Tried to get the CCOV out today. Used the wooden plug methode a couple of times but the sucker woudn't come out... Decided to leave it in for this season and make another effort this winter. Till that time, I have to leave it on high compression.
2 problems
1) More Running time will not make it any easier
2) Running at high compression can be very hard on the engine, it was only designed for starting and then to be reduced.
Lister recommended leaving JP engines (same COV system and compression ratio's as CS) on high compression for sustained running at low revs below 850 rpm (max 1200 rpm).
JP2's and 3's are a popular fitment in narrowboats used on the UK canal network. I know of some that have run 10,000 hours plus under this light duty cycle always on high compression. My own experience with a JP2M marine version in a narrowboat and running on low compression, is that head temperature is simply not high enough below 750 rpm to allow proper combustion, so engine smokes noticeably. Since shallow canals limit speeds, its rare to be able to use more than say 600 rpm, higher and the boat actually slows as stern and prop dig into mud, hence engine remains in high compression. When on a river with lesser speed restrictions and the draught to allow prop to bite and do some serious work, I do often use low compression but its more to do with exercising COV's.
Bear in mind also that later CS and the 1500 rpm JK series which superceeded the JP's, dropped the COV's completely, although they did reduce the fixed CR slightly to 17.5:1