Traction engine troubleshooting

Today I started troubleshooting a potential engine issue in my Traction Avant.   When the engine is hot, it will sometimes smoke out of the valve cover and there is a single pulse of black exhaust like it is being caused by one cylinder.

My first test was to check the compression of the engine, quite easy on a traction engine as the spark plugs are easily accessible and there is a starter button in the engine compartment.  A compression check is always a good check to run on an engine to understand its health.

I found that #1, #3 and #4 had compression of 90PSI but #2 only had about 65PSI compression.    On a well running engine they should be similar.   The Traction engine is a low compression engine.   Running a compression check on a more modern engine would yield higher figures.

Next step was to do a wet test.  This is done by squirting some oil into each cylinder, and if the compression comes back up you know the problem is likely with the rings as the extra oil helps worn or damaged rings seal against the cylinder wall better.

In my case the reading hardly changed, so as I expected the problem is with a valve not closing properly.   My theory is that one of the exhaust valves is not sealing.      Next step will be to check the valve clearances.

Update 3/17:  One of the valves was found to be out of adjustment.