The concern with any metal timing gears and chain is harmonics and spark scatter.....If you're keying in on this as a problem, and want the best, then go to a belt drive. Many will buy the double rollers, and probably never run the engine hard enough for it to matter. A quality single chain and gears is just fine for a street machine in about 90% of cases.... In the case of the sbc, then if it's really a concern, go to the belt drive and the front mount distributor, spend the big bucks and have the best!!!!