Where to start... Well, I bought a truck that I had to do an engine swap on (1998 Silverado 1500, 5.7 Vortec). I did the swap and everything ran great. After it was up and running perfectly, I noticed a crack in the intake. I went ahead and changed the intake, and then the truck wouldn't start. I tried using quick start at one point, which produced a very loud backfire. After that, I had realized it was only the timing, so I set the distributor exactly as it should be, and then it started. After it started that time, it was knocking very loudly, and running rough. After starting it a few more times, the knocking is barely noticeable, but it keeps stalling, especially during acceleration (stepping on the gas in park). Is it possible that the backfire from the quick start could have caused damage somewhere? If so, could it have blown the engine completely? If not, what else could be causing the symptoms I've described? Could bent valves cause any of this? Please help! It sucks doing an engine swap, having it run great, changing the intake, and now having it run rough! Thanks in advance.