Well, given castor the pistons didn't looks as good.. and the rings has lost some mobility and started to stick. The skirts on these pistons where not coated either. That black color is castor varnish.
Yeah , thats typical vegetable sheen as we to referred to it as . Even with Benol it accumulated , during extreme oval short track racing applications . We tore engines down every week , proper tune helped . However the only engines that were less effected , were the long distance Enduro sleds were the thermal cycles were reduced and extended high temperature runs effectively burnt off any residue effectively or our Drag sleds which ran short duration but extremely hot . Short duration (lap) varing heat cycles , just continued to built up & accumulate deposits on the crowns , rings & eventually exhaust ports. It was what it was , prefer today's cleaner oils !
