I was emailed and asked about the type 4 mains and asked about the issues in reassembling the lower ends
and thought I would share my responce to the list  

 The split mains type 4 bearings are too long and hold the cases open. On my engines I measure and align bore each block then install the center mains measure again and check for daylight. I typicly find the bearing is out of round and it also holds the case open. this means that as the engine runs the bearings mating surfaces rub and close down in time the 2 middle bolts loose there torque and the bearing clearance closes down to nothing. 
I like the mahle bearings becasue it has a harder steel backing for the split bearing. I also have the cranks cut to fit the bearing size on the mostly for the split main sizing because that is the only way to get the clearance right.

rebuilding is all about the clearances 

Bob Donalds 
Boston Engine 
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