Most - but not all - pistons for the A Series are measured 1/2" up from the bottom of the skirt, 900 to the Gudeon Pin.
Check that you still have the original pistons (maybe post up a Photo).
I measured it : I can not insert the 0.05 mm gauge
Let's just back up a bit here.
Given that it is a worn bore and used pistons, it's fairly safe to say there's well enough piston to bore clearance here, but you'd check after having the bore honed.
I'm also wondering if you are trying to gauge if the engine needs a rebore based on these clearance numbers ?
Honing is a micrometer scale process, I think it will make a very little affect on the measured numbers. First I'll will take the block to a machine shop for honing. I measure again and I'll see what to do next.
Haynes says that measure the bore on top and bottom. Rebore is necessary if the difference is more than 0.152mm (0.006").
Does Haynes mistakes ?
Edited by gaspen, 18 September 2019 - 06:43 AM.