? Rocker arm failure - twice??

[wheels4fun]

Looking for help! Recently had my '66 140 rebuilt. Blew out #1 intake rocker arm at 500 miles (see photos). Today at 600 miles blew out #3 intake rocker in exact same fashion. Appear to be overheated as both are somewhat gunmetal blue. #3 exhaust has not failed but appears blue. Others on R bank look OK.

A few other facts: New Clarks mated grooved ball repo rockers, new Clarks deep dimple lifters, reused pushrods (oil passages fully open), 270 cam, new PEP springs with 105# seating force (not 'bottoming out' at full lift), reworked heads (deep seats, milled to remove all but .010" of land, mag bronze valve guides, etc.). Brad Penn 30W break-in oil for 600 miles. Just put in Brad Penn 10W-30 today. No loud tappet noises. Not over-rev'ed.

I planned to drive the car to Knoxville next week but am now having serious doubts.

Has anyone seen or heard of anything like this before???

Many thanks.

[bbodie52]

Are the push rods inserted backward? There is a small hole in the side of each push rod that is there to spray oil on the rocker arm to lubricate it. If the push rod is inserted upside down, the side hole will be near the hydraulic lifter instead of the rocker, and the rocker arm may not be getting adequate lubrication!



You can see a hole in the side of the rocker arm, next to where the push rod seats. This hole permits oil sprayed from the side of the push rod to pass into the rocker pivot ball area, to lubricate the ball and rocker arm. If the push rod is inserted upside down, very little oil would get to the critical pivot area, causing the ball to run dry and not be lubricated. This would overheat the rocker arm and ball, causing the results you have seen. If the engine builder was unaware of the design in these push rods, he may have inserted the push rods without regard to the oil hole in the side. Some may be properly inserted, while others may not.

[wheels4fun]

I did check this and the pushrods were installed properly, side hole at rocker end.

I put on a used rocker/ball combo and ran the engine with 'holed' valve cover on. Saw no oil squirting through the rocker hole into the ball/stud area but couldn't see if there was flow from the push rod end of the rocker. So pulled cover off and ran engine. All push rods supplying oil and of course oil being flung from rockers. Not sure if it was enough oil because I've never done this before.

Pushrods do rotate when valve is closed, although takes some force, so I'm assuming sooner or later oil would squirt into the ball/stud area.

Other thoughts??

[bbodie52]

I was certain that improperly inserted push rods woud be the cause. The only other thing I could think of was the rocker balls installed upside down, or the valve adjustment WAY too tight! (see the link below).

viewtopic.php?f=84&t=7567&p=50833&hilit ... ker#p50833

[Jerry Whitt]

Try removing the oil pressure switch, and install a direct reading oil pressure gauge. Test at different engine speeds and give us a report

[wheels4fun]

Thanks for comments and ideas. Replies:
- Valves were all adjusted at zero lash then 1/2 turn. I checked this today and valve adjustment still seems fine.
- I have a new oil pressure gauge in the dash. When the oil is hot the pressure is about 15 psig at idle and 40 psig when driving.

Kent

[miniman82]

Poor quality parts? I know you said Clark's, but sometimes OEM is better.

[66vairguy]

Rocker arms occasionally break in the area you pictured - BUT the bluing indicates an overheat problem which is NOT normal.

This is just speculation - but did you lube the new rocker balls with a break-in lubricant during assembly before the first engine start? The head area remains relatively "dry" at start up until the lifters pump up and drive oil up the pushrods. This is why it's recommended to keep an engine between 1,500 and 2,000 RPM for 15 minutes when a newly rebuilt engine is first started. While Corvairs use a pressurized oil system - the valve train and piston wrist pins rely on "splash" oiling that is not very effective at idle RPM.

The 270 cam has a considerable amount of lift and yes special valve springs are required for clearance. These springs typically have a greater tension and put additional stress on valve train parts (one reason I avoid the high lift cams - but that's just me). Since your head gasket area was cut, and combined with the higher lift, you may have a geometry problem between the rocker tip and valve shaft. This could create extreme side loads on the rocker and valve stem.

Another issue is the rockers may be hitting the rocker stud shafts. Did you look for "sawing" marks on the rocker studs?

Just a few things to consider. Others may have more to add.

[flat6_musik]

Are these valve springs okay to work on a street motor? I tend to look at these stamped steel/rocker ball rockers as a "grocery getter" application. After you're sure that the push rods are good, unplugged and "spitting" while running, I might consider stepping up to some nice roller rockers. But this would only be after ensuring 100% that you've got good lubrication going on (which I'm a little skeptical of).

[66vairguy]

Never assume the pushrods are "spitting" oil. Myself, and others, have had new lifters that would collapse and pump little oil up the pushrod tube.

Also -- a lifter that is improperly adjusted will not pump oil correctly. After zero lash you need a least a quarter turn down of the rocker nut to make the lifter pump oil up the pushrod. The same goes if the lifter is "bottomed out" by turning the rocker nut down too far.

Finally --- the pushrods will spin with the lifter and if they don't the oil hole in the pushrod won't distribute the oil well. If just one pushrod does not spin then the others can compensate. If two or more close together don't spin you've got a problem. Many times geometry issues will cause the pushrods to bind in the guide plate slots --- YOU DID MAKE SURE THE GUIDE PLATES WERE INSTALLED WITH THE CORRECT FACE UP!!

[66CorsaConv]

What does the inside ( not shown ) part of the rocker arm look like? What does the pivot ball from that arm look like? Someone else noted blue color. If that is not heat treat then it got real hot. No assembly lube maybe?

From what is shown it may be brittle fracture. Can't tell from the one picture.

BTW I may be able to locate some retired Chevrolet engine guys I used to work with to show them. When I started we had stamped rocker arms, distributors, and carburetors

I'm getting old. .

[davemotohead]

Bet you got some Chinese Quality parts, With the repop china stuff you have a 50/50 chance of getting junk.

[66CorsaConv]

Dave he said he bought the parts from Clarks. I only know about what I have bought from them and I'm more than happy.

[davemotohead]

I know they came from Clarks, Just saying the Chinese quality is random, Sometimes you Win and some times you don't, no reflection on Clarks, like I said,china stuff is a 50/50 crap shoot.

[tiger13]

As everyone knows, I am new to Corvairs, and do not know the specs of the "270" cam, but if it is a high lift cam, could it be that those rockers, or "some" of those rockers, particularly the ones that have failed or the ones that are showing signs of failure, are not, what we would have used in other small block Chevy applications when we used a high lift cam, and needed a "long slot rocker" to prevent binding at the rocker stud? If the rocker binds on the stud, it would cause cracks to form, and then the rocker would fail like that picture shows. Again, I am not familiar with the characteristics of this particular camshaft but have seen similar results in Chevy V8's when the slot in the rocker was not long enough. And did the poster say they saw oil at the rocker?

[66vairguy]

I doubt the original poster will be back - he went to the "other" forum and got a huge number of replies and possibilities.

Bottom line ---- he says he has adequate rocker/spring clearance and the pushrods are installed correctly. Defective rockers might be an issue, but if they turned blue AFTER he installed them, then that would indicate a lubrication issue.

One fellow (Marco) brought up an issue often overlooked - lifter bore wear. An engine with good bearings and lifter bore clearances should be able to produce 30-35PSI oil pressure at idle even when hot. When someone says they only get 10-15PSI at idle on a rebuild I figure they have a worn block - lifter/cam bores.