Genuine 1991 Pontiac Firebird Crankshaft

1991 Pontiac Firebird Crankshaft Parts Questions & Experts Answers

• Q:

  How to install a crankshaft during engine reassembly on 1991 Pontiac Firebird?

  Posted by Timma H.

  A:

  Crankshaft installation is normally one of the first steps in the reassembly of an engine, if the engine block and crankshaft have been washed down, envisaged and restored. Place the engine in a way that the bottom is upward, then, after removing the main bearing cap bolts, take off the caps and place them in the correct orientation for reassembly. If old bearing inserts have been left in the connecting rods, it is necessary to take them out and, with a clean and non-adhesive material, such as a lint-free cloth, clean the main bearing surfaces. Remove and clean the back sides of new main bearing inserts, then install one half of them to each main bearing saddle in the block and make sure the tabs and oil holes locating correctly without use of lubrication. The flanged thrust bearing is required to be fitted in the suitable cap and saddle for the V6 and V8 engines. Scrub the bearing faces and the crankshaft's main bearing journals using cleaning alcohol and look out for dirt in oil holes. Place crankshaft in the correct position with counterweights sideways and then, measure the main bearing oil clearance using Plastigage, when placing it be sure it is parallel to the journal axis and does not block oil holes. Fit the caps in the positions provided and screw the bolts in stages in the center main, then each of the other main bearing caps without rotating the crankshaft. Finally, after the taking off of the caps, and after observing that the crushed Plastigage width corresponded with the scale, ascertain that the oil clearance is within or meets the required standard. If clearance is wrong, check the bearing insert dimensions and also the condition of the surfaces for cleanliness. All of the Plastigage must be cut away and the crankshaft pulled out, bearing surfaces must be free of Plastigage residues and coated with a light film of moly-based grease or engine assembly lube. Grease the rear main oil seal, if necessary, for some engine models, and apply the gasket sealant to the main bearing cap for some engines before laying the crankshaft back in the block. Ensure bearing faces in the caps are free of debris then applied the grease on them before placing the cap with arrow facing forward tighten the bolts to torque in three steps. Turning the crankshaft and feel whether it binds or not, and lastly the final check on the crankshaft end play the use of feeler gauge or dial indicator.

  Answered by GM Parts Specialist Fernando / Jan 13, 2026