Going up a steep hill as the load was at max there started a loud popping, I assume it was backfiring through the carburetor. I slowed down and pulled over for a check under the hood. All seemed normal and running as usual. What is the most likely cause? Did I have the timing a bit to advanced? That is my assumption. Other ideas?
Was the noise in the engine or the driveline?
Did the power decrease? I found out one of my engines which had poor pulling power on hills or when shifting into high was caused by a head gasket blown between two cylinders. See picture attached. It ran fine on level at high speeds or when in low or Ruckstell, just low engine speed it would not pull very well. I also could not seem to find the "sweet spot" on either the fuel mixture or spark. You can find out whether this is the case by taking a compression test. If it is low on two adjacent cylinders it could be a gasket. Or another thing which would cause similar symptoms would be a stuck valve. Especially if it is an intake valve could cause popping in the carburetor.
Sounded like it came from under the hood. I had very recently changed my old anco tymer for a new one. Even set up per direction, the sweet spot seems mildly different from the previous unit.
So I can see how an intake valve sticking open would cause this symptom. Perhaps a bit of something got hung up under it then cleared? Any other possibilities? I can't come up with any other things that would make such a loud popping, then go away with no further evidence of malfunction.
Another possibility would be a ground on one of the timer wires which would make the spark come during the intake cycle. Sorry that the symptom you describe could be caused by several things. Maybe it was a chunk of carbon under the valve and it was a one time occurance.
I have found that being too lean mixture on a big hill pull is not good, especially with too much spark advance. Consider that cars with automatic spark advance retard the spark some when manifold vacuum falls (wide open throttle at lower engine speeds). On a big climb in high gear I always move the spark to the middle position (car running on mag) and open the mixture about 1/4 turn (NH carb)
I believe the Les has found the problem. Carburetors work much like welding torches. They make black smoke out the tail pipe when rich and pop just like a welding torch when there is too much air. So richen up the jet while climbing and retard the spark at the same time. More when running on battery and to the correct place on magneto.
That sounds reasonable. I remember just before that leaning the carb a little bit. Never had that happen before. Will do some further test drives today to get my relined rear brakes seated and see if the popping reappears at any time.
It also seems possible the tymer may be at fault. Will check for unwanted contact inside and out.
You changed the timer and the problem arrived. Royce often offers that the timing on ANCO timers can be erratic. Perhaps you should put the old one back on and see what happens.
It only did it for that few seconds, now I have driven it several days with no recurrence. The new timer is working great, no unwanted contact areas inside or out. Not sure what it was. I vote a bit of something hung up an intake valve momentarily, then blew through. Or it could be the carb inlet valve got a booger in it and wasn't shutting off. Perhaps the mixture was overly rich
Perhaps you were low on gas and the carb was starved for fuel going up the hill. Look for horses before zebras.
Tank was full, plus it has tank in cowl (1926).
Was it warmed up when that happened? Some cars will do just what you said when cold.
Norm, no it was fully warm.
I agree with Norm, sticking valve. It may never do it again, then again it may.
Tom, that is all I can come up with too.