This is an interesting subject to me because I have never fully understood it. The Vortec Chevy engine (1999) I had in my 23, and the SBF engine (1992) in my current 27 are both roller cam engines, and in both cases I used an aftermarket HEI distributor. The one in the 23 was a ProCharger (I think that is the name) and the one in my 27 is a Mallory Unilite. I don't know if either had the bronze gear that is "required" for roller cam engines, but occasionally I would pull the distributor out and never noted any odd wear or problems.

So the question is, what makes a roller cam distributor drive gear different from one on a flat tappet camshaft that makes it necessary to use the bronze gear? Are roller cams made from a different steel, or just the drive gear?

Don