Hi Guys,
I havent posted for a few months, but am back and really need some advice.
Here is the backstory. I am working on a 46 ton and a half that belongs to a neighbor a couple of miles down the road. He bought the truck a couple of years ago, took it to a local mechanic for a laundry list of things to fix. The mechanic put it off for way too long, so the owner asked me if I would like to work on it. I said sure, in my spare time. I am a carpenter by trade, mechanic as a hobby. Mostly my wrenching is on old Dodge Power Wagons and the family cars. So, now the truck has been at my shop for almost a year, differnce being I have been working on it! I have replaced spring bushings and shackles, wheel bearings and seals, new fuel pump, rebuilt the carb, new intake and exhaust manifold gaskets, completely rewired it, converted it to 12 volt, added turn signals, and on and on. So now my list is finished, I thought I was done, but as a last minute thing decided to adjust the carb. The truck starts up fine, idles like a champ, drives around my shop yard fine. The problem comes when I start to give her the gas. About halfway through the pedal, it starts to spit and pop and backfire. It wont clear out at any point.
So, I had a friend who was helping me get it finished up, and he is a tried and true Chevy guy. He and I tried every possibility of carb adjustment, timing, checking the points, verifying the plug wires were correct, did a compression test and got 118 across the board, so seems to rule out valves. Tried running it off a gas can with fresh gas, no different, replaced the plugs which were black and sooty. We tried swapping carbs off my friends old Chevy that has the same carb, Again no change.
Its not a vacuum leak, We have checked and rechecked everything (except what ever the problem really is) and are stymied. The owner says he has driven it on the road and it ran fine. Supposedly the engine has been gone through, so I doubt it has slipped a tooth on the timing chain. The engine is not the original, it is a mid 50s 235. I feel like we have covered all of the ground we can for exterior things, now we are wondering if it could be off a tooth on the timing chain.
I am sure ready to be done with it and get my shop space back!
Thanks in advance
Tim