Small Block & Big Block Chevy Specific - 350 crank main cap help

alright.. while installing my new crank into my 350. i have a slight problem. the crank freely spins with the rear main cap in place, and also with the center cap in place.. and with the front cap in place... but when i put on either of the remaining 2 caps, the crank will not spin at all. do i have an end float problem? (i measured it to be fine). all my bearings seem to be good as well as my main caps clean. should i tear back down and check under the block bearings for debris? any info would be apprieciated. im 18 attempting to build my first small block with the help of some family and friends

Not trying to insult you but are you putting the caps on in the same place they came off? You should be and make sure they are turned right(arrow pointing forward). Also look at the bearings and make sure the size .010, .020, std. or whatever your crank is are stamped on the back side and correct. If that doesn't work then get some plastigage and check the clearance. If that fails then you will probably have to get the block line bored/honed. Hope this helps. Good luck!

If you got this as a used block it may have an odd cap--one that didn't originally come with it. In that case it needs to be line bored.

If the caps came from another block or have been mixed up you need to have it ALIGN bored and honed. After the machine work be sure to at the very least use some plastigage if you dont have a dail bore indicator. If the block has spun bearings its very possible the main saddles are swollen creating a tight bore situitation....

What type of crankshaft is it, I have seen stranger things right out of the box.