In my experience, breaking rocker studs has always been caused by the rocker
stand not being securely fastned down to the head so that the stand moves,
bends the stud and eventually it fatigues and breaks.
Check to make certain that there is no contact betweent the end cylinder
head stud and nut and the end of the shaft! If there is the nut and the
stand stud will torque up and feel tight but the stands will not be tight
down against the head. Make sure that the bottom of the stands are all dead
flat and that all of the stands are the same hight. There are aftermarket
"competition" rocker stands out there that come form England that are good
in concept but very poorly made. The ones that I have seen all needed to be
remachined as the stands were all different hights and the bottoms were not
flat. We also found that the way the stands were made there was not
provision for the stand to actually "grip" the shaft where the shaft goes
through the stand. Only the locating bolt in the number 4 stand holds the
shaft from moving around.
We have always used the standard stands, though I prefer the cast steel
TR-2 stands as I believe that they are more ridged. We use thick, hardened
washers on top of the stand, grade 8 "tall " nuts and torque the m to 35 to
40 lbs. ft. of torque. We use the stock studs. We have not so far had a
failure in over 30 years of building race and competition engines. In some
full race engines with over .500 inch lift at the valves we use over 250 lbs
of spring pressure when the valves are full open. We have experienced shaft
failure and manufacture billet 4130 rocker shafts to prevent that. For sure
the culprit in rocker stand stud failure on a regulare basis is that the
stand is not properly secured or located to that the stud is subjected to
alternating bending loads instead of a steady "tension" load ,which is what
it si designed to withstand.
Regards, Greg Solow
----- Original Message -----
From: <SpiwakD@AOL.COM>
To: <fot@autox.team.net>
Sent: Wednesday, September 15, 1999 5:29 AM
Subject: (no subject)
> Help needed. My trusty TR3 broke two number four rocker studs at Watkins
Glen
> with no obvious cause. The studs were grade 8. Piston clearance was
checked.
> I had the same problem the week before at Lime Rock. Anyone have any
ideas?
>
> Dave
>
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