THE SHOP

April '19

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40 THE SHOP APRIL 2019 PRECISION ENGINE In order to handle fuel feed to our mega- displacement carb, I installed a BG P/N 170021 adjustable-length fuel log (adjust- able for bowl inlet match-up), a pair of BG fuel inlet extension fittings P/N 140023 (7/8-by-20-by-minus-8 swivel), a Trick Flow -8 TFS-23001 in-line billet fuel filter, a BG fuel pressure gauge P/N 170124 and Race Pump's fuel pressure regulator P/N 5010. The BG adjustable fuel log is pretty cool. In order to adjust length, simply slide the two ends apart or closer together by hand. One tube slides inside the mating tube, internally sealed with a series of three spe- cial O-rings, so no tools are required to adjust the log tube length. Either end may be used for the fuel inlet (each end features a 3/8-inch NPT female thread), and one end features two 1/8-inch NPT ports to allow mounting a fuel pres- sure gauge on either side (depending on how you orient the log). Install the two extension fittings to the carb, adjust the log length to align to the fittings and install, tightening evenly back and forth between the two fittings to pre- vent binding. The BG pressure gauge is also very neat. It's internally dampened without the use of liquid (since a liquid-filled gauge might be affected by engine heat and lead to inac- curate readings). I plumbed everything using Earl's -8 stainless braided hose. At the fuel pump outlet, I used a 45-degree -8 hose end. At each side of the filter, I used -8 straight hose ends. At the entry of the fuel pres- sure regulator, I used a -8 straight hose end attached to a -8 male to 1/2-inch NPT male adapter (the bottom inlet port of the regulator features a 1/2-inch NPT thread). AIR FILTER Although not needed for the dyno run itself, I opted for a way-cool K&N X-Stream air cleaner assembly, P/N 66-3090. This assembly features a 14-by-5-inch-high round open-element filter in addition to an open-element top. The kit included all mounting hard- ware, including a neoprene base gasket for the Dominator, a chrome steel base, a 5/16-inch-by-18 male to 1/4-inch-by-20 female adapter, a length of 1/4-inch-20 all-thread, two steel washers, one rubber washer and 1/4-inch-by-20 nuts. The only fiddling involved cutting the all-thread to length to accommodate the filter height. Install the 5/16-inch-to-14-inch adapter to the carb and install a 1/4-inch-20 jam nut on the all-thread (against the adapter top). Install a 1/4-inch-20 nyloc locknut onto the all-thread. Install the base gasket, the steel baseplate and the round filter. Lay a straight- edge across the top of the round filter element, and position the top of the nyloc nut three turns below the bottom of the straightedge. Next, remove the all-thread (keep the nyloc nut in place). Mark the all-thread at a point 1.25 inches above the top of the nyloc nut and cut off the excess all-thread at this mark (you want 1.25 inches of thread exposed above the nyloc nut). Deburr and chamfer the cut all-thread. Reinstall the all-thread stud. Place one steel washer on the all-thread, resting the washer onto the top of the nyloc nut. Install the top filter element, making sure that it's seated into the steel baseplate. Install the rubber washer onto the exposed stud, followed by a steel washer and a 1/4- inch -20 nut. K&N supplies a nyloc nut for the top of the stud, but I opted for a burgundy- anodized Top Seal billet aluminum knurled air cleaner lid knob (1/4-inch-20 internal thread) that I obtained from Cam Motion. These knobs (available in short and tall versions) look cool and provide convenient hand-operation for air filter servicing. An O-ring is featured on the underside (seated in a milled groove) to prevent slippage and unwanted loosening. THERMOSTAT HOUSING I installed a blue anodized aluminum ther- mostat housing/intake filler assembly from JEGS, P/N 53012. This features a 1.5-inch- diameter radiator hose connection. The two-piece design allows you to flip the lower housing to orient the hose nipple to either the right or left side of the engine. The lower housing seals to the manifold via our Victor race gasket (aluminum core with silicone seals). The upper neck seals to the main housing with a built-in O-ring seal. An overflow nipple screws into the neck via a 1/8-inch NPT thread. The rear of the main housing features two 1/4-inch NPT and one 3/8-inch NPT female ports, which I sealed off with NPT plugs (these could be used for additional coolant plumbing, gauge or sensor attachment, etc.). For a pressure cap, I chose Moroso's 24-pound race cap, P/N SDC-63324. THE DYNO RUN I transported the engine to Gressman Powersports in Fremont, Ohio (about 90 miles from my shop). After adding 7 quarts of 30-weight oil to the sump, the Building a 632 Mountain Motor OUR FINAL DYNO PULL RPM TORQUE HP 5200 844.4 836.0 5300 846.8 854.5 5400 851.9 875.9 5500 855.8 896.2 5600 860.5 917.5 5700 863.9 937.6 5800 864.2 954.4 5900 863.3 969.8 6000 862.5 985.4 6100 863.7 1003.1 6200 860.1 1015.4 6300 858.5 1029.8 6400 855.5 1042.4 6500 854.0 1056.9 6600 850.5 1068.8 6700 848.0 1081.8 6800 842.5 1090.8 6900 835.9 1098.1 7000 829.5 1107.6 7100 823.0 1115.5 7200 811.4 1112.3 7300 798.1 1109.3 In the 5700 – 6200 RPM range, average Fuel A lb/hr was 174.5. Fuel B lb/hr was 170.9. A/F ratio was 14.79 (max 15.31). Average volumetric efficiency was 113.6%. Image 3 Following a couple of test runs (to perform our pre-flight checks), the air feed stack is installed and we're ready to make our first hard pull.

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