From: Barry Lovelock
Date: 29 Jul 2002
Time: 08:40:19
Remote Name: 194.168.74.12
Basically, 4 ring pistons are/were often used for "touring" purposes. They generally give better oil consumption (do the 3's have an oil-control ring?) and of course compared to the 3's, have more friction and hence waste power. Conversely, the 3's, are used for more sporting purposes, where oil consumption and hence smoke may not matter.
Now, if you were to ask how many rings "moderns" have, I wouldn't know, but we're talking A7s here.
In all the A7 engines I've built, I always used the 4-ring JP ones. However, if I ever rebuild the Ulster, I will use John Sutton's "Works" slipper ones and they are 3 ring with an oil control, see: http://www.motorsnippets.com/cars/austin_seven/520.asp
Barry.