Luckily when we scrapped no.1 i kept a piston for reference, it seems to have been fitted with +060 hunter pistons (1787cc) and according to my Hepolite books these are less dished (higher compression) and have one less ring (lower friction) and were available in +090 a whopping 1821cc 
Hepolite 18861/k.
I shall further investigate whether there is a better alternative to these
"You,re only supposed to blow the bloody SLIDING doors off"
Hepolite 18861/k.
I shall further investigate whether there is a better alternative to these
"You,re only supposed to blow the bloody SLIDING doors off"