I have had both A14 and A15 race engines over the years with same head. The A15 was 40thou over giving a capacity of around 1540cc it was a good grunty motor.I sold the bottom end to a freind
who had blown his stocker I kept the head as it is a work of art:) I purchased a rally car several years later with lots of bits and pieces to my suprise in a box was a set of A14 120thou
over pistons and a A14 crank with linished rods ect. The block I use at moment is actually a A15 there is no difference in A14 & A15 block anyway so I had it bored decked ect and fitted all
the good bits in. I used a different experimental cam this time with heaps better results. (cant remeber the exact spec) anyway once it was all together I was suprissed with the amount of
torque even with the more radical cam power peeked at 7000rpm and would rev to 7500rpm all day long.The A14 also has what is called a square bore withthe 120thou oversized pistons it had same
stroke as boresize.
All in all even though the A14 had a smaller capacity of 1510cc it was a heaps better engine maybe the cam helped could have also been the different jetting and chokes in webbers.
I actually have a freind who spent over $6000 on a A15 total capacity of 1608cc even though it had more work done it didnt quite have the same hp its strange how some engines are just freaks
of nature. Anyway I hope this info helps I hope I havnt dribbled on too much if you want to know anymore give me a yell.