Last weekend I went to Orlando to race.
After 4 time trials(one of which was a PB of 10.83@124) I heard a chirping/squeaking sound that rose and fell with RPM...so I put it on the trailer. Sounded like it was coming from the #3 or #5 cylinder.
This is a new build(4 months old-25ish passes)
Finally got to dig into the engine and here is what I found:
1-Cut filter open—-Found some silver flakes
2-Removed rockers found gouges from the spring/retainer on 3 in a row. (#5 Int/Ex, #7 Ex.)
3-Held straight edge across rocker pedestals and believe those 3 are bent/crooked making the rockers swing closer to spring. I held the straight edge to them as I unscrewed the pedestal and saw the gap narrow and widen. (Leading me to believe the pedestal is bent vs. hole is crooked)
So...what causes a pedestal to bend? I made 26 passes and racked up 50-70 street miles since rebuild before I heard the squeak/chirping sound that caused me to rip it apart.(heads were not rebuilt when engine was rebuilt)
Any other things to check? Reasons to dig deeper? Assessments of problem?
Could this damage have made such an audible sound?
Should I lengthen my push rods to get the rocker away from the spring more?
This is a hydraulic roller engine.
A lot of what ifs….but looking at the pattern on the tip of the one valve affected, it looks sporadic as if the lifter may be pumping up and changing the geometry. I cant determine in the photos but any evidence of the rocker and polly-lock contact within the fulcrum slot? Does it ever idle rough immediately after some elevated rpm usage?
It sounds like you have 3 bent rocker studs. Since the other 13 are fine, no need to replace pushrods.
The witness marks left on the tips of those studs by your poly locks are significant, making me think those studs are not as hard as they should be.
Buy a set of ARP rocker studs. Mine have been adjusted many times, and they are hard enough that I can still see the "ARP" stamped on the tips of them.
Dan "Jim" Moore
Much too young to feel this damn old!!
Are you using a rocker stud girdle?
Jerry, No sign of any wear from the poly locks..and I have not noticed any difference in idle after a blast.
I went back and checked all the valve tips and it definitely has a different wear pattern. All of them have a spiral shape with a small center. The valve in question(#5 INT.) has a much bigger center area...more like a ring.
Get good quality studs and a good girdle for the setup from a good name brand that is built for your heads. Reassemble and check and triple check geometry and keep a periodic eye on things.
Configuration: 3350#, 582 C.I.,
60 - 1.24
1/8 - 5.53@ 126MPH
1/4 - 8.73@ 159MPH
3700#+210lb driver, FULL interior, through mufflers, 10.5 tire.
60'-1.333 (IN 4000ft DA! Joisy Math excluded; 1.25sec using JOISY MATH.)
1/4 - 9.60@144MPH
Jim...I looked at all the stud tips and took a poly lock apart and you’re right. Those circles are witness marks from the lock. I thought it was just part of the design.
So...how do 3 studs/pedestals bend...all in a row?
Can they bend all at one time?
Does any one think thos marks on the rockers caused the sound?
The chirping/squeaking sound appeared on start up in the staging lanes after 4 runs)
My previous run I actually short shifted...so it was definitely not over revved.
MarkMark...No stud girdle.
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Pedestal? WTF is a pedestal? Is it some kind of adapter, Olds specific? The studs don't screw into the head? If it bent the "pedestal" adapter or whatever it is, that would mean it needs a stud girdle probably. Post good a picture of it. Stand back a little taking the pic.This message has been edited. Last edited by: Mike Rietow,
Sorry...Stock Olds rockers are “pedestal mount”...so I inevitably still call them that...
I mean studs.
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If you're speaking of the head, it didn't bend the head or the stud hole, it bent the stud.
The squeaking could be debris anywhere squeaking. Looks to me like possibly the three studs were bent on assembly or were bent for some time. Was the head dropped? The rocker arm won't sqeak, it'll just clearance itself.
A pedestal is: 1. A support or foundation. The raised portion of the head casting which is subsequently machined flat then drilled and tapped is indeed a pedestal. FYI, "Occasionally paired trunnion rockers will bolt directly to stock pedestals, these kits generally cost less." Now you know what a pedestal is, wonder no more.
Illegitimi non carborundum
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Thanks, The mention of bending the "pedestal" while looking at a close up of a screw in stud had me picturing some kind of Olds specific screw in stud adapter. How do you bend the head "pedestal"? Ya don't, the screw in stud is bent.
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My guess would be.....
The rocker arms hitting on one side of the retainer is tilting the rocker arm (and roller) so it's riding on the outside edge of the lash cap and is actually spinning the cap on the valve tip and making the odd spiral pattern.
Any bend in the stud would probably just make this worse.
The squeaking you're hearing may be the extra load being put on one side of the trunnion bearing(s) getting hurt....I would assume if you take care of the gometry issues all noise will cease.
Sense it's only a few rocker arms being damaged I would look hard at those rocker arm studs and correct as needed.
F J B
I believe you are 100% correct on the first part. I held a straight edge across the good STUDS and unscrewed a few of the studs in question...you could see the stud lifting and letting down the straight edge with every revolution. Definitely bent STUDS.
Not sure about the noise yet...
Silver flakes in the filter? Are they aluminum from the rockers or something else? Did you try a magnet on them?
Recommend looking real hard at lifters/cam while you have it apart.
"It is usually futile to try to talk facts and analysis to people who are enjoying a sense of moral superiority in their ignorance." -Thomas Sowell
Every time I have ever heard what the op describes, it was a roller lifter going bad.
72 Nova "Hooptie"
Are they 3/8 or 7/16 studs. I bent 3/8 studs a long time ago with a mild hydraulic roller cam. Got a set of lower grade ARP studs, and then snapped one! Didn't know they had different grades back then, early 90's. Got a GOOD set of ARP studs and never had an issue after that, and never ran a stud girdle. Was a sub 7000 rpm engine.
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