26 is has a miss , runs rough at idle or high rpm.
Switched coils, cleaned timer, checked for leaks at intake
Cleaned coil box contacts
Tried different adjustments on carb with knob, tried changing spark advance.
Possibly carb issue? If so what?
Doesn't cough through carb but does out exhaust . Plugs are black and I can smell its very rich .
Help

It helps to have known good spares to switch to and see if the problem goes away.

With the engine running, ground out the spark plugs one at a time. If grounding a plug slows the engine, that cylinder is firing. If it doesn't, it isn't. Why isn't it firing? Bad plug, loose wire, stuck valve, broken valve lifter... That last one was my recent experience.

It's firing on all plugs. Coils are all new I borrowed them.
Las Sunday it started missing while driving and I thought coil.
If ran so bad I didn't think it would make it home. How do I check valves ? Could I be a carb issue? Very hard to start today. Never had that before.

Is it running a Vaporizer?

NH carb.

It's a 1922 motor. No noises in engine . Unknown condition but it looks like head has been off because it has paint and the rest of engine does not. I e owe ex it since May. Had it running good till a week ago

Is it firing on all cylinders, or is it just sparking on all plugs? Spark doesn't mean a cylinder us firing. If a valve is stuck open or isn't opening enough, it no worky. "It ran so bad I didn't think it would make it home." sure sounds like running on three cylinders.


With the valve cover off you can easily see if there's any problem in there. In this case, #2 exhaust has a quarter inch gap between the lifter and the valve. The gap is supposed to be a few thousandths. The bottom of the lifter is broken off. That's not the only possible valve problem. Sometimes they get stuck and don't close as they should. You should be able to see that too.

I'm not claiming this is definitely your problem, but it's certainly possible.

Thanks Steve
I will check the valves. I have to leave for Ohio later to pick up my wood wheels. Meeting Steve Hammott . He picked them up in Nevada last week on his way to Hershey . Waiting on his call so if I quit responding that's why.
Thanks for the help

Missing = not a carburetor problem. Shorting out the plugs is one way to isolate a weak cylinder. I usually just open the coil box when the car is idling and press down on the coil points one at a time. That way you can be sure all the coil points are in fact vibrating too.

If all the coil points are vibrating but one cylinder is weak, you can try swapping a couple spark plugs. Just because a spark plug will fire it does not mean it will light a fire in the cylinder.

Do a compression check.

Steve, I had the same problem with #4 exhaust. You cannot buy just one of those small bolts anyplace!

I stopped using adjustable lifters after that event.

Hi James,

Those bolts can be purchased here:

https://www.modeltford.com/item/3058MB.aspx

Langs may not carry everything, but they do carry a lot.

Is anyone else bothered by the angle of the spring retainer on that left-most valve? Perhaps the springs are too strong? T valve springs don't have a high compression spec.

Sometimes "missing" isn't quite the correct term, but it sure feels like it! I had a NH with a bad float valve that would stick....sometimes open, sometimes closed, and then sometimes where it would starve the engine of fuel and the thing felt like it was "missing", but it was actually fuel starved. Then you couldn't get it started, or would "miss" above 28 mph... Check that float valve and be sure you don't have the newer type "ball" valve.

KISS
Keep it simple stupid!
I forget that sometimes. My problems started with two bad coils. Fowled two plugs that were new about a month ago.
I started with basics again and checked each plug with it running ( screwdriver method) and found no change in motor on 1st two cylinders . I pulled out a couple champion X plugs that looked about as old as the truck and cleaned them , installed and problem solved.
It's parade bound tomorrow night.
Thanks for all info on the problem. I sometimes forget to start with basics. I just put the plugs in about a month ago so when I got good coils I was thinking carb or valves .
Running good now.
Thanks to all