Tuning Posh pistons

[Toshi 975]

Just got these 650 pistons. The crowns have been recessed to clear the valve heads in the event of a skimmed head. Skirts are grooved. Not sure if that is to reduce friction or retain oil for better lubrication or both. Intend to use the in my next interesting engine build.

 

[the hobbler]

Hell's teeth David! You would have to skim a great chunk of a cylinder in order to utilise thes fully. Wonder what sort of compression ratio you would arrive at.

 

[Toshi 975]

Hell's teeth David! You would have to skim a great chunk of a cylinder in order to utilise thes fully. Wonder what sort of compression ratio you would arrive at.

According to the guy I got them from you can go up to a 5mm skim which is a bit extreme and I certainly would not go that far. They did come from a specialist race/rally/tuning engineers in Poland so I assume they knew what they were doing but like some of the Italians they did some extreme things. I am thinking of a 2mm skim.