Inliners International Forums General Discussion Engines Oil Pressure - Rocker Arm Assemble

Here is what I have always understood. The 55-57 235 uses the rocker arm connector that loops over itself and dumps excess oil onto the head. The 55-57 motors received rocker oil from a steel line under the tappet cover that pulls oil pressure from the rear cam bearing to a fitting under the cover about the middle of the head. You can see about where this is by looking for the bulge in the cover. This line is notorious for clogging up and starving the feed to the rockers. Lots of owners, when flow was impeded a bit would pinch off the copper loop on the connecter to attempt to keep all of the oil possible going to the rockers. Eventually the line would clog up completely and then you would use an aftermarket external oil line kit to run oil from the driver side of the block
at the oil sender unit, to the square plug on the side of the head which is a direct feed to the rockers. The above may also apply to the 58 motors but I am not positive. For the 59 and up 235 motors, chevy made a slight change in the rocker oiling system. Those blocks do not use a steel line from the rear cam bearing but draw oil from the main galley center bearing up through a drilled passage in the block tonthe head. Gm also enlarged the the size of the feed in the head and used a connector that was pinched off from the get go. This provided a more pressurized sealed system. Gm also altered the rockers so that the higher pressure would not spray oil way over the rockers and springs
instead of the oil running out the rocker spit hole and lubing the rockers, adjuster balls, and springs. They did this by moving the oil grove inside the rocker arms. So if you look at a 55-57 rocker arm, the grove intersects the oil spit hole. On the 59 and up, the grove is offset and does not intersect the oil spit hole as a way of maintaining a little pressure and keep good oil to the rockers.