A mock-up can save a lot of grief when it's time for assembly and fire up. Mocking-up an engine early on establishes dimensions, enabling you to correct irregularities before final assembly.
A mock-up involves temporarily assembling the engine-crankshaft, bearings, pistons, and connecting rods-to measure tolerances. It should also include installing the cam and heads to check piston-to-valve clearances. To be absolutely certain of every aspect of an engine build, you need to check everything, including: Short-block preassembly one cylinder bore at a time to check deck and compression height. Do this without installing piston rings. Rod and crank-to-block clearances.Minimum clearance allowed is 0.060-inch. Parts grow when they get hot. Piston-to-crank counterweight clearances; a 0.060-inch minimum. Crankshaft endplay-0.004 to 0.008-inch. Maximum limit is 0.012-inch. Connecting-rod side clearances should be 0.010 to 0.020-inch. Maximum allowable is 0.023-inch. Check again during final assembly. Piston-to-cylinder wall clearances. Piston ring and groove dimensions, including ring-side clearances. CC valve reliefs to check valve-relief volume. Ring end-gap clearances. Main- and rod-bearing clearances. Thrust-bearing and width clearances. Install the oil pump to determine pump-to-crankshaft counterweight clearances; no less than 0.060-inch. Oil pump rotor-to-housing clearances. Check for smooth operation by hand once the pump cavity has been oiled. Piston-to-valve clearances on all cylinderbores. Valve stem-to-guide clearances and movement. Valves should glide smoothly through guides. Check stem and guide widths. Spring compression and pressure. When installing heads for mock-up, use a head gasket but don't torque. Measure (cc) chambers to determine volume. Record the numbers. Intake manifold for proper fit without a gasket.