powdered rocker ball broke

[Clem Z.]

Re: powdered rocker ball broke

Out of curiousity I called Crane to see what their high dollar Nitro-Carb rocker arms use for pivot balls. The rocker arm pivot balls are grooved BUT they are heat treated powder metal as well.

i could be wrong but i think all the grooved BBC rocker balls from GM were PM just because of the grooves would be expensive to do in heat treated steel

[Jerry G.]

Re: powdered rocker ball broke

The plot thickens. i checked with several supplier, crane , lunati, isky etc. i find that they are all purchasing the rocker balls from Elgin. They are all powdered. i confirmed with elgin engineering that they are indeed powdered metal. does anyone know of a supplier that is not powdered metal?
has anyone used the sealed power rocker design ZR 826 ? Its design is more like the Ford rocker with a barrel shaped shoe that goes in the rocker rather than a ball. i'm getting a little desperate here. Broken ball floating around an engine makes for a VERY unhappy race day.

[Duke W.]

Re: powdered rocker ball broke

Does anyone know when SB rocker balls were changed from steel to powdered metal?

I don't think PM technology for low cost mass production even existed until the the eighties.

Maybe Jerry would be better off getting an old set off a junkyard motor that was built before PM technology took over.

Another issue could be compatibility of the specific ball and rocker. I recall that Chevrolet recommended using "run-in" matched sets for racing engines. In fact, they said if an exhaust ball burned, move the inlet over to the exhaust side and put the new set on the inlet side. I assume the exhaust side has more tendency to burn because it runs hotter, which can break down the oil film.

I agree that they worked okay in Trans-Am racing, but I think they had some teething problems and finally learned that using well run in matched sets of rockers/balls was required to make them live.

Given that Jerry's problem was a broken, not a burned rocker ball, it indicates excess stress rather than an oiling problem, which could be a result of mismatched parts or possibly some kind of interference.

Duke

[Clem Z.]

Re: powdered rocker ball broke

The plot thickens. i checked with several supplier, crane , lunati, isky etc. i find that they are all purchasing the rocker balls from Elgin. They are all powdered. i confirmed with elgin engineering that they are indeed powdered metal. does anyone know of a supplier that is not powdered metal?
has anyone used the sealed power rocker design ZR 826 ? Its design is more like the Ford rocker with a barrel shaped shoe that goes in the rocker rather than a ball. i'm getting a little desperate here. Broken ball floating around an engine makes for a VERY unhappy race day.

i posted above go find some old chevy engines and use those rocker balls

[Michael H.]

Re: powdered rocker ball broke

Given that Jerry's problem was a broken, not a burned rocker ball, it indicates excess stress rather than an oiling problem, which could be a result of mismatched parts or possibly some kind of interference.

Duke

I have to wonder if a bit of valve float would cause this problem? PM may be wear resistant but also more brittle than the old steel rocker balls.

We used the latest rocker arms that engineering released in mid/late 1968 and never had any issues with the arms or balls. The last three of the part number were 290, if I remember correctly.

In 1970, we used the Trans-Am engine, complete with GM crossram and stamped steel rocker arms for drag racing. I KNOW I floated the valves near the end of every run and never broke any valve train components.

I agree, a good "run in" set of original "O" rocker arms and balls would be my choice. Just watch out for valve float. That's what breaks these components.

[Duke W.]

Re: powdered rocker ball broke

Good analysis! If the valve gets tossed off the top of the lobe and then comes crashing down on the closing flank, it will put a hell of a compressive shock load on the ball, which could break it, but I think real steel would be much more tolerant.

Has anyone ever seen this type of failure on a real steel rocker ball?

Duke

[Joe L.]

Re: powdered rocker ball broke

Does anyone know when SB rocker balls were changed from steel to powdered metal?

I don't think PM technology for low cost mass production even existed until the the eighties.

Maybe Jerry would be better off getting an old set off a junkyard motor that was built before PM technology took over.

Another issue could be compatibility of the specific ball and rocker. I recall that Chevrolet recommended using "run-in" matched sets for racing engines. In fact, they said if an exhaust ball burned, move the inlet over to the exhaust side and put the new set on the inlet side. I assume the exhaust side has more tendency to burn because it runs hotter, which can break down the oil film.

I agree that they worked okay in Trans-Am racing, but I think they had some teething problems and finally learned that using well run in matched sets of rockers/balls was required to make them live.

Given that Jerry's problem was a broken, not a burned rocker ball, it indicates excess stress rather than an oiling problem, which could be a result of mismatched parts or possibly some kind of interference.

Duke

Duke------


I'm not sure that rocker balls were EVER forged steel. I have some very old NOS small block rocker balls for 1955-56 applications that were discontinued and superceded in 1957 and they appear to be powder metal, although I can't be 100% sure. It's not so easy to differentiate forged steel from powder metal.

Powder metal for at least one Chevrolet V-8 application has been around for a LONG time. The first part that I know of to be powder metal? Crankshaft timing sprockets. I think these were powder metal all the way back to 1955. However, I'm sure that 1967+ were powder metal.

[Domenic T.]

Re: powdered rocker ball broke

I think Clem has the answer using old rocker balls.
Never saw a failure if they had oil. They are a dime a dozen.

DOM

[Joe L.]

Re: powdered rocker ball broke

I have to wonder if a bit of valve float would cause this problem? PM may be wear resistant but also more brittle than the old steel rocker balls.

We used the latest rocker arms that engineering released in mid/late 1968 and never had any issues with the arms or balls. The last three of the part number were 290, if I remember correctly.

In 1970, we used the Trans-Am engine, complete with GM crossram and stamped steel rocker arms for drag racing. I KNOW I floated the valves near the end of every run and never broke any valve train components.

I agree, a good "run in" set of original "O" rocker arms and balls would be my choice. Just watch out for valve float. That's what breaks these components.

Michael------


Yes, the part number was 3974290. This was the last small block conventional rocker arm. It was released in late 1969 and survived until July, 1989 when it was replaced by the GUIDED-style rocker arm, GM #10089648.

I have a large number of NOS examples of the 3974290 rocker arm. By the packaging I would say they date from the mid-80's. They have powder metal rocker balls although I do not know, at the moment, if the rocker balls supplied with these arms were always powder metal.

[Clem Z.]

Re: powdered rocker ball broke

Good analysis! If the valve gets tossed off the top of the lobe and then comes crashing down on the closing flank, it will put a hell of a compressive shock load on the ball, which could break it, but I think real steel would be much more tolerant.

Has anyone ever seen this type of failure on a real steel rocker ball?

Duke

i think that ball was just defected. i never saw that before. get all the rest cracked checked or xrayed and i think you will be alright. i think that all BBC rocker balls were PM or they would not have had those oil grooves in them as each grove would have had to been machined one at a time. anyone have a old original BB rocker ball from the 60s ??

[Jerry G.]

Re: powdered rocker ball broke

if anyone has old rocker balls that are not powdered metal and would like to sell some. i could use a couple of sets. just the balls.

[Clem Z.]

Re: powdered rocker ball broke

i would order in (1) ZR1118 as it says it has a roller fulcrum and it is 1.5 ratio and 3/8" stud and see if it would work. those other ZR826 looks like it has a PM fulcrum.

[Tracy C.]

Re: powdered rocker ball broke

Jerry,

I have a used set of stamped rockers, balls and nuts off a passenger car 327. Pm or email your snail mail address and I'll ship them to you free..

tc

crisler@pixius.net

[Joe C.]

Re: powdered rocker ball broke

]I was dynoing a new camshaft in my road race motor small block 64 FI and as i was checking the stamped rocker lash i noticed a ball was broken cleanly in half. This surprised me, Clem explained that the ball was powdered metal not a forging. Anyone ever seen this before? I think i would rather have forged rocker balls.
What do you experts think about powdered vs forged or cast/ who is a reputable supplier for a race application? jerry

Do your race rules allow for higher lift cam? If so, then what are the cam specs? Did any spring experience coil bind?

[Philip C.]

Re: powdered rocker ball broke

The 67-69 SCCA Trans Am Camaro's had to use stamped steel rocker arms and they survived at high RPM for hours.

True Mike but they were not running high valve spring rates like today, we had to run rev kits to kept the roller lifters on the cam. Phil 8063