Can you carry out a plastiscene test and find out what minimum valve piston clearance is?
It is a very usefull test
Not easily and anyway, pointless unless your going for custom ground cams plus we already know the max useable lift is around 10-11mm!
had a look at a few bits today, the pistona have a very slight dish but, they also do NOT come to the top of the bore like the 2.5 and 3.0!
So, we do at least know for definate how the compression has been lowered!
So unless there are some 2.5 style 2.6 pistons (there isn't) skimming is pratical - provided the inlet divider is trimmed as well.
Doing this on my Sunbeam worked out a 60 thou skim was possible, that was quite a bit higher than before.
Thinking of trying 20 thou if practical - if I get a spare set of heads to fettle before May - no hope of reburbishing and regrinding in two heads in one evening.
I am aiming for 10.8:1 as that will work fine, but I don't think I could skim that much off.