Butler Performance Pre-Assembly Tip Page

The pre-assembly mock-up of an engine to assure its proper fit, clearance, and alignment is essential to any correctly built engine.

***THE ENGINE BUILDER must check for any defects in material or manufacturing PRIOR TO INSTALLATION/ASSEMBLY. It is the final responsibility of the engine builder to do this inspection. If a defect is found the part must be returned to Butler Performance immediately***

The engine bearing oil clearance must be checked. If necessary, the oil clearance can usually be adjusted by the use of special bearings designed for this purpose.

The rod and main bearings, and the connecting rods must be inspected to be sure they clear the enlarged journal fillet radius on the special made crankshafts. The bearings and connecting rods may require chamfering to clear this radius.

The piston to counterweight clearance must be checked with the crankshaft installed in a block. The piston must clear by approximately .050”. Also, check the clearance between the counterweights & block and the connecting rods & block. Piston to valve clearance should also be checked before assembly.

 Rings must be File Fit. “Drop in” sets should be checked also. Check ALL rings in set, including oil rails and rails for gapless rings if included.

 The oil passages must be inspected to be sure they properly intersect to provide full oil flow without any restriction. THESE PASSAGES MUST ALSO BE CLEANED THOROUGHLY WITH A BRUSH, first using solvent and then with hot, soapy water to remove any dirt or debris.

 The installation of such items as the timing gear, pilot bushing, & flywheel should be checked to discover any possible problem before the entire engine is together and the parts cannot easily be corrected.

 Improperly aligned bellhousing, transmission, or too long a pilot shaft can cause the main thrust bearing to fail. This alignment must be checked and corrected with offset dowel pins if necessary. If the pilot shaft “bottoms” in the crankshaft, the pilot shaft must be shortened. Often, the pilot hole cannot be made deeper without intersecting the oil passage within the rear main. THE THRUST END PLAY SHOULD BE CHECKED BEFORE AND AFTER THE TRANSMISSION IS INSTALLED TO BE SURE THAT NOTHING IS WRONG AND THAT THE END PLAY REMAINS THE SAME.

 The oiling system must be primed before attempting to start the engine for the first time. The priming can be accomplished on a wet sump system by placing a shaft down the distributor hole and turning the oil pump over with a drill motor. We offer a Pontiac oil pump primer shaft part # BPI-039P for $19.00 On a dry sump engine, the drive belt is removed and the engine is primed by turning the external dry sump oil pump over with a drill motor.



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