Hi Phil, thanks for the quick reply.

I suspect that's part of the problem... there aren't 5 marks on the crank pully; there's 9. I don't know if this is a standard crank pully since this is a 2 groove one for A/C. The markings aren't numbered aside from what looks like a poorly stamped 0 (really light on one side so looks more loke a C) next to the 3rd mark in. All the others are either in the middle of the flange with a round punch mark in the center or offset towards the outer groove and without a punch mark. Especially nice is that the markings aren't all that evenly spaced.

I tried both the '10' and '20' spots for timing and both still backfired. If I rotate the distributor to get the highest idle RPM, that puts me around where '35' would be.

As for the valve lash, well, no idea why that would have anything to do with it. I guess my thought was to put everything back the way I found it since the reason wasn't making itself apparent. Oh, and I was using 1500 RPM to set the timing because that's what the both the service manual and Autobook manual say to do. Seems kinda silly to me, but then again, I'm also the one having all the weird problems. :-\

-a.