Is it possible to install the timing cover on a '70s SBC without loosening the oil pan? (it's in a boat). It came out tough, but seems impossible to reinstall...

 

Gotta clip the "wings" off the corners of the INSIDE lip of the cover. They're squared-off from the factory. Gotta cut them at an angle, taking off a fair bit of metal, then the cover will slide back in place.

Also, rotate the crank so the keyway in the crank is pointing to the side and not catching on the timing cover seal as you slide/wiggle the cover back into place.

In cases like this, RTV is your friend. Did one just recently where the half-moon pan seal was toast. Loaded in a big blob of RTV in the "groove" on the timing cover in it's place and hoped for the best- sealed up just fine. Also, you want to use a little blob of RTV in the corners where the "half moon" in the pan lip meets up against the flat part of the block and the corner of the timing cover before you put the timing cover back in place.

 

Have done this by loosening the front 3 or 4 bolts in the pan, drive a screwdriver in from the front to lower the pan just a little, put the cover in and sort of 'inject' some RTV in the corners. Pull screwdrivers out and tighten. Won't leak if you're lucky.