Here is what I know so far...my 1937 1/2 ton with a 235 was running like a top until a week ago. It now starts and idols just fine but when I go to accelerate it seems to lose power and backfires through the exhaust....sounds like a popcorn popper. It always seemed to be a little cold blooded but once it was warmed up it use to run great. I have checked the plugs...dry and a bit on the black side. Vacuum advance seems to be working correctly. I have good fuel flow from the accelerator pump. I have checked the exhaust and there doesn't seem to be any blockage. Nothing has seemed to change with the timing as well.
