teapot3208

What is the difference besides size and how close the timing tab is to it? I have an 8" one on my car now, but there is a 6 3/4"? one laying in my garage. If I put it on, will there be any difference in my performance? I was thinking like an aluminum driveshaft, lighter and less rotating mass. Or am I just having a brain fart?

Stekman

Bigger "absorbs" more vibrations, smaller makes for less rotating mass. Minus the timing tab/etch mark location, sizes can be swapped, assuming it's internally balanced.

rx7speed

also would think size would make a difference as far as what vibrations are effectivly damped. larger one should work better for lower pitched vibrations as a smaller one should work for higher frequency I wuld assume.

dont know though for sure. only owned one car that I know of that had a damper unless my 74 maverick I6 had one. but the other cars piston/rotary haven't had one


EDIT: now that I mention that why wouldn't my other cars have a damper on them? my rx7 I can kinda understand in a way but my honda, and celica didn't have as far as I know. the honda for sure doesn't have one just a flywheel and a normal pully that's it. but they are I4's also. do the V6 cars have one? and whats with some cars with a counter rotating shaft or something like that?

Stekman

Your app's might internal balance shafts? The v6's in the thirdgen's I think run the external damper setup.

rx7speed

the honda just has a crank and cam as far as I can tell from the outside. the mazda closest thing is has to a balancer is on each end of the crank is has a big hunk of metal kinda like a crank weight.

Vader

The term "balancer" is a bit misleading for most engines. It is actually a torsional damper, intended to absorb potentially harmful crankshaft harmonic waves which could otherwise contribute to crankshaft stress and failure. Except for a few engines, the torsional damper does nothing to truly balance the rotating assembly.

Several engines use balance shafts to help counteract power pulsations in the engine and contribute to a smoother running assembly. They do so via a shaft or shafts with eccentric weights (much like a camshaft) that rotate in time with the crank to counteract the overall engine vibrations caused by cylinder firing/power pulses. They also add rotating mass.

I can understand why a truly inherently balanced engine might get away without a torsional damper (like a horizontally opposed arrangement or full radial) but a V-engine probably should have something to dampen crankshaft harmonics. The same could be done at either end of the crank, such as with a flywheel with some higher frequency energy absorbing capability.

IHI

iTrader: (1)

You'll "see" no difference at all using a smaller 6 3/4" damper as opposed to an 8" damper, but the 8" will promote longer engine life due to absorbing the vibrations that will literally shake the thing apart and wear parts quicker if using a small damper.

Fast355

iTrader: (2)

IMO, GM put the 8" balancer on a forged crank in their HD 305/350 trucks for a reason. HD use puts stress on the crank.

rx7speed

how are these balance shafts spun?
is there a way to find out if you have one from the outside?


the counterweights are what runs on my rx7. not a damper so your right there vader and they are attached to the crank though not a seperate ashaft