Delorean went BOOM

["bepositive2000" <BePositive2000@xxxx>]

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.