Well, I got my '56 on the road this week, passed inspection Monday. This truck has run very little in the past 23 years. 93 k original miles, engine not changed except carb rebuild. Cletis helped me with a little initial antifreeze overflow, and generally the truck has been running well, except for unexpectedly dying at low idle and being hard to restart, as well as popping on acceleration (when lugging a little). Today I drove city traffic about 8 miles with a high idle(throttle pulled a bit), worked for four hours with the truck shut down, no gas smell, tightened some bumper bolts, then went to start up. As soon as the engine caught, there was such a big backfire? boom that my ears hurt- I could feel the concussion and felt the engine go rough, so I immediately shut it down, went to look at the carb, seemed fine (except I did not look down at the butterfly throttle valve), and then I noted the exhaust pipe seemed low. To my amazement, the muffler was blown open like a sardine can, and the heavy strapping holding it up had been blown apart too. This muffler is 2 feet long and 7 1/2" in diameter! A voice floated in from the street- " everyone all right in there?" "Yes- just a backfire" says I. The truck ran, loudly, and seemed to tend to stall when giving gas. I tied up the remnants of the muffler with the strapping, drove about a block, had very little power and a lot of noise, and decided a tow was my best option. I had been thinking about checking the timing, and had tried to increase the idle by opening the idle adjust screw a turn on Tuesday, with no change, so I left it. It seems to me there must have been gas/air in the muffler to do that explosion, and I am really looking forward to the collective wisdom of the folks in this forum to keep my next muffler from a similar fate, and to get a sense of what damage may have been done. The tow guy suggested a muffler with a larger outlet. The muffler is under the front of the bed, and a short tailpipe ends high before the rear axle. The engine side pipe is 2 1/2 " in diameter, and the outlet pipe is 2". The bends on the engine side probably bring it closer to 2" or 2 1/4" there.
