The Stovebolt Site Forums The Shop Area Engine Shop Chevrolet 235 rocker arm bushings?

Where can i get bushings for the rocker arms on my chevrolet 235? Are there any companies that just specialise in making parts for these engines?

Oldtruck1946,

I didn't think there were any bushings involved in the rocker assembly. The rocker arms are cast or forged steel running on a steel shaft, that's it!

When the shafts wears out you replace them...when the rocker arms wear out, you replace them.

Stuart

I have a set that has bushings in them.

btt

Not only do some have bushings, there is evidently more than one type.
I've read some of the parts listings, and cannot make sense of what change occurred when on rockers (and the references in 1955-* lists to "Corvette and all", meaning V8, don't help!).
Anyone have a good time-line for changes?

I have never seen bushings in rocker arms. What I have seen is wear marks made by the spring that makes it appear there is a inserted bushing when there actually isn't, but I have been wrong many times before.

Stuart

I can't find any reference to any such animal in the Master Parts Catalog. I wonder if this might be something engine rebuilders came up with as a way to save time and money???

I know my '58-'62 261 with solid lifters has bushings, but my '55 235 with hydraulic lifters does not.

Somewhere in my cave of forgotten tools along with a GI Ring Tool and a 216 oil pan targeting tool is a rocker arm jig block that held the rocker while it was bored oversize, a bronze bushing pressed in, and then a slightly undersize ream was run through it. It was then taken over to the Sunnen rod honing machine and honed to the rocker shaft size. New parts were nonexistant during WWII so there was much building up and grinding back, turning over to an unworn side, patching, sewing, vulcanizing, you name it. It was in this era that some unique machines and processes were invented. As said; necessity is the mother of invention.

Hey panic,

What is the Group and part number for the bushings.

Are the parts listings online?
If so, provide the address and someone should be able to "make sense" of them.

The Group number for rocker bushings is 0.334. Chevrolet only sold bushings for 1929-31 rockers, after that you had to buy rockers with bushings included. Although many rebuilders installed bushings to repair worn rockers, my experience is they were only used buy the factory until 1940.

Pre '68 Dave;
Can you link to the page that shows Group No. 0.334?

The two online catalogs I have access to don't list that group no. at all.

Thanks

If you look at 0.333 Valve rocker, you will see that 1941 says no bushing, so I think this confirms what I said above.

Yup, no mention of either bushed rocker or separate bushing after 1940, in fact the 1954 specs say for "bearing type: machined in rocker arm".
Does that mean that all later factory rockers (especially 1954-63) with bushings were rebuilt?
Boring the rocker body out to accept a bushing might have been normal practice back in the day, but it makes me nervous.

In my experience the shafts always wore out long before the rocker arms did. When a person replaced the shafts, the logical mechanical solution would be to replace the rocker arms too!

My bet would be a new rocker arm would be much less expensive than having an old one bushed and having the end ground too.

Stuart

An old Sioux valve grinder at a school shop where I taught had accessories for re-contouring the bottom of valve lifters, and refacing rocker arm tips. We seldom if ever used them, other than showing the students how they worked. I think those types of operations fell out of favor as labor costs got too high to make them practical. My father used to charge $65.00 labor for a ring and valve job on a 216, and he was among the higher-priced shops in the area.
Jerry

Dave, thanks for the info and the Group #.

Here is the Bushing 0.334, in the 54 catalog.
Bronze - 3/4 I.D. x 25/32 O.D. x 15/16 length
http://chevy.oldcarmanualproject.com/1929_54chevyparts/00/104.HTM

Also, note Arm, Valve Rocker 0.333,
1929 thru 1940 w/bshg.

Looks like that bushing is way too small for the later engines:
the .781" bushing OD is smaller than the .791" late shaft.

I looked around to see if there were some common pin bushing that might work, but most have at least 1 dimension off. Looks like the closest common commercial size is a 7/8" × 1/16" wall tube = .750 ID, ream or hone to .792" (or whatever cleans up your rocker).

Jerry, funny that you should mention that, I used one of those when I helped out in the machine shop at the auto parts back in the early 60’s. When I did my valve job a couple of years ago, lacking that Sioux equipment, I made up a small base plate with a perpendicular boss that fits the bore of the rocker. I have one side of a bench grinder equipped with a 3M Scotch-Brite rubber bonded finishing wheel. I simply square up the tool rest on my grinder, place the rocker arm over the boss on my fixture and slid it across the wheel in an arc to radius the contact surface square to the bore. I’ve got the fixture around here somewhere but can’t find it right now. Here is what the rockers looked like before and after. http://www.pbase.com/dennygraham/image/121940017

As far as re-boring a rocker arm, I would think that would be a rather difficult task. The bore is the datum for both the other features to reference to. During manufacture I’m sure the bore was machined first or used as Datum ‘A’ for you GD&T types. Then the thread for the adjuster and contact surface was machined in reference to that. To reverse the machining process you would have to find a surface that would locate the bore inline with the machine axis before you could re-bore it. The only feature that you could use to reverse machine them with would be the adjustment thread. In other words, I doubt very seriously that rockers that didn’t have bushings originally were ever re-bored to take bushings.
Denny Graham
Sandwich, IL

I'll agree that losing the reference point is important, and that wear in the shaft opening is always eccentric, and typically located between 4 o'clock and 8 o'clock.
However, only fairly extreme wear will significantly affect rocker operation.
If the wear is .030" (the ID is now .822", very sloppy), the centerline error is only .015".
If the ID is simply enlarged concentrically (viz., no attempt to correct the alignment) to accept a bushing, the new fulcrum position will be too low by .015", raising the rocker on the shaft by .015".
If the rocker is adjusted normally, the long (valve-side) lever will be angled down by .42° (less than 1/2 of 1 degree) and the pushrod adjustment will be longer by .015" (shaft error) + (valve error ÷ 1.477), or .025". This is exactly 1/2 turn on the tappet adjuster.

In my opinion, although this permanently changes the rocker's geometry by changing the delta angle of both levers, this is not only harmless, but within the range of normal error due to wear and stacked tolerances.

Re-facing the pad, although obviously necessary, also changes the geometry by moving the long lever's angle upward, but again the change is almost undetectable. Taking off .010" to get a clean surface is about .3°. Unfortunately, it's added to any shaft center error.
The combination of wear patterns tends to identify rocker as suitable for rebuilding, or not. If the shaft hole ID measures more than +1/32" (top to bottom) and the pad surface is rough - use another rocker.

BTW: if anyone has 1954-* intake rockers that are too bad to re-use, I need some to cut up for research, happy to pay the postage and share the results?