Rocker shaft oil pressure.SP250.

[Brianstaples]

I've found the oil pressure in my rocker shafts ,is exceptionally high, at tick over (500rpm) engine hot oil pressure,is60psi on my dash board oil gauge, I have made and fitted two oil pipes, one on each cylinder head,to rocker shaft bungs,in the opposite end to inlet oil pipes.the oil is then piped into rocker box covers,reducing the pressure in the in let rocker shafts. At tick over now my oil pressure one dash board gauge is(30psi).now my car at tick over dose not blank out the cars behindwith smoke.I fitted inlet valve guide,and this greatly reduced smoke emissions,but not completely.now smoke free ,I would like a permanent,solution, ie,restricting oil to rockers from engine.any ideas any one.

[Chris_R]

This sounds more to me like a problem with the oil pressure relief valve. The oil pump is designed to pump far more oil around than the engine can actually use. Most of that excess volume simply goes out through the pressure relief valve. The pressure that you are reading is the measurement of the resistance to flow of oil around the engine, most of that pressure comes from the resistance from the crankshaft bearings, a certain amount from other outlets. By opening up the outlet at the rockers and allowing more to flow you are potentially reducing the flow to the bearings.

[tjt77]

confrm the dash guage is reading correctly by substituting another guage .. if its IS as high as you suggest, then most likley the oil pressure relief valve has stuck closed and needs to be freed up.. as long as the rocker assy is clean inside and out and installed correctly then there should be nothing more required regarding oil pressure issues..rocker gear is not subject to high oil flows or restrictive enough to effect oil pressure providing its all 'as it should be'..

The smoke could have several sources.. if valves/ guides are to factory tolerances.. then the smoke is probably due to piston/bore wear issues .. or if no obvious wear is present on removing heads, may simply be the oil rings and their drain holes in pistons are choked up ... to resolve 'lower end' issues such as removing pistons and rods for clean up and inspection will be time consuming.. single piece cast iron oil control rings are not very efficient ..its best to upgrade to an aftermarket multi piece oil control ring if you have it apart.. I have a preference for the now defunct 'Cords' brand (still plenty of old stock out there) ..these were designed to be used on pistons with wear and bores slightly comprimised as an 'interim' overhaul ..but they last a LONG time .. Ive got about 70,000 miles on one engine I fitted them too..and still good compression and minimal oil consumption...the current 'deves' brand are also very good, but they need hard break in in order to seat properly.. the 'hepolite apex' rings are also good and designed for lightly worn engines as per 'cords'.. again..still a good amount of 'old stock' out there if you look..