Like Dave and Hoyt, I too bought a two groove harmonic balancer which was modified by Buffalo (although his given name is Steve, he actually prefers to be known as Buffalo) of Buffalo Enterprises in Arlington, WA. I haven't yet installed this pully on my Chevy 261 engine but here are three tips provided by Buffalo relating to this pully. 1) I (meaning Buffalo) use a speedy sleeve on new pully. 2) It is best to drill and tap the front of the crank so you don't have to beat the damper on with a hammer. 3) If the metal cover front seal retainer is not bolted on yet, drill the cover holes out a little and install the cover with the bolts loose. Press the damper on and use it to center the seal. Then tighten the bolts on the metal cover.
I wanted a dual belt system to allow me to drive an A/C compressor and my alternator without having to have the same belt drive both units. I also wanted to have a two groove water pump pulley (perhaps more for aesthetics) so that one belt would connect the balancer, water pump and A/C compressor and a second belt would connect the balancer, water pump and alternator. The question was, what could I use for the dual groove water pump pulley? Once again, Buffalo came to the rescue by advising me that "all good Chevy engines should have at least one Ford part" and told me to locate a Ford pulley with the casting number, C8AE-8509A. These pulleys were used on Ford 390 and larger engines in the late 60s. Knowing what I needed and locating this part were two entirely different issues. I checked with a couple of large SoCal Ford dealers only to find that the part was "obsolete". I then attempted to locate one at local wrecking yards but found that none had Ford vehicles from the 60s, let alone one with a 390 or larger engine. I then resorted to eBay and, as luck would have it, I found exactly what I needed. This is a 7 inch pulley with the correct offset to match the balancer below. I can't say that it's necessary to run a dual groove water pump pulley, but it sure looks better than the alternative of running one of the belts directly from the balancer and skipping the upper water pump pulley.
