Flywheel balance

[Bill Bayard]

Most engine balancing jobs go from the harmonic balancer back to the flywheel,
but some people lighten their flywheel by drilling and then rebalancing.
How much of a negative effect will a flywheel
have, if it is balanced separately from the
rotating assembly? If this will be a problem,
what is the best way of dealing with it,
short of tearing the engine apart and starting over(not my preferred option)?
Expert suggestions, hints, ideas, help will be greatly appreciated.

Bill

[ March 01, 2002: Message edited by: Bill Bayard ]

 

[Bill Bayard]

Dick,

The car finally made it to the right side
of the Pacific, and is winging it's way to Washington, D.C., then on to Baltimore by truck tomorrow. It won't clear customs until
Tuesday or Wednesday, depending on whether they search it, or just release it. They might be looking for refugee kangaroos! Who knows?
I've given up on expecting it to be on time. If by some miracle, it is, I would
be pleasantly surprised. Just so long as
it gets here in one piece!

Bill

 

[Robert Logan]

Bill,

There is a major difference between Ford and Chevy in the way that they are ballanced.

The Chevy components are all balanced 'nuterally' , that is the flywheel, the crank complete with con rod and piston and the harmonic balancer are all balanced seperately and to ZERO.

The Ford is balanced together, that is that all the components are balanced as one. This is the reason for the HARD connections for the flywheel (offset bolt) and the harmonic balancer (keyed). This ensures that they are only fitted in one place.

If you want to replace the flywheel on your Ford than the replacement flywheel must have the same out of balance force as the old flywheel or else the WHOLE rotating assembly must be reballanced.

As regards to lightening the flywheel, this is usually done to reduce 'Inertia' which is the opposition to acceleration. The formula for Inertia is : I = mk2 (squared)

where m = mass
k = radius of giration

The radius of giration is an imagionary infinately thin disc where the whols mass acts through ( 0.7 radius for a solid disc)

As the majority of GT40 replicas use a smaller flywheel the 'k' is already reduced and as this is the dominant factor (it is squared) than there is realy no reason to lighten the flywheel. A major disadvantage of reducing the Inertia too much is that the car has problems ticking over.

Again please consider all ramifications of your actions and remember that this engine design is a fine science.

Best wishes to all,

Robert

 

Hi Bill

I had to balance my fly-wheel without striping my engine. The way I did this was to
use a Ford crank, rod, piston, harmonic damper and fly-wheel from another Ford
Windsor V8 with the same counter balance as my engine. Usually 28oz counter
balance and then the engine shop added weight to put this assembly into balance.
Once this was achieved, the fly-wheel was removed and my billet steel fly-wheel
(neutral balance) was bolted in place. Then weight was added to the back of the new
fly-wheel, I think around 70 grams, with fine tuning being done by drilling lightening
holes on the opposite side to achieve true balance.

I installed the new fly-wheel and found that the engine ran smoothly with no vibration.
However if you can use the parts from you own engine it has to be the best way to go.

Chris

 

BILL HAVE YOU GOT THE CAR YET