BE-FAQ - Words on Plastigage
Now here's a word about plastigage. It's not accurate. It's just a sanity check.
All of the BE Bearing wiki specifications were developed using bore gauges and micrometers as a race engine shop would do to measure clearance. So you can't really directly compare plastigage to bore gauges and micrometers.
Here's a real case where this came to light. BE had a customer measure 0.0010 inch with plastigage. He did the right thing and immediately stopped the installation. BE paid to have the bearings sent back to them next-day air. Bert measured them with plastigage too, then he measured them with bore gauges and micrometers. When Bert used plastigage, he measured about 0.0015 inch. However, when he measured with bore gauge and micrometer, it was 0.0026 inch clearance.
If you are in this same situation, BE can't really tell you what to do. That's between you and your shop. If you or your shop feels uncomfortable with your plastigage measurements, then we will send a replacement set of bearings that were premeasured inside a set of connecting rods and verified with acceptable clearances. If you do decide to replace the bearings with a new set, this might not be fast though. It could take up to two weeks before we have time to measure a full set of bearings in connecting rods and verify their clearances specs.