Guys, check out my modified woodruff key ( crank key )

[scouttster]

My Pulley Dilemma-
The pointer is pointing to the damaged key and also a pic of the damage that was done to the harmonic pulley.
I extended the key, hoping to go through the damaged area of the harmonic pulley and bite at the other side of the keyway on the pulley where there is no damage. I'll fill the damage area with epoxy. Not sure if this is going to work. As you can surmise from the damage - half the woodruff key ( aka halfmoon key or crank key ) bites the harmonic pulley and the other half bites the timing sprocket.. That little key takes alot of load / stress... Also, I used 1/4 sheet steel which is soft. Should I just go with it as is or heat and try to temper it a bit to harden it up? I can't locate a used harmoic pulley at a reasonable price - so this is my attempt at a fix-all.. Thanks

[Highlander]

Scouttster- You'll have a hard time trying to harden that soft sheet steel, it's not made to be hardened. The only way to increase its load bearing capacity would be to have it case hardened. You might consider filling the beaten area of the crank pulley with another piece of that same material and bonding it in with something akin to JB weld. OR try using a metal filled epoxy repair system (Preferably not aluminum filled)and trim the repair while its still malleable. I wouldn't trust to the soft steel extended key alone without getting a good solid fill in the pulley (as you were planning). The key itself won't see a lot of stress unless you don't get the pulley bolt torqued down and it loosens (as you've found out). The only load on it is from the ancillaries being driven and the cam (which doesn't create a great deal of load).
If you use an epoxy type filler, be sure that it can withstand the temperatures that it'll see(possibly around 250-300°F). Some epoxies have a Tg below that and they will turn to goo. Good Luck!!

[Petros]

Good job on the modified key. That is an excellent idea. DO NOT harden it, it is supposed to be soft in case of backfire or damage you want to key to fail, not the crank shaft. I also second the suggestion you make a metal shim to fill the gap in the pulley key way, and then use metal filled epoxy to hold it in place. With the front pulley bolt cleaned and properly torqued with the epoxy wet, everything should hold together just fine.

Actually the loads are much larger than just the drive pulleys, the front pulley has a harmonic balancer which means there are high frequency harmonics that come through the crank and are dampened by the rubber ring in the front pulley. You will lower the harmonic loads with a lighter flywheel (which I highly recommend) or a stiffer crank (not easy to accomplish), but it is important that the rubber ring be allowed to damped the harmonic vibration or cracks in the crank can develop.

Actually the operating temp of the front pulley should rarely get above about 200 deg F even at full throttle going up hill (The highest we ever measured in a 900 hp turbocharged full race GTP car was about 210 deg). So any epoxy good for 250 deg F or better should be fine.

[takza]

IMO...the key only locates the pulley on the crank...the torque of the bolt holds it in place. The keys are made of soft iron in order to shear if the bolt gets loose. Though they do hold some since with my 1st t-belt job...the bolt was loose and the key was slightly deformed...caught it just in time.

[scouttster]

Guys, thanks for the input.
Glad to hear the key doesnt take much load and is in fact the properly torqued bolt that holds it all together for the most part.