Cylinder Sleeve Nuts and Piston

[KerryAJS]

Hello All
I have started to strip my 1963 350 engine and I'm looking for information, please.
Firstly, when the engine was rebuilt over 40 years.. that sounds like a long time ago when you write down! ..we replaced the piston with what I always thought was a high compression piston and from memory seemed a taller piston. I was under the illusion that the export bikes had a lower compression piston fitted?
Anyway I have attached a picture of the piston I have now with the oversize number H 020" and part number 028109, which comes up as a standard oversize piston, so was there such a thing as a low compression piston?
My other question has to do with the cylinder studs, one of them seems to have been machined shorter.. any ideas? Also when checking the head sleeve nuts for measurement on the cylinder studs , two of seem to bottom out before they can tighten on the head, it just a case of fitting thicker washers? The head does look recessed where the sleeve nut contacted it.
Thanks for any answers

[Reynard24]

The piston that was in my '63 G3 is much flatter and has the number 028127 on the top.
Rumour has it that Russell Motors sold these lower compression pistons in the 1980's as original spec ones were not available and it is further rumoured that these flatter pistons were for trials use. The club sells new pistons for the 74mm bikes and these are "lumpy" like the one in your post.
The flatter piston was ok for pottering around but the engine ran out of steam at around 65mph, the correct piston cured this and gives much better acceleration and top speed.
With regard to the studs and sleeve nuts, all of mine were the same length but I did run a die and tap down both to clear the threads which had a liberal coating of Wellseal on them. The head is not recessed but, like the long-stroke heads, does tend to collapse particularly on the exhaust port side - mine was ok but I have heard of heads being ali welded back to the correct profile or use hardened washers. From memory the washers were pretty thick anyway.

[KerryAJS]

Thanks Reynard24, very helpful information. Looks like I have the correct piston!