October '20

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34 THE SHOP OCTOBER 2020 OCTOBER 2020 3D Pistons p.42 Engine Products p.46 Install the upper main bearing to the block's saddle, install the lower bearing to the main cap, and install and fully torque the main cap. Adjust a bore gauge to match the journal's diameter. Place the bore gauge onto the installed bearings and note the difference. In our case, the main journals measured 2.4500 inches. With our micrometer set at 2.4500 inches, a bore gauge was set up to that distance, zeroing the gauge to provide our reference. Inserting the bore gauge to the installed main bearings showed a difference (from our gauge zero) of 0.0025-inch greater than zero, indicating that our oil clearance was 0.0025 inch. Follow the same procedure for the rod bearings by installing the rod bearings to the rod and rod cap and fully torqueing the rod bolts. In our case, our crankshaft's rod journals measured 2.100 inches. Initial checking with MAHLE Clevite CB663HN standard upper and lower bear- ings revealed an oil clearance of 0.002 inch. I prefer to allow a slightly looser rod bearing clearance, so I ended up using a mix of a standard bearing shell in the upper location and an X bearing shell in the lower posi- tion, MAHLE Clevite CB663HXN, which provided an oil clearance of 0.0025 inch. While novice assemblers may argue, there's nothing wrong with mixing stan- dard thickness and X undersize bearings on the same rod. By using a standard bearing mated with an X bearing, you gain 0.0005 Another go-round building a tried- and-true Gen 1 small-block Chevy. Back to Basics By Mike Mavrigian EDITOR'S NOTE: This is the second in a multi-part series of articles detailing the build of a 422-ci small-block Chevrolet Gen 1 engine. Part I appeared in the July 2020 issue of THE SHOP. CAM & BEARINGS It's important to note that the small- block format Dart SHP Pro Iron block features a big-block Chevrolet cam bore. The correct cam bearings are provided with the block, Dart P/N 32210010 (2.120-inch). All five cam bearings are the same size, so there is no specific bore loca- tion requirement, as all cam journals are the same diameter. These bearings are anti-friction-coated and feature three oil holes and a continuous oil groove on the outside diameter. When installed, make sure that one of the bearing oil holes aligns with the oil feed hole at the upper main saddles. With the bearings installed, the cam is inserted to verify fit, with our cam rolling effortlessly like hot butter. After the cam is gently removed, all cam journals and lobes are liberally coated with Royal Purple Max Tuff assembly lube and reinserted. BEARING CLEARANCE While the use of Plastigauge may be con- venient, this does not provide extremely accurate readings. In order to obtain a much more accurate clearance measure- ment, measure the journal diameter with a calibrated micrometer and record that dimension. 34 THE SHOP OCTOBER 2020 Part II Our camshaft of choice for this build is COMP's billet roller, P/N 12-000-11. Lobe lift is 0.432 inch at intake and 0.430 inch at exhaust. With our use of 1.6:1 Jesel roller rockers, our effective valve lift is 0.648 inch intake and 0.645 inch exhaust.

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