Prior to 1958, "Lubrication to the valve mechanism is supplied by a drilled passage from the rear camshaft bearing to a pipe located under the push rod cover to a fitting at the top of the cylinder block. The oil then flows through a passage drilled in the cylinder block and head to the valve mechanism oil connector pipe between the two hollow rocker arm shafts, then distributed to all rocker arm bearings. A bleeder hole in each rocker arm supplies oil for lubrication of the valve stems and push rod sockets."
In 1958, the blocks of the 235 and 261 engines had different oil passages cast in them (than in earlier years) to allow oil to flow from the rear and front cam bearings through the valve-lifter journals to a hole cast in the center of that side of the head. The passage in the head runs below a head-bolt and up to a "oil delivery" hole in the top of the head. The oil connecter in the rocker arm assembly has a tube that is inserted into the "oil-delivery" hole in the top of the head.
In 1959, the "plumbing" of the oil line from the lifter-journals to the rocker arms changed to allow more oil flow and to maintain higher pressure in the internal oil lubrication system.
Figure 12, directly below, is of one side of the rocker arm assembly. The part at the left in Figure 12 is both the oil connector that connects the two sides of the rocker arm assembly and it is the oil feed pipe that is placed into a hole in the head. This style of oil connector was used prior to 1959. Note that there is an overflow outlet-pipe that goes up out of the oil connector and then is bent downwards, to drain through an oil return hole in the head.
compare the above photos to the 1960 assembly 1948-51 1954-57 1958 1959-62
Prior to 1958, "Lubrication to the valve mechanism is supplied by a drilled passage from the rear camshaft bearing to a pipe located under the push rod cover to a fitting at the top of the cylinder block. The oil then flows through a passage drilled in the cylinder block and head to the valve mechanism oil connector pipe between the two hollow rocker arm shafts, then distributed to all rocker arm bearings. A bleeder hole in each rocker arm supplies oil for lubrication of the valve stems and push rod sockets."
Drilled 235-261 Head bolt: the information below is from Pre '68 Dave's Blog, a member of Stovebolt.com.
From 1938-62, only two head-bolt part-numbers are listed for 216, 235 and 261. Long and short except for a special drilled bolt, used when a 59-62 block is used with earlier top end* to reduce the oil flow to the rockers.
Note: Use with drilled bolt
Plug # 37 64 579
Install in block oil port near right center head bolt.
(This plug blocks the original oil path and sends it through the drilled head bolt)* The cylinder head did not change but the rockers did.
1948-52 1953 1954-57 1958 1959-63
rocker-arm assembly lubrication
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lederman@siena.edu
www.1954Advance-Design.com
