Years ago I had an Opel 1900.  It developed a horrific knock and vibration.
Just as I was about to remove the engine for a teardown it was suggested to
me that I try pouring a quart of transmission fluid down the carburetor.  I
started the engine removed the breather and began the process. By pouring
slowly and moving the throttle to keep the engine running I was able to pour
the whole quart through.  After one quart and one very large white billowing
cloud of smoke the knock was gone and the engine purred like a kitten.  I
replaced the plugs with some pink Beru ones. The Opel and I lived happily
ever after until a drunk in a pickup truck smashed it one night when I left
it parked on the street.

Rico Dagastino
Munford, TN