Engine balance

    Have read all the searches I can find and would appreciate some clarification.

    The Ford small block is externaly balanced - yes.

    The HiPo is balanced differently to other 289's. I gather early engines had a 28oz imbalance, later engines 50oz and HiPo 30.4oz.

    Ok so how does this work ?

    Is the crank is neutraly balanced ???

    Does the damper have an imbalance of 24.5oz ?

    Does the hatchet have an imbalance of 5.9oz ? making the two total 30.4oz.

    How is the flywheel balanced does that have a 30.4 oz imbalance ?


    If all of the above is correct does fitting the pistons and rods bring the whole lot back into balance ?

    Or am I wrong ? If so could someone explain.

    Thanks

    As you correctly state, the Ford 289 small block is externally balanced. This simply means that when the small block was designed, there was not enough space for sufficient weight on the crankshaft counterweights to balance all of the mass of the reciprocating parts (rods, pistons & rings). So they have to take care of the remaining imbalance on the flywheel, harmonic balancer and the hatchet. Therefore, an originally built motor must be balanced with the crankshaft, flywheel and harmonic balancer assembled together on the balancer machine.


    Sorry, I do not know the proportions of the imbalance between the damper, hatchet and flywheel that you've listed. I'm not sure it matters to the guy doing your balancing as long as you make sure you've physically got correct and original parts. Bob mentions those numbers here (presume you've read this article?) : http://www.fordsmallblock.com/PDF/SmallBlockV8Balancing.pdf


    Your last point is correct - fitting the pistons, rods and rings brings the whole lot back into balance.


    I see you're in the UK. I recently had a 289 motor balanced by Steve Smith of Vibration Free (near Bicester) and from driving the new motor, it was an excellent job. He has balanced many Ford 289 motors (HIPO and non HIPO) and I would recommend him.


    Hope that is some help.

    Sam

    Thanks for the info. I see in Bobs article that he says that the crank is statically in balance and has no heavy side. I can now understand how it all works.

    I want to get the engine balance checked and was not happy to take the stuff to a machine shop without knowing the theory behind it.

    Cheers

    Mark

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