busted rocker stud??



busted rocker stud??

Postby grumpyvette » November 12th, 2008, 3:56 pm

KEEP IN MIND, MANY PEOPLE THAT HAVE BROKEN ROCKER STUDS HAVE FAILED TO VERIFY THE PISTON TO VALVE, CLEARANCES, ROCKER STUD TO ROCKER SLOT CLEARANCES,AND SPRING BIND CLEARANCES, etc.
it takes hundreds of pounds of force to bust rocker studs and or bend push rods, if you have those issues STOP AND LOCATE the geometry or CLEARANCE ISSUES CAUSING THE PROBLEM
theres several manufacturers and models available , heres a basic 1.5:1 ratio SBC version.
http://www.summitracing.com/parts/lun-85025
Image
Image
Image

Image
Upgrading to roller rockers or at least long slot stamped rockers will more than likely help, if you find your breaking rocker studs but checking your rocker geometry and valve train clearance is mandatory, and youll need to verify both clearances and geometry thru the full 720 degree engine rotation,and problems frequently only become obvious if you check,or if ignored until you develop problems (that way it gets expensive real fast)

if you install a cam with more lift the stock rockers and valve clearance is frequently not adequate.

read these, don,t skip the sub links and youll find it useful

viewtopic.php?f=52&t=181
[/size]
any change in the valve train components used requires verifying valve train clearances and geometry and potentially you might require new push rods, or rocker studs, springs or retainers ETC.
its been my experience that roller TIP rockers are a TOTAL WASTE of money in most cases, 90% of the friction is in the rocker ball area on the rockers or rocker stud roller bearing on roller rockers NOT AT THE TIPS that BARELY move .040- .050 across the valve tip in most cases, meaning the roller is rarely moving as much distance as a thin paper clip wire is wide

Image
Image
Image

Image
Image
Image

it should be noted that if the rocker stud protrudes into the port it should be trimmed to the port roof as any threads sticking down into the runner disrupt flow and don,t supply extra support to the rocker stud,and stud threads should use loc-tite tread sealant

the rocker stud failure could be the result of many things
but lack of oil flow, that allows the rocker ball to pressure weld to the rocker and snap off the stud is certainly a common one, it could certainly be a defective stud,and that appears to be the case here as theres no indication of extra heat and the break appears to be a stress crack, or its very unlikely but, too much spring pressure,could contribute to the failure.
in some cases the pushrod was clogged, the hole in the pushrod didn,t align with the hole in the rocker or the lifter was defective and was not pumping oil, but in some cases its not paying attention when the valves are adjusted, and getting the rocker adjustment nut, too tight, because that limits the oil flow rates , up the pushrod, and the lifter preload is pushed too far, or clearance issues are certainly suspect


from the ARP web site

Recognizing Common Failures

There are six types of metallurgical failures that affect fasteners. Each type has unique identifying physical characteristics. The following examples are designed to be used like a spark plug reading chart to help analyze fastener failures.

While few of us have access to sophisticated analysis equipment, a standard Bausch and Lomb three lens magnifying glass will generally show 98% of what we want to see. Several of the photos below have been taken utilizing a Scanning Electron Microscope (SEM) and are presented to simply illustrate typical grain configurations after failure.


Image

. Cyclic fatigue failure originated by
hydrogen embrittlement.

Some of the high strength “quench and temper” steel alloys used in fastener manufacture are subject to “hydrogen embrittlement.” L-19, H-11, 300M, Aeromet 100 and other similar alloys popular in drag racing, are particularly susceptible and extreme care must be exercised in manufacture. The spot on the first photo is typical of the origin of this type of failure. The second is a SEM photo at 30X magnification.

more info

http://www.arp-bolts.com/Tech/TechWhy.html

Image

5. Cyclic fatigue cracks propagated
from a rust pit (stress corrosion)

Again, many of the high strength steel alloys are susceptible to stress corrosion. The photos illustrate such a failure. The first picture is a digital photo with an arrow pointing to the double origin of the fatigue cracks. The second photograph at 30X magnification shows a third arrow pointing to the juncture of the cracks propagating from the rust pits. L-19, H-11, 300M and Aeromet 100, are particularly susceptible to stress corrosion and must be kept well oiled and never exposed to moisture including sweat. Inconel 718, ARP 3.5 and Custom age 625+ are immune to both hydrogen embrittlement and stress corrosion.
IF Im changing just the cam and lifters do I need to recheck the pushrod length?
JUST WONDERING,IF YOU HAVE STOCK LENGTH PUSHRODS,YOU MILL THE HEADS,USE THIN METAL HEAD GASKETS,WOULDN'T THIS PUT THE ROCKER ARM CLOSER TO THE CAM?THEN WHY DO YOU NEED LONGER PUSHRODS WHEN YOU INSTALL A BIGGER CAM THAN STOCK?YOU WOULD THINK YOU WOULD NEED A SHORTER ONE SINCE THE LOBE IS TALLER THAN STOCK AN THE ROCKER ARM IS CLOSER TO THE CAM BECAUSE OF MILLING & THINNER HEADGASKETS.



while your correct! the answers not always that simple because the cam base circle dia. on the new cam is frequently a differant dia. than the stock cam and the lifter seat height varies also, it will require verifyiong the correct valve train geometry.
you want the rocker to exert it force as much as possiable on the valve centerline to reduce friction and valve guide wear
YOULL NEED TO CAREFULLY CHECK YOUR PARTICULAR ENGINE!
heres a simple way to get close to the correct length
BUY ONE OF THESE
Image
Image
http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3567&prmenbr=361

after making sure the valve springs are correctly installed you drop the checker in place on the rocker stud and install your adjustable pushrod
adjust the length to fit and measure the resulting length if its within twenty thousands of the stock length its fine for most applications, if its more than 30 thousands long or short get the closest length set available

<b>btw, if your one of the people that still does not own an adjustable push rod! you can easily make your own by cutting a stock pushrod in 1/2 (2 pieces), removeing 1 inch from the total length an then with about 2 " of a 4 inch section of 3/16 or 1/4" thread rod installed and (in one section epoxy it in place leaving about 2" sticking out thread two nuts onto the thread rod and slip on the other end of the cut pushrod,(no epoxy) use the two nuts to adjust to stock length and let the epoxy harded in the one section[/color] now you can easily measure and order custom push rods useing the pushrod checker and adjustable push rod as tools
AND YEAH IT ONLY WORKS WITH THE CYLINDER HEADS ON AND THE INTAKE REMOVED BECAUSE THE HOLE IN THE CYLINDER HEAD that GUIDEs THE PUSH ROD WON,T ALLOW THE NUTS ON THE ADJUSTABLE PUSHROD TO PASS THRU, UNLESS YOU PLACE THE CUT ABOUT 1" from the UPPER END OF THE ADJUSTABLE TEST PUSHROD BUT I prefer to place the adjusting nuts centered as I like to watch for all clearances with the intake manifold removed while manually checking as I turn the engine over by hand durring assembly, and at that point, while checking all the clearances, I use test springs which apply very little load on the push rod</b>
Image

http://www.jegs.com/cgi-bin/ncommerce3/ProductDisplay?prrfnbr=3272&prmenbr=361

HERES OTHER TOOLS YOU MIGHT NEED
Image

Image

Image

Image

SOMETHING TO READ
http://www.compcams.com/information/Products/Pushrods/
Image
CCA-7705 5.800 in. to 9.800 in. adjustment range, Master pushrod length checker 4 piece kit ... $78.69

here

http://www.circletrack.com/techarticles/ctrp_0611_rocker_arm_valvetrain_geometry/index.html

http://www.circletrack.com/techarticles/ctrp_0611_rocker_arm_valvetrain_geometry/roller_tip_rockers.html

http://www.compcams.com/Technical/FAQ/ValvetrainGeometry.asp

http://www.babcox.com/editorial/ar/eb50232.htm

viewtopic.php?f=52&t=181&hilit=rocker+studs

viewtopic.php?f=52&t=399

viewtopic.php?f=52&t=1376&p=3030&hilit=pushrod+length+checker#p3030

viewtopic.php?f=52&t=1005

viewtopic.php?f=52&t=4957

http://www.customspeedparts.de/content/en/technic/kipphebelgeometrie.php

http://www.hotrod.com/techarticles/camshaft_tips_definitions/index.html

http://www.eatonbalancing.com/blog/2007/12/10/rocker-arm-geometry/

http://www.fordmuscle.com/forums/engine ... tools.html
Image
Image
Image
Image
Image


viewtopic.php?f=52&t=399

viewtopic.php?f=52&t=528

viewtopic.php?f=52&t=7716

viewtopic.php?f=52&t=5902

viewtopic.php?f=52&t=4957

viewtopic.php?f=52&t=2661

viewtopic.php?f=52&t=2746
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: busted rocker stud??

Postby grumpyvette » November 15th, 2008, 4:15 pm

http://www.lonniesperformance.com/

posted this info
Here is an example of what high spring pressures can do.
This is the consequence of using high spring pressures on a new LS7 427 Z06.

Image


Image


Image

Obviously not a lot of people will be running solid rollers with 250deg .600+ lift cams & springs with over 200# seat pressure... but they can take their toll.

A rigid shaft mount system can spread the load over multiple mounting points, to help prevent this type of problem.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: busted rocker stud??

Postby grumpyvette » February 17th, 2010, 10:24 am

rockers and rocker studs, valve springs, rockers etc, rarely if ever break for no reason,valve train parts will last for years if properly clearanced and lubricated if the geometry and loads are within spec. theres almost always without exception, a clearance or geometry issue, thats the cause,it requires hundreds of lbs of force, to snap off a rocker stud, and thats almost always the result of a clearance issue like spring bind or rock slot to rocker stud clearance being too tight or the rocker/valve train geometry being wrong., just because some component rotates without binding up , does not mean its going to function at higher rpms and loads
if you have not verified all the clearance issues Id strongly suggest you look into that.


viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=1376

viewtopic.php?f=52&t=528

viewtopic.php?f=52&t=1005

viewtopic.php?f=52&t=399

http://www.maxchevy.com/tech/2007/ii_12-stud-1.html

IM always amazed at the guys that think swapping from 3/8" to 7/16" rocker studs is going to be a huge improvement,in valve train stability,now theres not the slightest doubt that an increase of about 18% in cross sectional area on the studs a significant increase in strength, and while that helps, its not the huge improvement many people think it is because its generally not the rocker studs that fail from flexing,unless they are defective, as most would have you believe, but because its the rocker geometry and rocker support not the stud diameter, that matters, more, you can,t expect a rocker stud with one end unsupported to have any where near the resistance to deflection that a rocker stud with BOTH ends supported will have.
if you support both ends of the rocker studs you easily increase the load bearing capacity to far more than the additional stud diameter increase, can ever do,having one end unsupported the stud acts a bit like a nail being pulled by a hammer, in that loads applied to the upper end tend to both bend the nail and pull on the lower end thats where the use of STUD GIRDLES comes into play.
simply supporting the rocker stud tips so that the forces acting on a single rocker stud are now opposed by the resistance to deflection of all 8 rocker studs
is a huge improvement



http://www.summitracing.com/parts/SUM-141010/?rtype=10
Image
http://www.summitracing.com/parts/CCA-4014/
Image

viewtopic.php?f=52&t=1769

HEY GRUMPYVETTE??
Fresh build on a 427,

I started it for the first time last friday, ran the oil pump with a drill for 15-20 minutes before the start. The lash was set correctly. Had plenty of oil running out all the pushrods. I used a bottle of Lucas breakin oil along with five quarts of 10-40. Broke the cam in for 25 minutes, then changed the oil. I took it to the muffler shop on Monday morning. They made headpipes, and connected the exhaust. I drove it to work, then home. Total running time is 60-90 minutes, including the breakin.

Everything seemed fine, but Oil was leaking out the rear of the valve covers and smoking on the manifold so I pulled them and was putting in new gaskets when I saw a flake of metal next to a valve spring, I removed that rocker and this is what I found. I pulled all the rockers, and some valve stems have chips out of the edges, but this is by far the worst one. The tip of the rocker looks just as bad.
Image
What happened here?
Is this something I could have caused, or is this a problem with the engine builder?


thats obviously not normal wear,issue and it takes a huge amount of force to pressure shear the valve tip,in that short time,

Id bet you you find its a CLEARANCE issue, that type of damage usually indicates valve train binding, if your binding the valve train,pressure are immense, and parts fail rapidly, the most common on big blocks is the rocker slot binding on the rocker stud or spring bind or retainer to valve guide issues ESPECIALLY if the cam has more than about a .530 lift and your still using stock valve springs and rockers
but check the piston to valve clearance, verify the installed spring height,(you could have to many valve seat shims) and if you adjusted the pre-load or lash on the valves COLD ID strongly suggest AFTER VERIFYING CLEARANCES that you adjust the valves AT IDLE

Image

read thru the links

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=282

viewtopic.php?f=52&t=1005&p=1818&hilit=+shims+spring#p1818
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida


Return to Cams, Heads and Valve Trains

Who is online

Users browsing this forum: No registered users and 4 guests

cron