibration when driving, so I check it in park and I get it as well (although not as strong). I can't figure out what it could be, to me it seems like the engine. I got it from PHX musclecar in PHX, they told me it was balanced before it left the shop. the only thing I can possibly see as a problem is it has a weigh on the flexplate. is this common? this would lead me to feel a pulsing feeling. especially when bolted to the coverter then the coverter, wouldnt' the coverter have to be counter balanced? any ideas? (everything is new too,balancer, flexplate,motor mounts ect)

 

The presence or absence of a weight on a flywheel doesn't imply that it's balanced or unbalanced.

 

so does that mean I should focus elsewhere? driveshaft is new (double check balance yesterday, as well as rear tires) rearend is new, tranny is new engine is new. all mounts are new. i'm at a loss, i've tried to isolate it but it's really hard to figure out when going down the road. all I do know it that it's rpm sensitive, not speed, the pulse gets more intense the more rpm/speed, so in otherwords it's always there. any suggestions?

 

I'd be talking to the people who built your engine.

 

take a close look at the crank pulley and see if you notice any movement out of the ordinary. I've ordered engines and had the harmonic balancer bent out of whack from shipment.

 

I did check the crank pulley and it is smooth, (i even replace the crank pulley to rule out that). should I try and replace the balancer, is that a possibility? If I do call the engine builder my problem is how to I absolutly veryify it's the engine, the engine builder will tell me it is another component? any advice?

 

it just donned on me that you mentioned that you have a weighted flexplate on a 350. that engine should be internally ballanced, call your engine builder and find out why he has installed this flexplate. you just might have an imballance issue. the smallblock 400 was the only one to have external balancing.( except the 383 which uses the 400 crank, which is a custom build)

 

This is really a semantics issue. The one-piece rear main seal crankshafts required a weight on the flexplate. That is different than the externally-balanced 3.75" stroke 2-piece rear main seal cranks.

Before this discussion can proceed any farther, we need to know if this engine has a 1-piece or 2-piece rear main seal crank.

 

One piece main seal. I called my engine builder and they told me everything after 87 used the flexplate with the weight. or at least 87-95. why does a 2 piece main seal not need a weight or why does the one piece seal?

 

In order to accomodate the round 1 piece RMS, the mass of the irregular-shaped 2 piece RMS crank flange was moved to the flywheel.