April '21

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40 THE SHOP APRIL 2021 Another go-round building a tried- and-true Gen 1 small-block Chevy. Back to Basics By Mike Mavrigian Part IV EDITOR'S NOTE: This is the fourth article in a multi-part series detailing the build of a 422-ci small-block Chevrolet Gen 1 engine. Part I appeared in the July 2020 issue of THE SHOP magazine, Part II in the October 2020 issue and Part III in the January 2021 issue. ROLLER LIFTERS Since roller lifters feature roller bearings that contact the cam lobes, it is absolutely critical that the roller remains in plane so that the roller bearings glide over the lobes. If the lifter is allowed to rotate within its bore, the roller bearing will contact the lobe at an angle that will quickly result in damage to the lifter and cam. For this build, I selected a set of Morel solid roller lifters that are bridged together with a pivoting link bar. The lifter pair (each pair features an intake and an exhaust lifter) simply drops into the lifter bores, with no custom machining or use of separate guide plates required. Lifter bore clearance is critical in order to maintain proper operating clearance and lubrication. The lifter manu- facturer will specify the correct oil clearance, as it can vary depending on the maker and the design of the lifters. However, a general rule of thumb is to obtain about 0.0015-inch oil clearance. Our Dar t SHP Pro iron block is intended for 0.904-inch diameter lifters, which also must be 0.300-inch taller than stock GM roller lifters. In our Dart block, the lifter bores initially measured 0.9025-inch. Our Morel solid roller lifters measured 0.903-inch in diameter. Our lifter bores were machined at 0.9045- inch, in order to provide a 0.0015-inch oil clearance. This was accomplished on a CNC machining center, verifying that all lifter bores were not only sized to the desired diameter, but that all bores were accurately centered. APRIL 2021 Engine Products p.48 40 THE SHOP APRIL 2021 Our solid roller lifters are Morel's new Black Mambas. Diameter is 0.903- inch. Roller wheels are 0.810-inch in diameter. The increased body diam- eter provides additional stability.

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