Shmastigage???

[GreaseMonkey79]

I just got .003 for main bearing clearance using Plastigage. A guy told me that my only two options were shimming the bearings or regrinding the crank. I don't like the idea of building a nice engine with shims in it, but maybe that's ok????? What are the increments on over sized bearings?

[534BC]

Welcome to automotive forum. If .003 is too much then another option is to resize the main housings on the low side. If you're dealing with a standard size then lots of bearings used to be available in .001, .002, and .003 under.

I would not recommend shimming the bearings at all, and if at all possible get the housings/bearings checked for size and the main journals checked as well.

Plastigage can be unreliable and read real high if it has dried out or is old.

[maxwedge]

Good pont on the shelf life issue, it can also melt onto the envelope in extremely hot weather, changing the readings. Also when checking the mains the block should be upside down on an engine stand with the weight of the crank on the upper half.

[GreaseMonkey79]

Max, the clearence was checked in the same conditions you described. I had just bought the plastigage from o'reily's and it seemed pretty fresh. I also used two different sizes, .001-.003 and .003-.006, and both gave a reading of around .003. It was enough to leave me uncomfortable, so I took the short block back to the shop and they are going to mic it out. Looks like the crank may be going .020 under.

[534BC]

I'd trust the plastigage in that case. Especially if you checked all the mains. Lots of shops will grind on the low side thinking that it is "safer" and then install a hv oil pump to compensate.

If the crank was already ground (regardless of the diameter) rather than get an unessecary grind perhaps a line hone can be gotten instead and then spec it out on the low side.