valve train geometry

[grumpyvette]

KEEP in mind the main idea here is to keep BOTH the rocker arm pushing strait down the center line of the valve to minimize friction and valve guide wear,and to keep the pushrod length at the correct dimension to minimize friction and match the intended angle of operation designed into the valve train, and to do that the basic geometry and clearances, and geometry in that valve train must be correct...you may need too use the correct adjustable guide plates when you find the push-rod alignment is in need of minor tweaking to get the clearance and geometry correct,
don,t forget as many guys do, that swapping to a higher ratio rocker changes the push-rod rocker geometry,and clearances, the heads and rockers used obviously effect the required clearance, but you'll usually want at least 60 thousands clearance on the push rods to slot measurements and you'll want to rotate the engine thru two complete revolutions while verifying that clearance, while watching the push-rod geometry as it changes as the rockers move thru their arcs and may require a different length push-rods.

Pushrod Too Long: Notice how the pattern is wide, and shifted to the exhaust side of the valve tip.

Pushrod Too Short: Notice how the pattern is wide, and shifted to the intake side of the valve tip.

Pushrod Length Correct: Notice how the pattern is narrow and is centered on the valve tip.

if your rocker geometry, does not appear to be correct ,start at the basics
http://www.summitracing.com/parts/PRO-66789/

http://www.summitracing.com/parts/TFS-9001/

verify your correct geometry first

http://www.thedirtforum.com/pushrodlengths.htm

http://www.compcams.com/catalog/278.html

http://www.carcraft.com/techarticles/11 ... index.html



heres useful links and info below

http://www.compcams.com/information/Products/Pushrods/

http://www.trendperform.com/

http://www.popularhotrodding.com/engine ... ables.html

http://www.mantonpushrods.com/

http://www.aa1car.com/library/2004/eb30431.htm

http://www.cranecams.com/?show=technicalhelp

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

http://www.compcams.com/Technical/FAQ/V ... ometry.asp

http://www.grapeaperacing.com/GrapeApeR ... etrain.pdf

YOULL NEED TO CAREFULLY CHECK YOUR PARTICULAR ENGINE!
heres a simple way to get close to the correct length
BUY ONE OF THESE

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), removing 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 hardened 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>

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

HERES OTHER TOOLS YOU MIGHT NEED

SOMETHING TO READ
http://www.compcams.com/information/Products/Pushrods/

CCA-7705 5.800 in. to 9.800 in. adjustment range, Master pushrod length checker 4 piece kit ... $78.69
http://store.summitracing.com/egnsearch ... &x=36&y=11

 

[grumpyvette]

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.

. 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

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

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>

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

HERES OTHER TOOLS YOU MIGHT NEED

SOMETHING TO READ
http://www.compcams.com/information/Products/Pushrods/

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.mid-lift.com/TECH/TECH-Installed-G1.htm

http://www.circletrack.com/techarti...m_valvetrain_geometry/roller_tip_rockers.html

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

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

http://www.chevyhiperformance.com/tech/ ... index.html

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

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/

 

[grumpyvette]

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.

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.