Lee Cobb Posted April 7, 2021 Share Posted April 7, 2021 Evening all, We are in the middle of rebuilding a 1940 248 engine and come upon a interesting issue. According to Motors Auto Repair Manual the bolts for the main bearings are supposed to be torqued to 90-100 Ft. Lbs. The issue is that once we hit about 55 Ft Lbs we can no longer turn the shaft. Standard bearings and crank are .010 over and are smooth as silk up to that torque. Anyone have any input? Link to comment Share on other sites More sharing options...
billorn Posted April 7, 2021 Share Posted April 7, 2021 Are you using the shims? Link to comment Share on other sites More sharing options...
1939_Buick Posted April 7, 2021 Share Posted April 7, 2021 From 1942 Buick Shop manual Link to comment Share on other sites More sharing options...
Janousek Posted April 7, 2021 Share Posted April 7, 2021 Are you saying you put standard bearings in a .010 over ground crank? Link to comment Share on other sites More sharing options...
Lee Cobb Posted April 7, 2021 Author Share Posted April 7, 2021 Allow me to restate: The crank was ground to .010 and the bearings were replaced with .010 bearings. We do have the original shims, but at this moment none are being used. Does anyone have any documentation on those and placement? Link to comment Share on other sites More sharing options...
Robert Engle Posted April 7, 2021 Share Posted April 7, 2021 Use plastigage to check your bearing to crank clearance. Rough rule is .001" per journal diameter. Bob Engle 2 Link to comment Share on other sites More sharing options...
Morgan Wright Posted April 7, 2021 Share Posted April 7, 2021 16 minutes ago, Lee Cobb said: We do have the original shims, but at this moment none are being used. Mine had 4 shims on each bolt and plastigaged down to 3 on some bolts and all 4 on the others, never 2, so if you have taken all your shims out I'm guessing you need to put most of them back. Link to comment Share on other sites More sharing options...
pont35cpe Posted April 7, 2021 Share Posted April 7, 2021 Are you aware that all the main journals are different diameter size, don`t mix them up. I had to shim the main bearings on my `41 248 engine. 1 Link to comment Share on other sites More sharing options...
Lee Cobb Posted April 7, 2021 Author Share Posted April 7, 2021 yup, we kept them in order since removing them originally Link to comment Share on other sites More sharing options...
Lee Cobb Posted April 11, 2021 Author Share Posted April 11, 2021 Shims for the win! 2 Link to comment Share on other sites More sharing options...
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