That would be the LAST RESORT on a timing chain/guide replacement.

At this point, best bet is to remove all the rockers and retime as already stated.

You can try to back off the crank, usually 90 degree's off of top and retime the cams... be very careful...

Pulling the front cover on a m117 is a job and problematic at best.
Truly not being ugly, if you botched the chain you dont even want to think about pulling the t/c cover...