06-23-2011 11:57 AM #1
Distributor drive gear for SBC with factory roller cam
I have a late 80's SBC with a factory roller cam and I want to replace the HEI, does this cam require a specific drive gear? I do not know if the current HEI was original or not, does anyone know where I can find HEI distributor part number listings to see what year the distributor is? I know some roller cams require specific drive gear materials/metals.
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That's the same engine I have, 92 with a roller cam, you need to get a bronze distributer gear. I got mine from Summit.
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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?
I believe it's that a roller cam is harder than a standard cam and you can have galling when two rotating surfaces are of similar hardness, one must be softer that's why you need a bronze gear. I don't know this for sure just guessing. It may be more of an issue in high performance engines where RPM will be much higher than a stock 350.
DON must of been sleeping in class again or never did read any thing i posted on this before stock GM steel core roller cam you can use a melodized iron gear or any oem cam steel core heat treaded to stock specs.steel non oem then bronze .two part steel core with iron gear then any grear . iron core roller any gear. i save the bronze gears for race steel cam cores as some of the gears do not have much hold out with big oil pumps .the red bronze grears seamed to work better.all iron gears on msd will work on stock oem type steel cores. if you run a older stock iron dist gear with a oem roller cam you can wear teeth off dist gear or cam or both
Last edited by pat mccarthy; 06-24-2011 at 05:14 AM.