Originally Posted by
Recycled Flyer
And just to confuse things even more this very good Aussie engine builder has indeed devised his own design contra pistons that install from the top of the liner!
http://www.modelenginenews.org/~mode...tml#DCO_CONTRA
But they do seem to be unique in that ability and unlike a
ST G 20/.15D.
Sorry gents, but I think you're misunderstanding David's process for making and fitting contrapistons. The contra is NOT installed from the top of the liner, as you assert, Chris. What the article is referring to is that the tapered, thin-walled contra is checked for fit by being inserted (not pressed) into the top of the liner. If it will enter the bore for a certain distance without jamming, then it's the right size. It can then be installed in the usual manner from the bottom of the liner. It's a very clever method that seems to pretty much guarantee a good result.
The article possibly gives the wrong impression by saying, "It can now be thoroughly cleaned and pressed into the cylinder top". Yes, it is being pressed into the cylinder top (because that's where it resides) - but it's being pressed in from below.
Hope that clears things up.
Steve