Damaged woodriff key slot on '66 L79 crankshaft - NCRS Discussion Boards

Damaged woodriff key slot on '66 L79 crankshaft

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  • Bill P.
    Infrequent User
    • January 4, 2022
    • 5

    Damaged woodriff key slot on '66 L79 crankshaft

    While working on my 66 L79 I noticed that the harmonic balancer and crank pulley were wobbling. I removed the balancer. I found the problem. 1) It had the incorrect harmonic balancer installed. Looks like it is for the 300 HP engine. 2) somehow the woodruff key was sheared, damaging the crankshaft key slot and cracking the balancer hub. It looks like the snout on the crank was damaged as well. It looks a little worn. Looks like I'm pulling the engine.
    Does anyone have experience with this?
    Can the crankshaft be repaired?
    If not, does anyone know where I can find a good 4577 crankshaft? I know that I want to stay away from a crank that was reconditioned more than 0.010 under because of the Tufftriding surface hardening treatment.
    Is the 2680 crank a good alternative?
    Is there a good aftermarket option?
    Thanks for any input.
    Last edited by Bill P.; October 8, 2025, 01:47 PM.
  • Tom P.
    Extremely Frequent Poster
    • April 1, 1980
    • 1826

    #2
    Yes, as a matter fact I have had this happen.
    One day I noticed the balancer on the SB400 in the 56 was slightly moving back and forth. Upon removing the balancer I discovered the keyway on the crank snout was enlarged, the key was damaged and the keyway in the hub of the balancer was enlarged. I discussed this with my machinist and he recommended that on future engine builds to have the crankshaft keyway broached FULL length and use a full length key.
    I contacted Damper Doctor and sent the balancer to them to have the balancer rebuilt, rotate the hub/ring and broach a new keyway.
    100_2121.jpg

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