THE SHOP

April '19

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38 THE SHOP APRIL 2019 PRECISION ENGINE The knobs are offered with either 1/4-inch- by-20 or 5/16-inch-by-18 female threads. Granted, these knobs are intended for air cleaner lid use and may appear a bit large in diameter for valve cover use, but they're extremely functional, adding a bit of convenience for hand-servicing the valve covers. While this setup may be totally unnecessary, I thought it looked cool, and the quick no-tool servicing would definitely come in handy in the pits. In order to provide an oil-fill location, I installed a Jones Racing weld-in -12 female bung to the roof of the left-side valve cover to serve as an oil fill port. This is sealed with a Jones Racing screw-in aluminum plug that features an OD hex and a sealing O-ring. Since we're using the Jones Racing vacuum pump system, the engine needs to be sealed, so a valve cover breather was a no-no. Installing the bung required cut- ting a 1-5/8-inch hole in the cover (8-7/8 inches from the front wall, in line with the second pair of valve cover bolt locations, in an area where I knew I'd have a clear shot for oil fill between rocker arm locations). In addition, a -12 weld-in male fitting was needed on the front wall of each valve cover in order to plumb to the Jones Racing vacuum pump. For each valve cover, a 3/4- inch hole was drilled and the male weld-on fitting was surface-mounted to the valve cover wall and TIG welded around the perimeter of the fitting's hex. Saeco, a local fab shop in nearby Wad- sworth, Ohio, performed the TIG welding of all three fittings (since yours truly doesn't own a TIG, and doesn't know how to use it even if he had one). VACUUM PUMP Jones Racing supplied a vacuum pump system featuring its lightweight billet alu- minum vacuum pump VP-9100C. This is a two-stage, gear-style vacuum pump that runs at 50-percent of engine speed and pulls a constant 15 psi, providing enhanced piston ring seal. The negative pressure created by the pump results in less resistance on the pis- tons during the compression downstroke, resulting in faster piston acceleration. This constant vacuum also helps to draw para- sitic oil from the rotating assembly (theo- retically increasing power), and allows the oil pump to function with less resistance, which should increase oil flow. I mounted the pump on the lower right engine side. In order to provide clearance for the water pump neck, Jones supplied an extension bracket that shares the two block mounting bolts for the crank trigger sensor bracket. In order to provide a mounting for the crank pulleys (for both our vacuum pump and our Jones Racing alternator), we installed Jones' DH-8101-B BBC drive hub and its DHM-8101-B (3.500-by- 1.125-inches OD) mandrel. The drive hub (and the hollow mandrel) secure to the crank snout with a 1/2-inch- by-20-by-6-inch bolt. In addition, to prevent the drive hub from rotating independently, the hub features two 3/16-inch roll pins. This required drilling a pair of 0.190-inch holes in the face of the damper (on the recessed flat face that surrounds the crank snout). The roll pins were pressed into the drive hub and the roll pins engage into the holes drilled in the damper. The drive hub mandrel threads into the drive hub (featuring a left-hand thread) and features a 1/8-inch keyway slot that runs the entire length of the mandrel. Once I mocked up the crank snout pulley and spacer assembly for proper pulley align- ment to both the alternator and vacuum pump pulleys, I removed the pulleys and spacers. I installed a 0.250-inch-thick spacer against the drive hub, then installed a key for the alternator drive pulley. The alternator drive pulley and its guide plates were slipped on, followed by three aluminum spacer rings (one 3/8-inch and two 1/2-inch-thick spacers), followed by the vacuum pump drive pulley, one 1/2- inch spacer and finally the billet aluminum nose cup, lock washer and the 1/2-inch-by- 20-by-6-inch crank snout bolt. The array of aluminum spacers (in various thicknesses) allows you to tune the spacing of the pul- leys on the mandrel. In order to achieve fine-tuning of the vacuum pump's pulley to the pump's drive pulley on the crank mandrel, by loosening three set screws in the pump's pulley you're able to slide the pulley fore/aft on the pump's shaft for perfect belt alignment. Once alignment is determined, tighten the set screws. Access holes in the pump pulley allow easy entry for a hex wrench for servicing the set screws. Routing the plumbing for the vacuum pump was super simple. I made a pair of -12 hose assemblies using 90-degree -12 hose ends at each end of the two hoses. The two outlet ports on the pump are plumbed directly to the -12 male weld-in fittings on the front face of each valve cover. The single outlet (exhaust) port from the pump will be plumbed to a remote breather in the dyno shop. Assembly of the -AN hoses was straightforward in terms of installing the hose ends to the hoses (I used swivel-type hose ends at the valve cover locations to enable easy clock-position adjustment for a precise hose-end-to-fitting alignment). The only special step involved inserting a section of Jones Racing's flat-wound internal support coil into each hose length. This ensures the stability of the vacuum hose, preventing any potential restriction Building a 632 Mountain Motor I went a bit overboard with plug wire clamps in an effort to nail all of the wires down to prevent them from flopping around. I made two L-brackets that attach to the rear manifold bolts to provide a mounting spot for the four-wire MSD wire dividers.

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