are syty's internally or externally balanced

T

the Sandman

Member
MOST SyTy engines are externally balanced

MOST SyTy engines are externally balanced

MOST SyTy engines are externally balanced - not all. The engine being built for my Syclone is being converted to internal balancing. It's not that big a deal, costs around $200 extra and involves drilling holes in the crank counterweights and pressing in some heavy metal - in this case Mallory Metal. The switch to internal balancing takes a significant amount of end flex out of the crank. This is one of the ways Dennis and my crank guy are protecting my stroked stock crank (damn that sounds funny).
 
M

Methuselah

New member
I learned something today.

Post 1986 4.3L v6s are externally balanced. I would have known this had I needed to buy a flywheel, as pre 85 flywheels are neutral balanced.

Are our engines externally balanced by just a counter-balanced flywheel?

I was confused, I think, by the fact that internal balancing happens with the crankshaft. The crankshaft counterweights are modified to balance the weight of the piston and rod assembly. Its easier and cheaper to remove weight from the crankshaft counterweights by drilling out material. In fact, someone had mentioned to me that his machinist prefered the TRWs because he simply had to remove weight from the crankshaft to balance it.

So the rotating assembly must be balanced with the flywheel on, right? Why have I not heard of SyTyers getting a neutral balanced, lightweight aluminum flywheel when rebuilding their engines?

Please clear up my misunderstanding, and I am very sorry for my misinformation.

Thanks,
Seth.
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T

the Sandman

Member
Are our engines externally balanced by just a counter-balanced flywheel?
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Yes.

So the rotating assembly must be balanced with the flywheel on, right? Why have I not heard of SyTyers getting a neutral balanced, lightweight aluminum flywheel when rebuilding their engines?
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Correct. A major drawback to this setup is that once the engine is balanced if one part needs to be changed such as the flexplate or dampener the engine will (probably) no longer be balanced.

If we ran manual transmissions with flywheels there might be some benefit to going with aluminum. But with the auto trans flexplate, which is already pretty light, there would not be much benefit.
 
M

Methuselah

New member
the Sandman said:
If we ran manual transmissions with flywheels there might be some benefit to going with aluminum. But with the auto trans flexplate, which is already pretty light, there would not be much benefit.
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Great, Ive got a handle on things now. Thanks for the answers, and Im glad I was given the slap down *before* I approached a machinist.

Seth.
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canadian

canadian

sy in progress
so what happens in the situation (where i'm at now), where i have to replace the balancer on the front of the crank? does everything need to be rebalanced or can i get away with putting another stock balancer on it?
 
M

Methuselah

New member
I think I can get this one right.

The harmonic balancer dampens torsional forces that can cause stress to the crank bearings. It is not actually responsible for balancing the rotating assembly in any way.

Although Ive never read where this is recommended, often people will remove the balancers as a sort of last step to removing extra rotational mass from the assembly. Once again, I would never do this, it's just an option for racing-only vehicles.
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vortecfiero

vortecfiero

New member
i made the switch from an early internal 4.3 to a later external 4.3
and the harmonic balancer is actually balenced differently
I think its the small chrome plug (about 1/4 x 1/2) in the back of the ring on the balencer moves to a diff hole
from what ive read, they are the same as the passenger car v8 external
and also, V6s dont have as much torsional/harnonic twist along the crank because they are not as long

i would'nt run with out the proper balancer since street engines run in a wide varing range of RPMs and loads
 
4C FED

4C FED

Absolutum Dominium
OK, so I've read this thread and here is my question;

If I had a motor being built/balanced, should I have sent the flexplate along to have it balanced with everything else?
 
ed hess

ed hess

race or get outta the way
ya know i would swear that mama moved better before the black and white chick started swingin her six in that sig.

ed
 
4C FED

4C FED

Absolutum Dominium
ed hess said:
ya know i would swear that mama moved better before the black and white chick started swingin her six in that sig.

ed
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I slowed down the pendulous motion so you could enjoy it more. :D
 
R

rarebit

New member
i have another question for you all- if i had my entire rotating assembly balanced with the stock syclone harmonic balancer and then i later installed a fluidampr for internally balanced v6, would something be wrong now? it seems to be running as smooth as the stock balancer. should i stick the stock balancer back on?
 
M

Methuselah

New member
rarebit said:
i have another question for you all- if i had my entire rotating assembly balanced with the stock syclone harmonic balancer and then i later installed a fluidampr for internally balanced v6, would something be wrong now? it seems to be running as smooth as the stock balancer. should i stick the stock balancer back on?
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I think someone mentioned that the dampners are different between model years.

Even if that is the case, the nature of the dampner is to dampen torsional forces that are specific to the geometry of the 4.3L 90* V6...so I think any dampner for that engine does about the same thing. Some may be more rpm-independent though.
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