grinding stock rocker arms

simon

simon

Famous Member
got myself a used set of adjustable rocker arms, supposedly in good condition.

Bought unseen, and much to my dismay, they're all worn a good .010-.016 at the tip. wear clearly was caused by a lack of lubrication.

generally, replacing worn rockers is considered the better way of dealing with such problems, yet new rockers are somewhat hard to come by in this part of the world.
So I'm thinking about saving the ones I have, grinding the tips, shot peening and maybe carburizing.

The chebby-wrenching 'nam vet in our shop and his fellow who worked for Lycoming in the 70s said it'll never work, since it'll change geometry completely.

On the other hand, oldschool hot rod buddy with an '38 ford sedan and even more experience than the Lycoming guy says as long as they're kept in their place with their corresponding valve and pushrod, it'll work out ok for a stock rebuild.
In case I wanted to grind, he suggested to check valvetip and keeper clearances real good. He also recommended backcut valves especially with decreased rocker arm ratio.

what's your opinion?
 
Howdy Simon:

Here's a source for individual rockers. <www.rockerarms.com/>

Usually it is only the front ones that wear badly due to lack of maintainance. They are the last to get oil on cold starts and the 1st to plug up.

I'd be reluctant to grind the tips. It may case de-tempering and/or cause brittleness. Neither are good.

Grinding the tips will not change the ratio.

If you do try the grinding solution, be sure to check - before start up- that the rocker tip/arm does not come into contact with the keeper, retainer or spring. The rocker valve tip should center over the valve tip through its complete motion. Anything else and you're asking for trouble.

Make sure both oiling holes are open on each rocker. From the front of the engine there is one on the valve side at about 10:00 o'clock. The other is on the adjuster side at about 3:00.

Adios, David
 
There is, or was a machine made for this purpose. There are also atachments for valve grinders for this. They should only be trued up. They should not be ground alot. I heve no idea how much is too much.
The key to doing a good job is to get the curve right. The rocker travels in a curve and the tip should roll across the surface not slide. If the rocker slides it will side load the valve and wear the guides.

Check and see if there are any industrial machine shops in your area. They will be familair with this type of rocker.
 
People here just used to linish them, without removing from the shaft. A bit rough, but as the linish marks were across the face (90° to the rocker's wear pattern) it broke in like a new part.
 
A long table, wide belt sander with a fine belt. Also used on exhaust manifolds and cheap head resurfacing.
 
addo":o3eij5wy said:
A long table, wide belt sander with a fine belt. Also used on exhaust manifolds and cheap head resurfacing.
Click to expand...

Hmmm, In millwork it's known as a vertical sander, or vert belt...
Wow, cheap shops surface heads with those? Gee, 80-grit or 100?
Scary...

Mike. <---(Used to be a millworker, then got sucked into the white collar abyss)
 
If you know what you're doing, they can be pretty effective. A light touch is part of that recipe. Heat buildup is less than for grinding wheels. Most linishers in metal shops lay flat, rather than upstanding. Some can be tilted up to 90° while the job is held on a table in front of the belt.
 
I'm rebuilding a cylinder head from an `82 200 and just completed refurbishing an adjustable rocker arm assembly from an earlier engine to put on it. I bought a new rocker arm shaft, unclogged the oil holes on the rockers and drilled the one pointing toward the valve to 1/8". There is some wear on the tips but not enough that I'm going to replace them. I plan on putting the most worn rockers to the rear of the engine.

I also noticed a couple of things. One is that the rocker tips don't touch the valve tip in the middle. They touch a little off center, just a bit closer to the pedestal side on each pair. David mentioned the rocker tip should center over the valve tip but there doesn't seem to be a way to adjust them.

Also, there are numbers stamped in the rockers on each side of the end where the adjuster screws in. They are all different from rocker to rocker and also on each side. They are numbers such as 125 - 45, 122 - 138, 58 - 141, 184 - 192, etc. What do these numbers indicate? There's also "GA" stamped on the valve tip end.
 
Howdy back All:

Kelly- there is a slight amount of adjustment by lossening the four pedistal bolts and pushing the whole assembly in the direction needed. Then with continued gentle pressure retighten the four bolts.

Also the rocker tip walks across the tip of the valve as it rotates through its cycle. The rocker tip does not stay in the same contact place on the tip of the valve.

Adios, David
 
The problem with moving the pedestal one way or the other would be that if you pushed it enough to center one, it would put the other right on the edge. Here's a photo of the assembly (maybe from a `61) on the `82 head I'm rebuilding. This position is consistent on every set. The last photo shows the wear marks from running on the original engine. They are also consistent from set to set.

rockers1.jpg


rockers2.jpg


I'm just wondering if it's really that critical on a stock engine? I may pull the valve cover on my current engine this weekend just to see if it's the same situation.

Also, I emailed the rockerarms.com site about rocker arms and they said:

"We just sell the assembly. The cost is $101.50 plus shipping. These are rebuilt arms with new screws,and bronze bushing installed. The rocker shaft is hard chrome plated."
 
update:

after some cleaning and proper measuring methods, things don' t look so bleak after all. No shrink holes, no cracks, just common wear and lots of carbon buildup.

Rocker arm bore wear measures .002" (wear limit is .006" , so I`m not even bothering about bronze bushings), the rocker arm tip wear turns out to be less than initially assumed - .0048" at the most.

Addo's advice works perfectly. I`m doing it all by hand using 180- and 400 grit abrasive cloth.

I have some new questions though: Other than a thorough cleaning, what should be done to the adjustment screws? May I blast them with glass beads?

Do the ball ends benefit from heat treating, nitriding, a hard chrome plating or some other surface treatment like that?

Threads are less than perfect compared to the threads of, lets say, ARP bolts. Is that something I should worry about?
 
:D Many years ago,a friend had to refurbish some rocker arms from a foreign car.No new one were available to him at the time.What he did was to silver solder new metal to the rockers and then ground them back to original specks,and then polished them to a mirror finish.That vehicle is still running today with no problems.
Leo
 
I know a guy who has added material by metal spray and then re-machines and re-heat treats. Kind of spendy to do.
 
You must log in or register to reply here.
Back
Top