QuestionMr Benjamin - I have a '49 Super 8 that refuses to run in 2nd or 3rd gears at speeds over 35 to 40 MPH. Once it accelerates to this point, it hesitates, misses and stalls. It seems to be a fuel or ignition problem to me. I have flushed the fuel system, sealed the gas tank, and overhauled the carb. I have checked the valve timing, and the ignition timing is right on. If fact, with the vehicle stationary, it will get to very high revs without any problem. But put a load on it, and the above problem results. The only mod is a Pertronics electronic ignition, instead of points.
AnswerI am assuming here that the car has standard transmission - so when you say it "stalls" you mean the engine loses power, right? - it cannot stop turning unless it is out of gear somehow. Does it restart as the car slows down, or does the engine stay dead? What happens when you try to restart it?
There are a couple of possibilities - this could be vapor lock, especially if this problem seems to happen only in very hot conditions. It could also be a problem with the ignition system. There was nothing wrong with the original ignition system - I question the practice of going to something more complicated, especially when it is no longer something that can easily be diagnosed and fixed. If it were my car, the first thing I'd do is put the right ignition system back on it - I hope you saved all the parts so you can put it back right. I'd say that is the first thing to do.
If you feel the problem is heat related, you can put a fuel pressure gauge on the line from the fuel pump to the carburetor to see if the pressure drops when this symptom occurs - if so, you are having vapor lock. If not, the problem is probably ignition.
If the problem only occurs in hot weather, it could be vapor lock, though.
I'll quit typing now and wait for a response from you with some more information about the car (what transmission, and if it has overdrive, was it free wheeling when it stalled?), and what the ambient conditions are when it happens.
Dick
