Harmonic Balancer

[NiceFishEh]

Just when I thought I had uncovered EVERY gremlin on this car in the last 5 years....

I was fooling around with the front sway bar when I looked up at the balancer, and on it it said...use with 340 cast crank only!

My 340 is definitely a '70 engine which is supposed to have a steel crank, which is also internally balanced.

I'm thinking obviously that this balancer should be on a cast crank.

I can't verify is someone has swap out the steel crank for a cast one without pulling the engine. I'm the 5th owner.

It idles pretty good right now. I don't race the car and seldom take it over 3K.

The engine does have a bit of a hum, not a vibration, at around 3K. Sounds a lot like a clutch fan sound.

I was told by the experts a few years ago that it's normal for 340's?????

Any harm in running this balancer or should I swap it out.

Thanks

Jim

 

[pastortom1]

I had a similar problem with a 70 340..........It had a harmonic hum, but at varying cysles per/second according to the rpm's........

It was annoying, and would rattle anything in the car that was loose.......

We closely inspected the balancer and found it has a counterweight bolted into the back side..........we removed the counterweight, and the problem was solved.

I would at LEAST inspect the back and see if there may be a weight back there........BUT, remember the rule of thumb that goes "If it ain't broke, don't fix it"...........If your car is not actually vibrating from a balance problem, you might want to leave it alone..........Without hearing it myself, it's impossible to say what I'd do in the situation, except to check that balancer carefully.

 

[moper]

If the car revs in neutral without shaking your fillings out at 3000 rpm, it was probably balanced with that balancer in place. No big deal unless it shakes like mad.

 

[NiceFishEh]

Thanks guys