As I move very slowly toward getting this engine running, I have come across a damaged thread on the #6 exhaust valve rocker arm.
I have chased the threads and they work smoothly, but I am wondering if I would be foolish to reinstall this piece.
In the MPC it is listed in Group 0.429 as Screw, Valve Rocker Arm Adjusting, Part Number 837385. (If I need to replace it, is there a new part number for a replacement part?)
Supposedly the engine is either new or was rebuilt. It certainly looks clean inside from what I have observed...but what would cause this type of damage to the threads? Is it possible that they were just defective from the factory?
Thanks, Nick
Nick 1940 KC Model 1/2 Ton Pickup Project (with '37-'39 Bed and '46 Frame) Taos, New Mexico
Shoot me a PM- - - - -I'll send you a handful of them. Somebody has overtightened the jam nut during a valve adjustment. New adjusting screws and jam nuts can be purchased from Smith Brothers in any size and shape you can imagine.
"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!
Those screws are hard, not prone to galling damage. It looks like an insignificant portion of it has either got chipped off, or is a manufacturing defect. Since your lock nut runs smoothly on it, I would not hesitate to use it as is. That would be a better choice than replacing with an aftermarket one, or one from another engine which may not have as nice of a ball end as yours has.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
Nick - Here's a source for NOS ones if you don't take Hotrod up on his offer. Pushrod adjuster GM# 837385. There are no newer part numbers associated with this item per a quick search of GM Partswiki.
Note: The picture on the web page is weird as it is distorted for some reason. It's the correct part, just looks odd in the picture.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
I will weigh in a little here. A few years ago I installed a nos replacement Sealed Power rocker arm set on one of my 261 motors, and a set of NOS TRW replacement push rods. What I did not do, mostly because I have never had any issues, was blue up the cups and balls with Dykem and work them in by hand to make sure the ball was fully seated in the pushrod cup. In this case, they were not with the adjuster ball being ever so slightly larger than the cup and so the ball was partially seated with the majority seated on the rim of the pushrod cup. And yes, you guessed it, broke the cup on the pushrod after about 100 miles.
So I bit the bullet because I just don't want that kind of hassle these days so I ordered a set of Smith Brothers pushrods and adjusters. More expensive yes but here is the thing. They will not bend, they are straight as an arrow and the ball adjusters and cups are machined to very tight tolerances for full seating. They are really great quality. I can be pretty hard on my motors and this particular 261 is no exception. I can report not a single hiccup in 10 years.
Here is the other thing, their adjusters use a hardened hex adjuster and hardened multipoint adjusting nut which means you can use a standard small block Chevy rocker adjuster tool that will not slip off like a screw driver. Makes adjusting the valves a little more comfortable.
Otherwise, I am with 52Carl, if the adjuster nut is running smoothly, use it.
