Lately it seems like my 1923 touring/pickup conversion pops once out the tail pipe a second or two after I shut it off. It didn't used to do that, should I worry about it?
I usually let the car idle for a couple of seconds with the spark advance lever fully up after I pull the car into the garage, should I be doing something else?
Sounds like you might be running a little rich.
Make sure all cylinders are firing. (Spark plugs, coils) otherwise try to lean it out just a little. Also maybe let it idle a little longer before shutting off (10-15 seconds)
Turn the ignition off before you retard the spark and then retard it after you shut off the engine. What you have is a hot manifold caused by fuel still burning as it goes out the exhaust valve because of the late spark. This heats the manifold sometimes red hot.When you turn off the ignition switch as the engine is still moving it sucks in some fuel which does not burn because the switch is off, and so the fuel goes out the exhaust valve where it is ignited by the hot manifold resulting in the pop.
Ok, thanks everyone. I'll try letting it idle with the spark advanced before I shut it off, then retard the spark well after it shuts off.
I'll also try running it a little leaner.
Don't run too lean. If it is too lean the exhaust valves will run hotter and the exhaust manifold will glow red in low light.
Because of the delay in popping I wonder if there is a leaking exhaust valve that is leaking off a charge of air/gas after the engine is shut off. Maybe a compression check would be in order.
Yeah, sounds like the fuel mixture.
My car does that too when I run it too rich. I scared a bunch of Amish kids once when it went off like a bomb. They ran under their buggy.
There's no need to idle with spark retarded before you shut it down, but then it doesn't hurt anything either...
I run with the spark retarded 4or 5 seconds before switch off because of the free starts and both of our T's are stem wind.Neither T has ever popped back but the Model A will sometimes.The Canadian assembly team taught me about the free starts and the spark.I think if you run a Anderson timer you need to retard your spark while the engine is still moving? What work's for me might not work for others but i remember maybe 19 years ago when our first T taught me not to forget!!!! I was lucky and never broke anything but it tried to kill me!!!!!!!!!! Bud.
My '25 will do it if I don't retard the spark a bit and let her a few seconds that way before shutting off the ignition.