Flywheel or harmonic balancer

[soxx35]

hi I have a vibration in my 79 l82 4 speed. i got it down to either the flywheel or harmonic balancer. because it vibrates even if im idleing in neurtral. how can i check which one it is
thanks rj

 

[Ala75Vette]

well, I'm far from being an engine expert, but I do know it's a lot cheaper & easier to replace the harmonic balancer than to pull the tranny off and service (machine) the flywheel (and replace the clutch...). Personally, I would suspect the harmonic balancer, but hopefully other more experienced mechanic-types will offer their advice, too.....

 

[cruzer99]

I agreew with 75VETTE, do the cheap fix first. Odds are that it is the HB, they are nortorius on higher milage motors.

 

[AKRAY4PLAY]

i may be wrong, but the harmonic balancers on 350's are neutral balanced. so if the balancer slipped, it should still be in balance just timing marks would not line up. if you have a 383 or 400, then you would possibly need a counterweighted balancer and flywheel depending on the crank being internal or external balanced. have you looked at the tuning conditions of the motor?? a couple of fouled plugs/misfiring cylinders would give quite a vibration. you could do a simple inspection to see if the crank is bent. pull the spark plugs and have someone crank the motor. look at the harmonic balancer and flywheel (through in spection plate) and see if they wobble when turning. my father's boat motor bent a crank for no apparent reason. Brian

 

[JohnZ]

Brian's got it - neither the balancer nor the flexplate has anything to do with engine balance (except on 383's, 400's, 454's, and post-'85 350's); I'd suspect a basic tune-up-related problem or a driven accessory issue. Pop the belts off and see if the idle vibration goes away - if so, it's caused by one of the driven accessories. If it's still there, go after an ignition-related miss.

 

[Scooter76]

True, the balancers & flexplates/flywheels are netural balanced on 350's. But the balancers are two seperate peices,bonded together by rubber. They are balanced as a unit. If you look at a ballancer on the front there will usually be a series of shallow holes drilled, this is where weight was removed from the "heavy side" of the balancer. If anything was to shift (outer ring moving to a diffrent position on the inner ring) then the neutral balance can be lost. It would probobly have to move quite a but to really disturb the balance enough to cause problems though. So it is probobly not the problem here.
Not trying to be disagreable with anyone here, just trying to give some info on balancing. I work on electric motors for a living & part of my job is balancing various components. We use a machine that is very simmular to the ones used to balance crankshafts.
Have a good one!