[Fot] Broken Cranks: Was - Any connection between these problems?

[Norlin Engineering]

Interesting to read this thread as I suffered a broken crank on my 1296
engine this past weekend.

This is a small crank engine, prepared to SCCA limited prep rules for HP.
Shift point is 6800-7000 and max revs are about 7500, so the engine is
really not stressed that much.  The crank was balanced, but not nitrided or
shot peened.

The crank broke between the #1 con rod journal and the #1 main journal which
is totally weird.  It's hard to tell looking at the two halves since they
beat on each other for a few seconds before I could kill the motor, but if I
had to guess, there was a fairly large internal flaw in the forging that
didn't show up on the magnaflux test.

I've been lead to believe that these cranks are virtually bullet proof, but
now I'm not so sure.  How many others have suffered broken 1300 crankshafts?

The real bummer in this (besides the cost) is that I was leading HP in the
National when the crank failed.

"Helping to restore the economy thru racing" - Jim Norlin