flywheel on a balanced engine

[Jack O.]

Hopefully some of you remember my earlier posts concerning the problems I've been having with my dual disk (MA6) clutch. To review, I have a '69 427 that's been fitted with a dual disk clutch. However, the setup appears to be for a 454 since the clutch is for a fine spline trans (which the car now has) and the flywheel has the extra casting material used for an externally balanced engine. BUT the flywheel also has been drilled extensively to remove material. Finally, my questions:
- Is drilling the flywheel in this manner typically done by a machine shop to balance an engine? If so, does this prevent me from being able to replace the flywheel with a standard 427 flywheel since it would throw off the balance?
- Is it possible this was done to neutralize the flywheel (as far as balancing goes) since it's a 427 which is not externally balanced?
- Can a machine shop check the balance of a flywheel as a stand alone piece to tell if it's neutrally balanced?
Thanks for the help.

[Clem Z.]

Re: flywheel on a balanced engine

a good machine shop that does balancing can put the flywheel on a mandrel in a balance machine and check to see if it is neutral balance

[Joe L.]

Re: flywheel on a balanced engine

Jack------

You can change to a standard, neutral-balanced flywheel with no problem assuming that you're certain that the engine is a 427. However, I'd recommend having said flywheel and pressure plate assembly, even if new, checked for proper balance prior to installation.

[Jack O.]

Re: flywheel on a balanced engine

Thanks Joe. What about if the flywheel was balanced in a specific way in order to balance the engine? Is that ever done and wouldn't that prevent me from changing since the new flywheel would have to be balanced exactly like the current one?
Thanks.

[Clem Z.]

Re: flywheel on a balanced engine

a good shop can duplicate the balance of your present flywheel

[Chuck S.]

Re: flywheel on a balanced engine

I don't know about any special considerations of Chevy big blocks, but maybe the following will be helpful in understanding the engine balancing process.

When I had my small block balanced during rebuild, engine balancing was explained to me this way: The major components of the engine are balanced individually beginning with the dynamic balancing of the crankshaft. If necessary, the crank counterweights are drilled to remove material, or in some cases to add "heavy metal" to perfectly balance the crankshaft.

The rotating assembly is then built up and re-balanced with each new addition by making balance adjustments to each new component (flywheel, clutch assembly). Pistons and connecting rod assemblies are all adjusted exactly to the lightest weight of the set. The end result is that a component can be replaced without affecting the balance of the engine by having the new component, a new pressure plate assembly for example, dynamically balanced before installation.

Of course, if an engine was not balanced to begin with, balancing a new component won't improve the engine's balance, nor will it make it worse.

[Chuck S.]

Additional Comment

To my knowledge, there is no way that you can KNOW FOR SURE an engine is balanced without tearing it down and checking each components balance. A previous owner can tell you that he paid to have it balanced, or he believes it was balanced, and you can take that for what it's worth.

If an engine is externally balanced using the flywheel (454s?), it will be dangerous to assume that you can replace the flywheel with a balanced flywheel. That is why Clem is recommending you have a machine shop balance the new flywheel to the same specs as the old one. When they put your old flywheel on the balance machine, they will know immediately if your engine has been internally balanced: If the engine has been balanced, then the flywheel will also be balanced. If the balance is way out of whack, then that unbalance is probably compensating for internal unbalance in the engine.

[Jack O.]

Re: flywheel on a balanced engine

Thanks to everyone for the helpful comments and suggestions. I'm taking the flywheel into the machine shop tomorrow to check the balance. Hopefully, as I suspect, it was drilled to neutral balance which will allow me to go back to a stock flywheel and clutch.

[Joe L.]

Re: flywheel on a balanced engine

Jack-----

The others have answered the question. In an internally balanced engine, if each of the components of the reciprocating assembly are seperately neutral-balanced, the complete assembly will be neutral-balanced. This is exactly how the GM engine plants did it for most engines.