I have a 1927 Tudor with a NH carb and a roller timer with good coils. Runs so so in low. As soon as I go into high it starts popping and cracking through the carb and goes away when I go back to low. I have all tight connections as far as I can tell and carb is cleaned out as well as I can tell Any suggestions? Thanks Ray
Slow gas flow. Popping and crackling through the carburetor is the same as a welding torch popping with too much air. Check the fuel flow and air vent in gas tank cap.
Check the timer. I had that happen and found one coil buzzed all the time (faintly). It was shorting around one timer terminal in the timer case hole. I cleaned it and put some insulating washers in and it worked fine. I believe many timers are discarded because of this problem and only need better insulation.
Ray, more here, be sure to listen to everyone that posts because it could be several things. So, we are giving you a hunting license.
We have a 1924 Studebaker in our family and it was running poorly. I said it could be carburetion, the ignition, or the valves. Guess what, . . . . it was all three.
What happened to Richard happened to me as well. Had your exact symptoms. The insulator washer on one of the timer terminals was crushed. Was a rebuilt roller timer with straight sided terminal insulators instead of beveled.
Thanks guys! Well I think it defiantly is a combination of things. I cleaned and regaped the plugs. Had two faulty plug wires. Cleaned the timer and then made sure it was well insulated. Ran a lot smoother at an ideal. add a load it popped and cracked again. So now I think its time to open up the gas flow. The elbow into the carb only has an 1/8" opening. Hope that will cure it!
Ray, that's a bit small and remember our Studebaker had three problems you are resolving two. It will get better with each thing you do to improve things. But, I doubt that it is your valves. We had between 20 and 50 PSI compression and improved it to 85 on all six when we re-did all of the valve stems and ground the valve faces and seats.
Do you have an actual miss or is it just a noise and are you sure it isn't happening to a lesser degree at lower speeds? I can't see a shorted coil doing this at higher speeds only. A short's a short it would be there constantly. I think your problem is there constantly just less apparent in low. You could be gas starved but a poorly adjusted intake valve (barely seating) makes a bit more sense in my book.
You also say it runs so-so in low. Take a compression test and find out the engines condition.