Eagle 4.250 Cast Crank Broken

[Jerry Clayton]

I asked for info on the dampner and I mentioned how driveline harmonics could break a crank at the front----
of the number (probably 30-40) of cranks I've seen broken over the years, could be traced to contributing factors that weren't crankshaft---probably one of the primary reasons a circle track car breaks a crank is that it either hit a wall or possibly a tire to tire with another car a couple of weeks earlier that killed the dampner(especially a fluid dampner)
Wrong flywheel used ( external/internal problem) will break the front as its the weak point.
I've seen a few top fuel/funny cars break center main(usually without center counterweights that strengthen it there)
Seen a few early chrysler 392 types break in the relieve groove at the front journal--a lite hammer tap to ring the crank will show this up--if it rings your good, if it thuds, its cracked.
Crank designers talk about 8 or 9 different orders of vibration?????

The old guys that ran the flat cranks-----

when you see something besides the crank broken, look for another reason----