...and that's what she said too????
What weight harmonic balancer is right?
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
What weight harmonic balancer is right?
I posted an earlier thread re: vibration as revs build. I've asked a bunch of mechanics and they felt the harmonic balancer is bad and this seems to be the most likely problem, but to also check flywheel pully, motor mounts, trans mounts, u-jouins (though no vibration when disengaging clutch at speed).
I just checked auto zone and there's a lot of different weights.
10.55 lbs @ 138.99 heavy duty
8.16 lbs @ 61.99
10.55 lbs @ 58.99
What do you guys think?
Thanks, Glenn
I just checked auto zone and there's a lot of different weights.
10.55 lbs @ 138.99 heavy duty
8.16 lbs @ 61.99
10.55 lbs @ 58.99
What do you guys think?
Thanks, Glenn
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I've seen questions like this one before. And there are lots of answers. The thing is most of them are right in one way or another.
As far as weight goes, it's all part of the inertia equation, More mass will help launch the car. Also will help prevent the twisting motion of the crank when cylinders fire. But if that's the case, why (and how) do some class racers get away running nothing but a hub?
And diameter? Well take a 1oz fishing sinker, tie a string on it that's 6" long. Swing it and feel how much pull it has. Now make the string 8" and do it again. That 1oz sinker feels heavier. Same with an 8" balancer, even though it weighs the same as a 6".
Go figure.
BTW- I run 8" balancers on SB's and an aftermarket tab, or a cover that has the 8" tab built in.
As far as weight goes, it's all part of the inertia equation, More mass will help launch the car. Also will help prevent the twisting motion of the crank when cylinders fire. But if that's the case, why (and how) do some class racers get away running nothing but a hub?
And diameter? Well take a 1oz fishing sinker, tie a string on it that's 6" long. Swing it and feel how much pull it has. Now make the string 8" and do it again. That 1oz sinker feels heavier. Same with an 8" balancer, even though it weighs the same as a 6".
Go figure.
BTW- I run 8" balancers on SB's and an aftermarket tab, or a cover that has the 8" tab built in.
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
So...matching what's on the engine now isn't that critical? By your description heavier would be better for launch, but won't it take the engine longer to build rpm's?
Thanks, Glenn
Thanks, Glenn
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Chevy ran an 8" heavier damper on the High performance engines. It dampens harmonics better in a high performance application. Higher compression, higher rpm and more cam duaration and overlap contribute to more harmonic vibration. The 2 lb weight difference at the damper doesn't matter much on how fast it revs. It is rotating weight Vs reciprocating weight. The rotating weight at the flywheel will make a noticable difference going from a 30 + lb stock flywheel to a 15 lb. aluminum. The reciprocating weight of the crank rods and pistons make a noticable difference in how fast it revs if you reduce weight there but it is hard and expensive to reduce weight and still maintain strength.
Last edited by 63mako; Apr 24, 2007 at 11:44 PM.
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
Thanks for the input guys!
How would a harmonic balancer go "bad" so to speak? It's solid metal, correct? I did a visual check this AM and everything looked ok. I haven't noticed any wobble or alignment issues when running at idle. One mechanic mentioned there's a piece of rubber on it that may have worn out. WHat rubber? Is there something else that causes this kind of vibration I haven't mentioned or should check for?
Glenn
How would a harmonic balancer go "bad" so to speak? It's solid metal, correct? I did a visual check this AM and everything looked ok. I haven't noticed any wobble or alignment issues when running at idle. One mechanic mentioned there's a piece of rubber on it that may have worn out. WHat rubber? Is there something else that causes this kind of vibration I haven't mentioned or should check for?
Glenn
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Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Thanks for the input guys!
How would a harmonic balancer go "bad" so to speak? It's solid metal, correct? I did a visual check this AM and everything looked ok. I haven't noticed any wobble or alignment issues when running at idle. One mechanic mentioned there's a piece of rubber on it that may have worn out. WHat rubber? Is there something else that causes this kind of vibration I haven't mentioned or should check for?
Glenn
How would a harmonic balancer go "bad" so to speak? It's solid metal, correct? I did a visual check this AM and everything looked ok. I haven't noticed any wobble or alignment issues when running at idle. One mechanic mentioned there's a piece of rubber on it that may have worn out. WHat rubber? Is there something else that causes this kind of vibration I haven't mentioned or should check for?
Glenn
"Fluid" dampers are hollow metal with a thick silicone fluid inside.
Thread Starter
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
It is not solid metal. It is a metal "ring", bonded to a metal "hub", with elastomeric rubber. When the rubber gets old, brittle, they can slip. When they do, they get off center and "wobble", causing severe vibration.
"Fluid" dampers are hollow metal with a thick silicone fluid inside.
"Fluid" dampers are hollow metal with a thick silicone fluid inside.
Glenn
Burning Brakes
Joined: Feb 2006
Posts: 1,024
Likes: 1
From: AL
there will be only a best compromise for the “size” of a harmonic dampener. “size” means mass, spring rate, and/or viscous damping, and this will all boil down to an isolation efficiency. that is, you may have a good dampener with a poor efficiency for your engine combination. i’ve never seen any of these values published, maybe someone here will know. the best way to get a balancer that works best may be to use the experience of a qualified engine builder, or aftermarket dampener mfg's should know what to recommend.
if you have a bone stock, or just warmed up engine, the factory dampener should be fine. just check the elastomer for integrity as mentioned above.
if you have a bone stock, or just warmed up engine, the factory dampener should be fine. just check the elastomer for integrity as mentioned above.
