Amen to that-

Posted by Bob Carabbio on March 10, 1998 at 10:51:19

In Reply to: Re: counterweight crank
posted by Joel Rapose on March 10, 1998 at 09:37:05

As Joel says, the "A" should be pretty smooth and quiet at speed, and the faster you go the quieter it gets. the vibration more typically is worst during deceleration.
Properly assembled, the stock "A" engine is balanced both dynamically (as well as any vertical four can be balanced) and statically.
Counterbalances don't improve either the static or dynamic balance of the engine, EXCEPT THAT they serve to prevent bending of the crankshaft at speed, counteracting the pull of the 1 and 4 throws against the 2 and 3 throws.This prevents the destruction of the center main at elevated speeds (which is the reason I'm C'balancing).A vibration that grows in intensity with increasing speed is probably due to something else.If the flywheel is out of balance, wobbles, or (shudder) is loose (it happens!), no amount of balancing will do much for you.It would be best to find the root cause before employing extreme methods to mask it.
Counterweights (4) are welded, and sometimes also bolted also(per Ron Kelley)to the four circular plates on the crank 180 degrees from the corresponding rod throw.One by #1 main , two by #2 main and one by the rear main. the crank (which should have been Magnafluxed for cracks before any work is done)is then straightened (if necessary) and re-ground for absolute concentricity of all the mains.
Any crank balancing should be done with the flywheel and clutch plate mounted and torqued.
Bob Carabbio

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