1949 clutch problem

[Jay Friedman]

I have a 49 with a manual transmission.  Its clutch is a Long 11CF which has centrifical weights on the pressure plate to exert more pressure as RPMs increase.  (The same clutch in various sizes was also used on Ford products of the era.)  

About 3 years or 15,000 miles ago I had the clutch rebuilt by a reputable shop who put new springs etc. in the pressure plate and relined the disc.  I did not change the throwout bearing at that time, but I did install a new gasket between the front of the transmission and the bell housing.  For the first couple of years the clutch operated perfectly, but then began chattering when releasing the pedal to engage it.  

My previous experience with clutches is that they usually chatter when motor mounts are bad or when oil gets on the disc lining. If the latter, in my experience the oil cannot be removed and the condition can only be corrected by stopping the source of the oil leak and relining the disc.  

However, after starting the car the first time of the day, this clutch operates smoothly and normally.  It only begins chattering after the engine warms up and the car has been driven several miles.  If I park the car overnight it goes through the same cycle: normal operation for the first few miles and chattering thereafter.  

The motor mounts appear to be good and I retorqued their bolts.  The motor does not appear to leak engine or transmission oil (or very little anyway) and only uses a quart of oil every 2,000 miles when on a long trip. The transmision needs occasional topping up.  

Can anyone help?  Thanks,

Jay