crank thrust, I need some

[BigBlueIron]

Doing a quick mock up yesterday D3 block fresh from machine shop, stock 390 crank turned .010 and .010. Fm125 bearings. The thrust bearings fit very tight in the block and the cap throw everything together for a measurement and I've got about .002 to .0025. Pulled crank and thrust bearings inspected deburred, resembled no change.  Reset top cap few times smacking crank back and forth no change.

Crank spins beautifully but not enough thrust clearance. What is the best way to gain some, remove thrust bearings and sand a little on the front side? Do these FM125 bearings normally fit that tight in blocks?

[blykins]

Check thrust with just the block side bearing first and see what it is.   If it needs adjusted, remove the bearing and sand the front surface on a very flat surface until you get the clearance you want.  I normally like to see around .005".  After you do the block side bearing, put the cap side bearing in and check it again.  If your thrust clearance is tight again, adjust the cap side bearing. 

[BigBlueIron]

Thats what I'll do.

Since I have your ear, I ran into another area of concern. Used low mile 2291 pistons, the pins fit free and smooth on one half of the piston but become very tight when fully installed. Like they must be forced in. Kind of at a loss as to why

[frnkeore]

To make sure that the block and the main bearings are in spec, the width of the block, should be .913 - .915 and the inside width of the thrust bearing should be .916 - .919 and the outside width of the thrust should be 1.116 - 1.118. The flange thickness should be .098/.099.

The dimensions given, are from Fords drawings. One of those dimension should be out of tolerance.