I removed, painted, then reinstalled this very small pipe plug in the head of my ‘54 235. When I finished tightening it I asked myself, “Why is this here?”. Was there something attached to the hole before? Pipe plugs usually fill in a hole used for something, so I’m curious about the hole.
Chuck 1950 Chevy 1/2 ton (all original) 1951 Chevy 1/2 ton (future streetrod) 1941 Chevy coupe 1938 Chevy coupe streetrod
It's probably how the oil gallery was drilled. It's kind of hard to make a drill turn and drill at right angles. The factory then taps the hole and plugs it so the oil doesn't leak out.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
That external line was added if the oil gallery from the rear cam bearing area got clogged. That was a common problem on the full pressure 235's which resulted in the rocker arms losing lubrication. The other end of the line got plumbed into the driver's side main oil gallery that supplied the oil pressure gauge and the oil filter. The original intent was to provide two oil passages in the head that intersected at a 90 degree angle to lube the rockers when the under the pushrod cover line was eliminated in the late 1950's. The end of the sideways hole was plugged with a 1/8" NPT plug. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Now, I find that interesting! I rebuilt a 235 “splasher” from a ‘53 sedan and my retired mechanic consultant said he wasn’t satisfied with amount of oil reaching the rockers. So he drilled a hole through the top of the head, ran tubing from the opposite side of the block and plumbed it to the rocker arm tube.
I thought he was just being creative, but he evidently had some lingering remembrance of this problem and solution.
The head is drilled vertically from the deck up for the rocker feed but is not drilled all the way. The path takes a horizontal path. So the head was drilled horizontally from the side to crreate that path, then threaded and plugged. Fortunately for us GM did it this way because when the motor wears a bit after a bunch of miles, or the line behind the lifter cover gets clogged on the 54-57 motors, you can use that threaded port as an external oil feed to the rockers. Happy coincidence I guess!
I have a 1962 235 in my 46 COE and I used that 1/8 pipe thread at the top center of the head and hooked it up to my original 46 oil pressure gauge. It reads right in the middle of the factory gauge 15. Then hooked my after market gauge to the block that reads 40.
I have a 1962 235 in my 46 COE and I used that 1/8 pipe thread at the top center of the head and hooked it up to my original 46 oil pressure gauge. It reads right in the middle of the factory gauge 15. Then hooked my after market gauge to the block that reads 40.
At least one of them is wrong.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
