G'day all, my brother is rebuilding a WLA engine and these pistons come out of it. Just out of curiosity, does anyone know they are from? The manual shows the pistons with all rings above the pins, but these have the oil ring at the base of the skirt. Can't find any info on this style anywhere. Thanks, they are going in the bin anyway. Bob.

Not 100% sure, but I have seen similar looking pistons from an old hot rod that was running a V8 Ford flathead. It also had oil rings below the pin just like these.

very interesting...

https://www.hemmings.com/stories/article/three-ring-circus

Old Ural 650s had 4 ring pistons, the low compression pistons any way. The higher compression later pistons, which can be dropped into earlier motors if you're brave, are 3 rings. Got a nagging feeling that Guzzi Ambassadors had 4 rings too, but might be rong.

Turns out they were made by a Melbourne company called Polson Pistons. The company was last heard of in the 1960's.

Just out of curiosity, are they anywhere near standard bore or has it been punched out?

And just for fun, extracts from Polson's bike piston catalogue from the 50's, but because of my Norton background, the selected page is for their Norton range.

The barrels measure 32 thou over, so I say at some time it was taken out to 30 over and then 2 thou wear. The pistons, though, were 20 thou smaller than the bore, so there was a fair bit of wobble when we took it apart. It will be going to 60 thou over with pistons to match.