As my PB block has now been rebored to 62mm I was interested in working out the engine's (significantly) larger capacity.
Following the logic that 60 mm pistons in a PB engine give a 939cc capacity, or 15.65 cc per millimetre of bore size, that would suggest that a 62mm bore equates to 970.3 cc.
What intrigued me is that the same calculation applied to a PA engine (847 divided by 57) gives 14.86 cc per mm of bore size. Is there some other factor at play here - perhaps combustion chamber size - or is my maths incorrect?
My maths tells me that your engine capacity is 1002cc, you can't work it out by just increasing the bore size. The formula for finding the capacity of a cylinder is;- pi R squared x H.
Thanks for that - maths was never my best subject at school! I stand suitable chastened - but reassured about the monstrous engine size now at my disposal!
Think of it this way: you've increased the size from 60mm to 62mm in two directions, not just one! (left-right and fore-aft...) So, you have to multiply it twice.
There's one direction left: up/down. Your PB has a swept distance of 83mm, which is exactly the same as your PA. That's set by the crankshaft...