If your racecar, Corvette, or race Corvette requires a distributor with a mechanical tach drive, these Pro-Billet Tach Drive distributors from MSD are what you need. The MSD 8572 distributor features a race-proven magnetic pickup that delivers precise trigger signals to your MSD ignition every time one of the reluctor's precision paddles pass by. This reluctor assembly is connected to an oversized steel shaft for increased strength and endurance, and is responsible for triggering the magnetic pickup. Inside the stout billet 6061-T6 aluminum housing, a sealed ball bearing and long sintered bushing guide the 0.500 in. steel shaft for high-rpm accuracy. Just above the reluctor is an adjustable mechanical advance assembly that lets you tailor a timing curve to match your engine's needs. This assembly is TIG welded for strength, and features chromoly weights and nylon pads to ensure smooth advance as the rpm increases. Corvette models feature a vacuum advance, and are available with or without an adjustable slip collar for engines that have had the deck height modified or use exotic intake manifolds. The tach drive distributors also feature a Rynite base. The tach drive assembly has a grease fitting for lubrication, is compact to clear the firewall and linkage, and can be repositioned easily to fit different applications. These MSD 8572 distributors require the use of a separate ignition box, such as an MSD 6, 7, 8, or 10 Series ignition.