Runs rough when hot

[Enrico8n47]

Hi, everyone, I've had a Ford 8n, has run well for years, I've accumulated about 150 hours on the present coil, points, plugs, condenser. I cleaned the points, set the ignition timing and tested, it was running great. After an hour of mowing, it lost power and was backfiring through the exhaust system. After it cooled down, I tested each cylinder, it was getting a strong spark, and it fired right up and ran without problem. The coil was bench tested and is within spec. I'm thinking either 1) the timing somehow changed, or 2) the coil may be breaking down from the heat of operation. I want to get some other opinions. Please feel free to opine or suggest additional tests. Thanks!

 

[5030]

Check the compression?

 

[EdGooding]

Are you still 6-volt?

 

[John0829]

Typical failing coil symptoms. While it is acting up, DO NOT wait for it to cool down, immediately pull a plug wire and check the spark I am sure you will see it is yellow and not blue like it should be.

 

[Enrico8n47]

Typical failing coil symptoms. While it is acting up, DO NOT wait for it to cool down, immediately pull a plug wire and check the spark I am sure you will see it is yellow and not blue like it should be.

John, thanks for your input, I figured that was the logical symptom.

 

[wolc123]

It might be a compression issue and you may need a valve job.

 

[Thomas]

Just shot...radiator fins clean?

 

[ultrarunner]

It sounds like a common old Ford problem with a bad condenser the cause.

Especially the backfire and lack of power.

If it was just lack of power or stopping it could very well be fuel related...

I have an old 1930's coil tester and so far only one bad coil have I found.

There were a number of imported condensers that failed miserably... especially after 45-60 minutes...

One guy ended up changing out several new ones.

I had a brand-new Ford Scrip condenser and said try this one... that was over 20 years ago and still running on the one I gave him.

 

[Enrico8n47]

UPDATE: The coil was replaced, all 4 plugs were checked for color and gap, all normal and not worn out. Still harder to start, backfires and runs rough when warm. I just pulled the distributor to check timing and dwell, they are as close as I can get to spec using Tim Ponn's Grand Valley Tractor 8n front distributor adjusting tool (great product!). Next I'm going to try new points & condenser, since I heard that condensers have been problematic in recent years. Points and condenser are relatively inexpensive and simple to change. I prefer to try less expensive remedies first, and really don't want to do a valve job on it. Air flow and fuel flow are good, so it should be a spark issue.

 

[DarkBlack]

Have you checked your valve clearance?