We are in process to build a street built 403 for our 64 Cutlass and notice that the No.3 main cap installed backwards....like :

4 M
M 3
2 M
1 M

Bore looks wear but bearings looks okay, so i donīt think its came from factory...but how knows?
(can to try insert pics if help)


We donīt want the block line hone only decking, milling heads so what we have to do....put the caps in the correct position or ...

 

Measure the bore with the cap torqued in place and see if it is round. Then if you can get plastigage use it to see if the material squashes evenly on the crankshaft journal of that cap when torqued and that there is proper clearance. If plastigage does not squash evenly across the bearing something is wrong.

How do the tabs on the back of the #3 bearing line up compared to #'s 1, 2, and 4? They should be identical.

Does the crankshaft turn freely when everything is in place and torqued?

Any idea how long it was like this?

Does it look like a bearing was rotating inside the bore at any time?

Are the tabs on the back of the old bearing still good?

Pictures of the bore, inside of the cap, crankshaft journal, old bearing from the crankshaft surface and the bore side of the old bearing would help.

Good luck and keep us posted!!!