Running rough all of a sudden

[jm29henry]

My 29 Briggs started running really rough ,at idle.it does run ok at a faster speed timing and points checked good I tried changing the carb off of my other good running carb and no change and it seem to me that it not getting enough full becouse if I back off the GAV it runs better but not great I did check fuel flow to carb and it is getting plenty of gas .there is no moisture on the plugs but look to have a light look of black but not heavy.. If the intake gasket was going could that causing a vacuum leek and making it run better rich.i do not see any signs of soot on the gasket and the manifold I am hopping head gasket ok and feel there would be any reason why that would go bad also motor has less than 2500 miles on it and compression is Good and even across the board any help would be greatly appreciated

[Tom Wesenberg]

Check for intake leaks, such as worn throttle shaft, bad intake gasket, or cracked intake manifold.

I open the valve on a propane torch and move it around the suspect area. If the leak is found the engine will smooth out.

[jm29henry]

Great idea thanks is it possible somethings could,be going on in the distributor or making the can run richer would make a difference with spark?

[mike657894]

if your coil is going it can run a little rough. my old coil would start to run rough as it heated up after 30 min of use. then stall out about 10 min later. feel your coil if its warming it may be going bad.

[Tom Wesenberg]

Don't overlook the distributor also, as I've seen a couple of them short between #3 and #4. Of course they short inside the bakelite body where the spark can't be seen. A quick swap will let you know if this is the problem.

[mike657894]

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one time... and this is probably not your problem. but... may be helpful. I was messing with the wire from the generator and left it loose but on the post. I went for a short testing drive and the battery cable was loose so it jumped off the post. when this combination of things came together. I was 1/2 mile from home and it ran as rough as a car can run with out stopping instantly. I was losing speed but the driveway was close and getting closer so I continued. puff puff BANG puff puff BANG puff puff BANG. So to my point. check all electrical connections and check your battery voltage. the model A unlike modern cars will run below voltage down to minuscule amounts of voltage.

[jm29henry]

What did I do now I replaced the the Whole rebuilt distributor, new cap ,rotor , reset timing and now she won't start I am pretty sure the armored cable is not to tight and grounding out I have to check for spark and see what I have old girl is probably looking for,attention and she got mine know

[jm29henry]

Tom and mike thanks so mush for the help,this is a learning process for me!

[Tom Wesenberg]

2 or 3 turns of the armored cable is all that it needs. If it's an original cable and hasn't had the wire replaced, you may have broken insulation and the wire will short to ground.

[99ZoomR]

Our old cars definitely keep us occupied! My A looked nice when I got her but I've spent the last 6 months "sorting" things out to make her a driver as well as a looker. (Steering adjustment, timing and crank gear, carb rebuild, leaky gas gauge, etc.). I found out after much trial and error and a test light that the pigtail wire on mine that's connected to the lower distributor plate had cracked insulation under the cloth covering which would short out when I'd move the advance lever. She'd start running rough and sometimes would fail to start. Replaced the lower plate and wire and now she runs and starts great. Good luck!!

[jm29henry]

Thanks tom I will back off cable and let you know