VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc The Rocker Arm, to bush or not to bush???

1929-31 ALL gp. 0.334, pn. 835668 Bushing, rocker arm.
Note: Rocker arm bushings not serviced after 1931.

This is the entry from the 1929-1950 parts book for the rocker arm bushings. I see a lot of posts mentioning bushing kits and installing bushings for later engines, yet last year when I did my valve job on my 1950, 216 and cleaned up the arms there were no bushings in those arms. Just exactly when did they make the switch over to steel on steel?
Denny Graham
Sandwich, IL

Ok, I just re-read the parts book and I see that 1940 was the last year for the rocker arm with the bushings. So I guess I got my "learn something new every day" exercise out of the way early today.
But I'd still like to hear about the bushing kits. Although GM quit replacing the bushings in ’31 I’m assuming that the aftermarket jobbers filled the gap? And that replacement bushings could still be pressed into the rockers? Which brings to mind the possibility of re-boring the later rockers once they have gone egg shaped to take a bushing. Is there anyone doing that yet?? I made a simple fixture that held the rocker bore parallel to the belt sander surface and re-surfaced the valve contact surface, which worked out real nice. Luckily the bores and shafts in mine were not worn much but I don’t see why re-boring them to take a bushing would be a problem if the need ever arose.
Denny Graham
Sandwich, IL

`Yes, the 1941 was the first to have the "bushingless" rocker arms. In looking back they actually had less of a wear problem than the brass bushing style. The only only time that we ever replaced them is when the rocker assembly was run dry due to the oil passage plugging up on the later 235's.
This is the description of the new advancement from the 1941 Engineering.

Their material is the newly developed ArMasteel, a special semi-cast steel having unusual wear resistant properties that make possible the elemination of the bronze bushings. Instead the arms are diamond bored to operate directly on the shafts. After boring they are granodized to protect the bearing surface against scuffing or scoring when operated against the hardened rocker arm shafts.

I have never seen bushing made for repairing. See no reason why they couldnt be "rebuilt" using the 1937-40 bushings.

granodized???
That's a new one, worked around machine shops a good portion of my life and taint heared of that heat treating pocess.
I guess I've had pretty good oil to my rockers cuz there wasn't much wear at all.

DG

"graanodized" refers to a coating. I would bet it is like the tin Chevrolet plated the cast iron pistons with from 1935 and up.
Luthy brand piston rings advertised that they were "granodized" to assist break-in. Have see n it mentioned as being used on other parts also.
The granodizing looks like a black powder coating. In the high friction areas it wears away and helps to form a super smooth wearing surface.