Alright so i just bought a GMC 2500 and its got a 350 in it. Its got a edlebrock carb and intake manifold with hedman headers to flowmaster glasspacks. The guy said its it was bored out to 383 and the top end was rebuilt. So i got it and checked the timing and it was set to 13 degrees advanced at idle thinking that was to high so i set it to 8 degrees witch is around factory specs. Well i go to drive it the next day and its awful. i step on the gas and i get nothin then power then nothin just off and on and its backfiring like crazy. Im guesing he put in a hotter cam or something but i dont have any specs on it so i dont know what to set the timing back to. should i just set it back to 13 and be done with it or try and set the timing by ear or something? i feel like with that setup it should have been producing alot more power than it felt like it was. It sure sounds nice but she aint quick. could just be that its a heavy truck tho. i dunno

Thanks

 

If it ran fine at 13, just set it back there to start with - last guy put it there for a reason. Engine wants whatever it wants eg mine's happiest at 15 initial. Search around here to get heaps of advice on timing techniques - long and short is advance it where it runs best just before pinging happens. You'll have to try a few settings before you find it.

Edit: Also can't bore a 350 to make a 383, that's a stroker.