3.4 litre engine numbers

[thom.hale648]

I've just acquired two engines, that I believe are from XJ6's
both are 3.4-litre
they have engine numbers 8A14723-H and 8A6366-HZ
I've done a bit of digging around on the tinterweb, and failed to find anything that allows me to confirm what vehicles these engines came from or anything about their specifications
8A6366-HZ has cylinder bores spaced as per 1960's 2.4's, 3.4's and 3.8's (two groups of 3 with a bigger gap in the middle)
I don't know about 8A14723-H yet because I haven't got the head off...
Wikipedia says that the "new" 3.4-litre engine has the same bore centres as the 4.2... I'm struggling to believe that this can be true, because I believe ALL heads have 83mm-diameter combustion chambers on the original spacing of two groups of 3 - so why on earth would Jaguar have built an 83mm bore engine on 4.2 bore spacing? The head combustion chambers wouldn't line up with the bores and it WOULD matter because the cylinder bore is the same size as the combustion chamber...

So -
1) can anyone confirm which cars my engines actually came from?
2) has anyone got any information about the specifications of these engines (compression ratio, camshaft profiles, camshaft timing etc)
3) what do the -H and -HZ suffixes mean?

[mike020150]

Here are some of the more obvious answers to some of your queries. 3.4 litre engines from XJ ser 2 cars have the 8A prefix to the engine numbers. They were indeed based on the offset 4.2 litre bore spacings and Jaguar didn't alter the cylinder heads to suit! However, that didn't seem to matter in practice. Compression ratios were variously 8.4:1, 8.8:1 or 9.0:1. Valve lift was 0.375". Mike.