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Guys,

Can somebody please explain to me the basics of crankshaft balancing?? The reason I ask is I want to buy a manual transmission flywheel but am unsure what type is required for my 393 stroker. Additionally are there any significant power gains to be had in using an aluminium flywheel over a steel flywheel in cobra replica used for street driving?

Cheers,
Martyn
 

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crank balancing:

Machinest will take the rods, weigh the big ends and remove material from the them so that they all are the same weight as the lightest one. Same for the small end. Then, they weigh the pistons, find the lightest one, and match the rest to that one. Then, they will take the weight of a piston, rod, bearing, ring pack, circlips and weigh it all...then depending on what factor they use, they will make a bobweight that's the same weight. The bobweight is like a specific weight clamp that clamps onto the crankshaft rod journal...and when all 4 of them are installed (along with the balancer and flexplate/flyhweel) the crank is spun in a special machine. The machine tells where and how much material needs to be removed or added in order to get it within a specification. Removing material is easy via drilling a counterweight. Adding material usually means drilling the side of a counterweight and adding a slug of metal that's heavier than what was removed....usually "Mallory" or "heavy" metal..then it has to be welded onto the crank (to be done right...I've seen shops that didn't weld them before, and it works, but it can come out...which ain't exactly pretty). Why do you want it balanced? Because you don't want it to vibrate...vibration causes wear, cracks, and all sorts of problems.

on a 393, yeah, I wouldn't be afraid of using an aluminum flywheel. The crank weighs a ton as it is (those 3" mains don't lend themselves to light weight) and anything you can do to lighten it up will make it more responsive. If you can use light pistons and I beam rods, you'll be surprised how responsive such a "big" engine can be. As far as power gains, I'm not sure it would gain any power as far as HP numbers, but I'm sure you'd most definetly feel the difference in the seat of your pants, and that's where it's important!
 
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