Hi Everyone, It's been a couple long weeks. You guys will probably get a BLAST out of this. I did?LITERALLY. I just finished replacing a couple of bad rocker arms on the #4 cylinder. The oiling holes were plugged and the cam eventually made a concave slot in the rocker arms. Cam looked fine. After reassembling the head, intake, etc. and the first trial running, the car failed to start. I did hear a loud hissing sound. Fuel pressure was good at 44 psi (I have a fuel pressure gauge installed full-time). After about a minute of cranking, I heard what sounded like a hissing sound. Next attempt at starting, the hissing sound repeated then a LOUD EXPLOSION! When the smoke cleared, there was no flame. However, the muffler was BLOWN APART and my ears are still ringing! Has anyone experienced this on a DMC or any other car for that matter? Any idea what I did wrong? Any guess on what the explosion did to the engine? I was extremely careful in following the proper steps on removing & replacing the head. I've had the intake off of the car at least 4 times and am fairly knowledgeable in the fuel system. I was very careful to follow the head torque & angle tightening recommendations to the T. (I was ready to run the engine for about 30 minutes then re-torque according to the manual when the explosion occurred.) Using a short piece of box tubing, I made a bracket to secure the cam chain sprocket before removing the cam. (I did not remove the timing chain cover.) I am positive this sprocket and chain did not move. Since it was the 4-5-6 side, I was not able to visually see that the #1 piston was at T.D.C. However, I did remove the #1 plug, visually look to see if the piston was at the top of the stroke, then I did 2 revolutions of the crank and waited for the surge of pressure from the #1 cylinder to verify that I was at T.D.C. It was at this point that I set the distributor rotor to the #1 location as installed the distributor. I marked the timing location of the distributor before removing it, but unfortunately I did not note the location of the rotor. There are two identical marks on the crankshaft pulley and I thought the procedure I followed would identify which one was correct, (It worked once before); however I am now wondering if I got the position off by 180 degrees (or 1/4 stroke). This seems to make sense. Valves would open at the wrong time letting fuel run thru the engine and into the exhaust without burning. Then, after cranking for a period of time sufficient vapor built up to the point that a plug ignited the fuel all the way to the exhaust where there was the most vapor accumulated. Am I even close to being on the right track? Also, does anyone know why there are two marks and if there is a way to determine which is which? Was the #1 piston not finishing the compression stroke when I felt the pressure in the cylinder and should I have waited another half revolution of the crank to set T.D.C.? I also verified that all plug wires are to the right cylinders. One last move that may have contributed to the explosion: I placed a few drops of gas in the intake (just a few drops but probably a dumb move). Anyone interested in an "exploded view" of a Delorean muffler? I have to admit it is difficult to maintain my normally positive outlook and sense of humor after being so careful to do a quality job and still having this happen. I even shot photos of the various steps in case someone else could benefit from my experience.