I was looking at a '78 Blazer yesterday that someone had for sale cheap, but when running it would backfire through the carb. He said that when he installed the dist he must have put it 180 degrees out, therefore causing the backfire. Is this true, if not what else would cause it to do this? What can this damage? It just makes me leery as to why he wouldn't fix it if he is trying to sell the Blazer. Other than that the engine seemed to run fine. Any input would be appreciated, thanks.