try this
where i work we build many wisota legal 2bbl dirt 350s. depending on class they are solid or hyd lifter, with stock rockers and single spring. with careful setup this will runup to 7200 or so with good relibality.we did have some issues with top end oiling. rocker arms were turning blue, getting hot. to get to the bottom of this we took a steel valve cover and cut the top off. then welded a sheet metal tube a foot tall to it. on the dyno you could see where the oil was going maybe, then i grabbed the timing lite. by turning the advance dial or switching the pick up to a diffrent cylinder you could see everything. every drop of oil, where it came from, and where it went. we found rockers dont allways squirt straight, and some lifters flow more oil than others. now we could make choices based on fact. by careful parts selection we were able to redirect the oil flow to the rockers. this allowed us to use a lower psi oil pump=more power. springs and rockers are a splash lube deal. oil flow will be determnend by how hot it will get and how long the race is. do not restrict it any more than nessary let some one else try the .050 hole. we dyno with system one screen filters, and use wix race filters. get an oil filter cutter and cut open every filter that comes off your motor! stickboy331