Mr. mean buzzin half dozen aka hank,
NOOOO, I have never broken a single Ford 300 crankshaft in any of my seven 300-powered hot rods in thirty-some years of racing. I would not characterize the 300 crankshaft as being "weak". Have I ever seen a cracked one - yes. But I have also seen 292 Chevy crank pieces scattered all over the pavement and 292 Chevy blocks cylinder walls split apart like hot weenies. So do I characterize 292s as having weak cranks and potatoe chip fragile blocks? Maybe yes - maybe no.
Any engine component subjected to higher stresses than production is likely to have its cyclical lifespan shortened. A savy engine builder will recognize this and plan accordingly. That is why my street hot rods use stock 300 cranks, my mild (11 sec.) bracket bomber uses a stock crank with a little extra bearing clearance, but my 8-second altered uses the optional Ford forged steel crank, reground with smaller journals, lightened, nitrided, polished, etc., etc. That just makes good sense.
To compare the 300 crank, with its 3.9800" stroke to 200 and 250 sixes is a bit misleading, wouldn't you say? I've got to believe you know enough about engine design to recognize that a crankshaft with a shorter stroke will have more rod-journal-to-main-journal overlap and will thus be less susceptible to torsional fatigue than a crank with a longer stroke.
If you still want to characterize the 300 crankshaft as being weak, well, its a free country. Knock yourself out.
'Scuse me while I go assemble another 300 hot rod motor.
