If you decide to pull the timing plate, here's a tip you might find helpful. You'll probably find the three slotted flat head screws used to secure the middle of the timing plate to the block can be a bear to loosen. I've struggled with (and mangled) too many of these until I finally took the time to figure out there had to be an easier way to do it. Try using a hand impact driver (the type that you whack with a hammer) with a screwdriver attachment large enough to fit the slots on the screws. Works like a charm. Not only can you loosen them easily this way, you save the screws and don't have to chase down replacements. Reverse the hand impact driver to tighten.
I made a screwdriver attachment by grinding down the shaft of a 3/8" hex bolt to make it fit exactly into the screw slot. I use a 9/16" socket on my impact driver, stick the ground-down bolt into the socket, and voila.
This should be a Tech Tip- I buggered up my front plate screws and never thought to remove them that way...
