Thread: 350 crank main cap problem

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alright ill go back and check that. what clearances am i looking for?

You should have a Chev manual that is specific for your engine that has the torque specs and the clearances for that motor. For a given clearance, for instance the main bearings, there is a high limit and a low limt in the spec and your measurement should be in that range.

There are tolerances for the piston to bore clearance, the piston ring end gaps, the rod bearing clearance, the main bearing clearance, the rod side clearance, the crankshaft end play, etc. Every clearance needs to be checked to verify that it is within the tolerance range.....parts wear and engine machine shops make mistakes.

Again, get the torque specs and clearances.

Mike in Tucson

By the way, if you are not familiar with Plastigage, it is a neat product that has been around for a zillion years. Plastigage is a squishable plastic material that is made to a very precise diameter. When you put it between two parts and squeeze them together, the plastigage flattens out to the thickness of the gap between the two parts. Thus, since the diameter was known, the cross sectional area is known. From that, the width of the squished part is a function of the thickness of the squished part....the area stays the same as before the squish....from a pictorial width chart on the package, you match the width of the squished section of plastigage to the chart and it tells you the thickness of your clearance gap. It's easy and requires no expensive tools.

It works for rod bearing clearances and main bearing clearances. The plasticgage comes in several thickness ranges and is color coded so you know which one you are using.

mike in tucson

You could have a bent crank, or the block could need align boring. If the Plastigage doesn't find the problem, you'll need a dial indicator and stand to check for wobble in the two main journals. Hope its the bearings!