I've been running standard pulleys up to 7200 RPM without any problems. As long as your brackets are sturdy and the pulleys are lined up correctly you shouldn't have any problems.

I've seen OEM ones crack also FTM. Freddie's fix is the way to go. Relieve the center out about 0.005 to 0.010 and leave about a 1/4" clamp area margin around the perimeter. You can sometimes hear a cracked one. It will click sometimes.

Freddie, can a billet aluminium or steel one be made to mimic the original deep groove 3 pulley part? I guess it would need some testing.....although it looks like the other products including the OE pulleys where never really tested!

Also (and I think someone has already pointed this out) surely GM knew about this and put out a better pulley on later Hi- Perf big blocks.....like LS6 454?

I guess when they stopped using the short water pump they no longer used cast iron pulleys. As far as I know all of the pulleys for the long water pump were steel.

Looks like 3921923 Crank Pulley is listed for all big blocks that used the deep groove.. L72, L78, L89, LS6. This could be in correct, as it's info I got off the web...:dunno: