Rocker Studs

[miketsouth]

Anybody ever see rocker studs flex?
350 SBC
993 stock "hecho in mexico" heads with 3/8 pushin studs.
xe274 cam, less than .5 lift
1.5 rockers
nothing special
After a failure due to the wrong rockers (should have had long slot rockers and kilt the top of some valves) i replaced the heads on my engine, using new roller tip rockers. Stamped cheep rockers with roller tips.
I was setting the lash on my SBC hydraulic cam and was looking at the rocker studs.
I was terrified to see them wiggle as the rocker pushed the valve up and down (cranking speed only)
I checked what i know of the rocker/valve geometry, looked ok. Roller riding on or near the middle of the vavle head, no spring bind, and the slot in the rocker is not touching the rocker stud.
I pulled one of the new rockers to see where the ball was rubbing and it was only touching in a few places. I figgered that they needed to break in.
SO, i went ahead and started it. Figured it would breakin or breakup, but the worst i could do was throw a lifter out of the bore into the valley.
Ran fine. Warmed it up. Set the timing, winged it a couple of times, set the idle and shut it down.
Opened the vavle cover and saw about the same thing: Studs move around with the rocker....lash still good lift still good.
WTF?
Is it that i just never looked before. I was on the fifth cylinder before i even noticed it, but it still was suprising.
Do i need a cheep stud girdle? Engine should never see over 5100rpm.
mikeT

[1BIGJIM]

I had the same problem years ago with a SBC. Mine kept pulling out. My temporay solution was to put roll pins through the stud to keep it in place. I ended up tapping all the holes, put in ARP studs and the issue was solved simple as that. To do it over again I would not waste the time on the roll pins unless its one stud. My 2cents, hope it helps.

[miketsouth]

It does. The way it looks is that there are two failure modes
1. Studs pull out
2. Studs break
cured by just what you said (pull the existing studs, tap them and install new ones. It looks like this can be done on the engine, using the right studs.
My research shows that the spring pressure should not be able to pull out the stud, but still they may come out
My reasearch shows that every once in a while a stud will break.
Did your studs visibly move? That is what suprised me. I thought they would snap right off, but they didnt. No visible bind or valve interference or bent pushrods or nothing i can see
The new rockers are kind of rough, though. The balls dont move smoothly in the socket. I am supposing that they have to break in, with the evidence being in the wear pattern in the rocker and that you must keep the same ball with the rocker, like lifters and the cam
I believe i will get tall vavle covers, stud girdles and some screw in studs. Gonna need them, i think. Hope the lifter survives in the valley pan.
mikeT

[miketsouth]

I ran the camera at the rockers but it just didnt show the movement like i wanted it to.
SO..i mounted a 3.5" bolt on top of the rocker, using the exposed threads and a nut to tie it to the rocker stud.
As an index i used a piece of solder mounted to a valve cover stud and placed it near the top of the indicating bolt.
The space between the solder and the bolt is .018" or so
The video is running at 25% of regular speed
0.4meg
21sec
video
short vid of rocker stud exercising (http://mywebpages.comcast.net/mikejet/rockerstuds4.wmv)
You can see quite a bit of flex. What cant be seen is if the rocker is stopped near its most (valve) open position,, the stud relaxes back to its original position. When returning from this point to its most (valve) closed position it flexes the other way. This, to me, is friction produced by the rocker ball joint.
Maybe like teeth, if i ignore it it will go away.

[miketsouth]

ok, i finally taked to someone who actually looked at them while they cranked. Said a dial indicator might indicate as much as .005" play.
Ok, so i guess i will just keep a tow boat handy.
Hear that Donny?
mikeT