i posted some of this on a thread comparing 60 & 80lb oil pumps. but i'll include it here as part of my engine building specs. in the old days, nunzi & H-O were the only pontiac guys i knew about. read where H-O said 60# was needed 2 overcome the centrifical force of the oil already in the large mains of the 455 at 6000 rpm(obviously not an exact quote) so i assumed this info 2 be accurate & ordered an 80# spring & cup kit for my melling pump. later on i decided 2 just shim the 60# spring & save $. worked just as good. some recommend .060 shim--thicker shim=more press. many now talk ugly about 80# press--infering that many parts will suffer premature failure with more than 60#. many say 60# is plenty if every brg clearance is exactly correct & if the oil viscosity is exactly correct for the clearances used. maybe thats why some shops get 12 grand for a mild 455 crate motor--gettin all those clearances exactly correct--you think? if you've got the $--buy it! for the rest of us--i'll tell you what i did. if the brg & crank looked good, i just put new brgs in it, along with a 500 caddy rear seal(for big journals) & bolted it in. if the journals looked bad, i bought a reground crank/brg kit & bolted it in. either way--who knows what the clearances were? so for a little ins, i ran 80# press, 50wt racin oil & a can of stp (the thick, slick, gooey stuff). & lo & behold it worked--never lost a 455 drag motor. either just lucky or blessed i reckin!
