3mm OIL RING with compression ring size .0591" (1.5mm)and one piece oil ring .1181" (3mm)on p21253 pistons giving 9.7cr on 1275cc. std ring size
For performance see steel ring set with 3 piece oil ring as favoured by engine builders
C1818.000 Rover piston were stamped 21963 for high compression but 21962 seems to be stamped on some from Metros or overseas cars from customers claims.
Rover piston high compression 21963 and AE replacement was 21253 and the latest number for AE Nural is 87-524100---Does this get confusing?
So lets clear it up; the easy way to identify the piston and corrrect rings are as follows-they are made from the same piston slug with same dish but the high compression version is easily identified by the lower oil ring being 3mm wide and the top ring gap to the crown is 10mm deep.
The low compression version has 4mm oil ring and a shorter length top ring gap of about 7mm to the crown/top. The gudgeon pin is moved on production to give the higher compression ratio and lowering the rings giving a larger top ring land for strength. Rings for 3mm lower oil ring type are R41570.
if you have 4mm oil ring use
R35960-00