boggsy, I have just restored a"T "engine and I found the crank locked up on tightening the big ends and also the mains I double checked the crank journals and big ends for size they were perfect , checked they had the correct markings on the under size slippers, these were also correct. so I tried each big end and found they locked up, the mains were the same. What had transpired with a previous owner/mechanic had files the caps to tighten the clearance for the existing wear, so when the journals were brought back to a standard the con-rod and main bearing journals were now undersized, Had the mains reline bored to original size, the big ends were also resized , checked clearances of each journal, all ok, engine now turn over very sweetly Hope this is not your problem . I have been told it was a common practice with older engines. Saltiga