Hello. My 86 K5 has a 305 from what I was told when I bought it and according to the diagram for the firing order on the Autozone website, the plug cables are exactly backwards to what they should be. For example my #1 plug is set on the back left side of the distributor but the diagram shows it should be set to the front right. The engine fires right up and runs but it sounds kinda rough. How can I determine if this firing order is correct? When we changed them around to the way Autozone showed, the engine wouldn't fire regardless of what we did. We swapped them back to the original positions and set it back in time and it runs that way. I'm just worried that if they are indeed in the wrong positions that it will hurt the motor. Any thoughts, suggestions, or guidance? I've bought new cables and plugs to put in it just in case they are the reason it's kind of running rough. When I bought it, the guy said that it was a 305 with 350 heads. It's had an Edelbrock performer intake and Demon Racing carb put on it. I don't know if any of this makes a difference or not. I guess the main thing I'm looking for is, will it blow up the engine to run it the way it's wired up or will it be ok as long as it's smooth? Any help is greatly appreciated. Thank you.

 

If the distributor was removed, then reinstalled 180* off, the plug wires would have to go back on oriented like you have described. Unless your distributor is controlled by an ECU, you shouldn't really have to worry about it. Just set the timing to 4* advanced in relation to the #1 cylinder after disconnecting/plugging the vacuum advance and you should be good.

 

Ah, I hadn't thought about it having been removed and reinstalled 180 out. Thanks for the info. That makes me feel a lot better about it. Thanks again.