The role of a woodruff key
 

When assembling my 428 several years ago I noticed the woodruff key located on the crank snout to not be in perfect shape. It was fine for locating the crank gear and harmonic balancer; but the level of engagement (depth into the gear and balancer) was not as good as it could have been. At the time, I researched it and found that the primary role of the woodruff key is to properly locate the gear and balancer on the crank snout. While the compressive force applied by properly torqing the balancer bolt is what actually holds these pieces in place when the engine is running.

Motor is running fine but this is still in the back of my mind. Does the woodruff key play a role in keeping the crank gear and balancer in place when the engine is running? I've got another key but don't want to go back into the motor if I don't have to. And yes, I should have just put a new one in at assembly. But..........I didn't.

Thanks in advance.

Your fine just the way you are but should you ever step up to a solid roller cam and the necessary spring pressures needed for that I would then for certain replace the crank key.

The explanation of the woodruff key's purpose is mostly correct. In the case of a Pontiac, the compressive pre-load applied by the crankshaft bolt holds the assembly in place. The 160 ft. lb. torque spec. Pontiac's use should be considered a minimum. I torque that bolt with a locktite product to 180 ft. lb. torque to be certain that bolt always has pre-load on it. The reason I said "mostly correct" is millions of harmonic balancers are retained to the crankshaft by a press fit only, no bolt or fastener at all. Vintage small block Chevy engines would be an example. The best possible retention method is a combination light press fit, combined with a fastener and a high pre-load. I would check the torque on your Pontiac bolt. If it's staying tight, you are good.

Thank you. Great feedback.

mgarblik is correct, The bolt is what technically holds the balancer in place, the amount of retainment by the key prevents any rotational movement during tightening, and also for proper alignment for crank position reference (timing mark).

ARP replacement bolt torque I think have a value of 220ftlbs, but I would suggest that value to be used only with a forged crank, even though I suspect an OE crank would handle it.

Since we're on the topic, one 'hack' I use (and others) is to dress the nose of the key to allow any slight alignment mismatch between the key and the balancer notch during assembly. I dress the end of the groove on the balancer too.

I also make a sharpie mark on the face of the crank snout that shows the key clocking. You can even shine a light through the balancer groove and see if it's lining up if during assembly you want to be sure. (some take a punch and make a small dot)

Might not be as much an issue with OE cranks & balancers, but the interference fit of aftermarket cranks & SFI balancers can sometimes be a challenge. Since some take considerable effort to install with an interference fit, a puller/installer is required. And you may not notice it's going on 'crooked'. (ask me how I know)


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I replace keys on builds as SOP, and always check the fitment, in both crank and balancer.



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I like the mod to the nose of the key. That would be helpful especially with and ATI and other press fit balancers

Yeah, ATIs are a tight fit, Powerbond ones too. Those Romax ones you had to hone-to-fit as well.

I had a Powerbond I was re-installing, thought I could do it without dressing the key, it turned slightly as I cranked on the installer, and dug a groove into the balancer.

That's happened twice to me, both times were while the engine was in a car. Not sure if that had anything to do with it or not, but I dress them all now. Couldn't tell it was getting harder to turn until it was too late. That was kind of recent, the one before was like 20+ years ago.


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