1986 Harmonic balancer?

[Patio]

Anyone know what a "harmonic balancer" is and what it does, how much should it cost, and whats the symptoms of one that supposedly
broken in half?

 

[JonM]

Its purpose is to cancel out "torsional" vibrations created in the crankshaft by the engines power pulses. Crankshafts actually twist a small amount every time a cylinder has a power stroke. A stock HB should cost around 70-80 dollars at your local parts store.

 

[vigman]

There are different sizes & types

All 327 & 350's are INTERNALLY BALANCED
( meaning crank/rods & pistons are the same weight/balance) So the harmonic & flywheel are balanced unto themselves.

400's are not ( not sure about big blocks)
You need an OUTA BALANCE Balancer to counteract ( neutralize/offset ) the mass flying around.

So the SMALL harmonic balancer is 6 inches the BIG one is 8.... the object of the game is sort of like a gyro... as the harmonic spins up the harder it is to move off center.. the more mass.. the truer it will run ( assuming the crank and all are running true as well ).

The heavier the flywheel & harmonic combo
the more HP you need to turn it.

MOST after market balancers are balanced "better" then the stock ones.

But it's no miracle cure and you will not get extra hp...
Your buying a better paperweight
That you know
a) The timing marks are correct
b) Will be better balanced then the stock GM ones... but your past the point of diminshing returns.
c) Sure is pretty! It must go faster.


Now the stock ones typically seperate between the rubber & the outside weight that has the timing marks... If it slips.. you cannot time your engine.. if it slips to far it will make a mess outa things under the hood.

Vig

 

[Eagle85C4]

I replaced mine for 32.00....I got it at Murrey's auto parts....

 

[Grzldvt]

These balancers have a tendency to separate. It is a two piece balancer. If you look at the picture JonM supplied there is rubber/nylon between the 2 pieces. When they get old it gives out the the pieces separate. The outer portion on mine slid back and was rubbing agianst the timing cover. It is a small pain to get out, because the steering rack portion of the frame is almost in the way. You will see a notch in the PS lines, where you can get an extension through them to pull the center bolt and the crank on the puller.

 

[Jack]

If a balancer/damper separates or breaks in half ... the motor will vibrate heavily and things will begin to crack/break. There's a lotta opinions whether one should use the stock elastomer-type damper/balancer or a big-$ fluid-filled type. GM uses 8" elastomer balancers on even their hot crate motors. A leading manufacturer of hi-po stroker crankshafts (SCAT) also recommends an elastomer balancer. Sure the rubber can fail and the outer ring can slip ... but usually only after many years of attack by heat & oils ... & trying to remove one by prying on the outer ring will accelerate the process. Many vette sbc came with the 8" elastomer damper. Far as I know, sbc 400 came with 8" external-balance damper. IMHO, if an 8" balancer will fit, most street sbc's will do fine with an 8" elastomer (aka rubber) balancer.
JACK:gap