As pointed out, the oil supply to the top end could be interupted due to sludge buildup. Reasons are lack of oil changes, a plugged crankcase breather system & in some cases long term operating the engine with a broken or non existent thermostat. Also, our moderator Ted has indicated that in long term service sometimed the center Cam bearing wears enough that it cuts off the supply up to the Heads. One area that is likely be stopped up, is the  2-1/2" offset passage at the top of the engine block deck, needed to align with the Head oil passage to the rockers. Some people have tried various methods to clear it, including removing the rocker assembly & poking a wire down thru the oil supply hole, followed by using an air compressor. If the oil supply is much worse on one side than the other, I believe  that indicates it's likely a worn cam bearing. (I might be corrected on that point ?) Good luck if you decide to try aleviating the issue..        


Paul

Does the system work....as in...does it oil the overhead without starving the main and rod bearing in the engine.  There were some that used a small orifice through two head pan studs that was to ensure that not to much oil pressure was lost to the rest of the engine.  If yours works fine and there are no issues.....leave it alone.  Overhead oiling is a big subject with y-blocks.  Be careful when changing something that works.  Seems like most people don't even want to discuss the subject.  LOL  Look on you tube.  Good luck.

Thank you for the info.

Back in the day, that was the quick fix to get oil to the rockers when the internal passages were getting blocked with sludge.

Does anyone have any idea on why my 1959 ford custom 300's 292 y block has external oil tubing for the valve covers?