1950 Model M - Continuing Saga!

Danny in CO

Well-known Member
We are slowly making progress with the basket case Model M.

We still have an issue with it backfiring (popping) back through the carb and blowing oil out the breather. Valves are set correctly and it is timed correctly (I think). Timing light on #1 plug (closest to radiator) and I see DC in the timing window at idle. What would cause it to back fire?

New plug & wires. Distributor has an EI, so no point and condenser.

Sometimes it seems to run fine and then it starts backfiring again.

I have a video that I will try to upload of it running and backfiring.
 
Do you have an intake valve sticking? Is the valve spring area being lubed?

One of the "bolts" holding the valve cover on a 40 is special. Has a slot in the "base" to allow oil to be sprayed into the valve
spring area.
 

Thanks for the response.

When I checked the valves I didn't see oil to them. I was concerned about that. But that is down the list of getting it running. There are 2 bolts holding the valve cover on. Do you know which bolt it would be?

I'll take the valve cover off and start it and see if a valve might be sticking.
 
On the 40 I am working on, it is the rear bolt. If you look at the head, there is a fitting in the rear of the head to which an oil
line attaches. Then a passage is drilled to the rear bolt location.

The two bolts are the same length, but one has a slot cut in one end. I don't know how far you are supposed to turn it into the head.
 
CHECK THE FLY WEIGHTS IN THE DISTRIBUTER AND MAKE SURE THEY ARE NOT STICKING AND TIME IT WITH THE LIGHT AT HIGH RPM, NOT LOW.
 
<Roger in Iowa: On the 40 I am working on, it is the rear bolt. If you look at the head, there is a fitting in the rear of the head to which an oil line attaches. Then a passage is drilled to the rear bolt location.

The two bolts are the same length, but one has a slot cut in one end. I don't know how far you are supposed to turn it into the head.>

Thanks Roger, I'll check the bolts.


<Courtland508: CHECK THE FLY WEIGHTS IN THE DISTRIBUTOR AND MAKE SURE THEY ARE NOT STICKING AND TIME IT WITH THE LIGHT AT HIGH RPM, NOT LOW.>

Thanks, Courtland508, I checked the weights when we were working on the distributor. They are good. I'll reset the timing at high RPM and see if that helps.


<Dieselade: is your distributor rotated 180 degrees wrong way?>

Thanks, Dieselade, the distributor will only fit one way because of the offset on the bottom. We timed the oil pump according to the manual.
 
Timing cannot be too far off if it runs okay for awhile and then starts to backfire.

The only source of backfire has to be thru the intake valve. Valve has to be open some and cylinder charge has to be fired by ignition
or hot spot in cylinder.

Still think intake valve is sticking. Run it with the valve cover off. When starts to backfire lube the intake valve stems and see if
it stops backfiring.
 

Thanks Roger, That's my plan the next time we work on it. It's a neighbor's tractor. Right now the lift didn't work. He found a split hydraulic line going to the pump at the front of the motor. At least I assume it is the pump.
 

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