Spitfire Clutch Pedal occasionally goes heavy/ stiff, but then frees up

[SLeonard]

Looking for some sage guidance! Our Spitfire mkIV (with 1500 engine swap) has started to get an occasional issue with the clutch. This week, 15 miles into a drive, the clutch pedal went stiff and almost felt “rough” to press but still had full travel. On switching the engine off the clutch went back to normal and light. So, we drove home as didn’t want to chance it. On the way back it again went heavy in traffic for a moment then as suddenly went back to normal. 
 

Clutch fluid level is good and fluid looks clean. Not sure how old as it would've been the PO. 
 

Any ideas what might cause this before I started tearing bigger stuff apart?

Thanks everyone!!

[Pete Lewis]

two things come to mind....have you checked the crank has no excessive end float

and check the withdrawl fork pivot pin is in place and not dropped/dropping out

the end of the pin can be seen in the clutch Hsg. o/s of the casting yoy should see the hole   it must have a pin in it  these can fail and drop out the lever then 

can go solid/stiff    Clutch Housing and Operating Lever to FR33413 : Canley Classics  item 12 

Pete

Edited September 24, 2023 by Pete Lewis