Ryan checks crank endplay with a dial indicator. It should be between 0.0004 and 0.0008-inch, with a maximum of 0.0012-inch. This is especially important with a manual transmission where thrust loads vary. | 
Always install screw-in oil-galley plugs. Ford used press-in plugs originally. This is a good engine life insurance policy. | 
Power and reliability come from getting all the tolerances correct. Piston-ring end gapping, for example, determines cylinder sealing and internal friction. The better the cylinders are sealed, the more heat energy can be put to work. |
The Mock-Up
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.
During our mock-up, we learned that our Boss 302 block exhibited incorrect deck height and deck warpage. Eric Peart sets up the block for milling to correct warpage and piston deck height. | 
Mock-up includes installing Nos. 1, 3, and 5 main bearings with lubrication. | 
Jim checks piston deck height with a dial indicator during mock-up. It determines piston depth in the bore at top dead center. Most machine shops do one bore. You should check all of them. Ideally, you want identical deck height on all bores. Record it on each cylinder. |
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-0.0004 to 0.0008-inch. Maximum limit is 0.0012-inch. Connecting-rod side clearances should be 0.0008 to 0.0015-inch. Maximum allowable is 0.0026-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.