Ok, maybe I'm just an idiot, but here goes. My timing plate has marks on it as follows:

12 8 5 0

I would assume that the 0 on the far right would be 0 degrees, or TDC, and the marks to the left would be 5, 8, and 12 degrees BEFORE TDC. I just bought my truck about a month ago, and decided to hit it with a timing light, since it was running a little rough, and not passing emissions (failed idle hydrocarbons). When i examined the timing, it was off the scale, past 12 degrees BTDC. My tag on the underside of the hood specifies to time the engine at 0 before TDC. I plugged both vaccuum lines to the vaccuum advance, timed it, corrected idle, and it ran like crap (ran smooth, but not power at all). I set it back to where it was and everything was fine again. I would have been happy with that, but I did some off-roading, and while on a steep hill climb, the engine started pinging. I immediately went home and set it at approx 8 BTDC to compensate. I don't know if my distributor is off a tooth, or if my timing chain has jumped a tooth, but I don't think I'm getting an accurate reading, since the engine runs like crap at 0 BTDC, which is specified on the label under the hood. My head is currently being serviced (rebuild plus RV cam) and I'm replacing the stock carb with a Weber 32/36. I guess i'll know soon if it had jumped a tooth, because I will have to re-install the timing chain (got a new timing chain, tensioner, metal guides, gaskets). I guess i'm just looking for re-assurance that I should be timing to the 0 mark. Also, should I still be able to pass emissions with my new weber and mild cam? Thanks in advance for any help regarding my dillema.

 

Anyone?