I am assembling rebuilt 350. Question on bearing clearance measured w/plastigage- On the main bearing crank and cap the plastigage thickness indicates .003". On the next main the plastigage deformed thickness indicates .002" on the crankshaft surface, but .003" on the inside of the bearing cap. So what is the clearance? .002 or .003? Anyone had this happen before? I torqued the bolts to 70 ft-lbs and immediately removed them and pulled the caps. Not sure what I did wrong if anything.

I have a standard set of bearings and a .001 under set. Some of the crank measurement required .001 under and others standard size. Then there's the ones right at the edge- I could go either way (or maybe I put a .001 under bearing half with a standard size to get .0005" under). First I have to have confidence that the plastigage reading is good before I even start looking at this.

 

From the 92 firebird service manual:

Main Bearing Clearance
Production #1...............0.0008-0.0020 in
Production #2,#3,#4......0.0011-0.0020
Production #5................0.0017-0.0032
Service limit #1.............0.0010-0.0015
Service limit #2,#3,#4....0.0010-0.0025
Service limit #5..............0.0025-0.0035

I mesured the main bearings clearence between the bearings and crankshaft only.

 

I also measured between bearing and crankshaft and in the vertical orientation. The concern is using the plasitgage. The mark it left on the bearing vs the crankshaft was two diffferent thicknesses.

IN realation to the clearances you posted- I suppose the rear main is bearing #5?

 

Ok. Yes #1 is the front of the engine.