Plastigauge isn’t perfect but given the OP’s measurements I would have used it to double check myself in that situation. At least one rod or main would have been plenty to verify.

My question is has the measuring tool been calibrated/reading correct? I would double check with another tool, yes plastigauge would be a good double check.

Main bearing oil clearance measuring out of spec
 

I measured everything again, using the crank pin journals as baseline instead of the gauge pins and no meaningful difference.

I guess the plan for now is to use the 0.026mm tighter bearings by King Bearings. This conveniently puts my measurements back within the looser end of specifications or just slightly outside of them.

With the block assembled and torqued, without a crankshaft. I’m not sure how you would measure a loose bearing as you described.

I don’t get my equipment calibrated but, I have an assortment of gages and multiple calipers that overlap gages, and everything measures within 0.002mm. Plastigage measurements have been within 0.005mm of micrometer measurements.



You are correct. The original bearings measured oversized the same amount as the brand new King bearings and show almost no wear. A few little marks that look like they had some embedded debris at one time, but nothing of concern.
https://uploads.tapatalk-cdn.com/202...1de1f8ed08.jpg



Cheaper than machining anything! This is the route I am going, but will be all 0.026 tighter.

Yeah, it does almost seem like the block loosened up, unfortunately I don’t have bearing bore dimensions to verify!

Good to know. It looks like I’ll be running all oversized so no worries.

There is always the chance that the clearances were all out of spec from new. Maybe subaru is a bit sloppy building them. Maybe that's why they're a bit more prone to failure than other engines.
Oil pressure at idle spec is about 7psi according to toyota, crazy low. With main clearances set at middle of spec, 0W-30 oil and a WRX pump I get 12-15psi at idle.

Who wants to buy a couple of new short blocks, strip, measure and post the data. I'm sure we'd all be very appreciative! :)

That is enough double/triple checking to say your measurements are good.

Whether the micrometer he's using is calibrated or not, it almost irrelevant. He's setting the mic to the crank pin diameter, and zeroing the bore gauge to it. Are suggesting the bore gauge may not be tracking correctly over a <.002" stroke?

I was wondering if that main clearance was a cause of failures as well. Extra main clearance, means lower oil pressure for both the rod and main bearings. Then when someone gets rod knock it gets blamed on abuse or neglect.

I wish there was more data on what the main bearing shell bores should be. It seems like a pretty vital piece of info to leave out of the service manual.

Luckily this engine still had 20psi idle oil pressure with 0W-40, and down to maybe 16psi at worst idling immediately getting off the track and 240F oil temps.

Is the table at the end of page EM-115 about taking an *indirect* measurement of this? (I’m asking to check my learning from this thread, so please don’t feel compelled to reply if it’s any trouble.)