First off, I don't think it necessary to have the same discussion on two threads.
I pointed out to you that the gycol gasket leak reported at 49.5 hours of the 50 hr test was unrelated to 12lb/3000rpm operation as the memo states.
Again this does not state a requirement for automatic inspection or grounding of aircraft until the engine is inspected.
Dowding's memo states otherwise, and he states "...that some pilots were pulling the plug with little excuse on every occasion..."
http://www.spitfireperformance.com/dowding.pdf
An engine was flight tested for 49.5 hours of which 8.5 hours were at 12lb boost/3000rpm and the engine life was found to be little effected. I think that you might be having trouble translating some of the documents,
http://www.wwiiaircraftperformance.o...bs-14nov39.jpg
as there is nothing in the above to indicate excessive wear resulting from 12lb/3000rpm operation. The mods required for 12lb operation:
http://www.wwiiaircraftperformance.org/ap1590b.jpg
does mention the need for modified cylinder top joints, but then by definition these changes were all made prior to having the boost cutout modded for 12lb operation and the 14 nov 39 memo states that cylinder head problems were unrelated to 12lb operation, but I guess it was felt that more reliable cylinder head gaskets were a desirable feature in combat aircraft and the
Merlin in Perspective discusses the problem with coolant leakage in early Merlins and the design changes implemented to correct it. Rapidly changing cylinder head temps were likely to cause leakage problems but by definition prolonged running at 12lb will result in a stable cylinder head temp.