One more suggestion, and I had to learn this lesson the hard way- - - - -a smooth layer of carbon builds up behind piston rings as they wear. Unless all the carbon is cleaned away before installing new rings, the rings squeeze down on the carbon layer and dramatically increase the drag. Take an old, dull hacksaw blade and carefully scrape all the carbon away down to bare metal at the bottom of all the ring grooves. A broken-off old compression ring filed to a chisel shape also makes a good carbon scraper.
Jerry
