more bent push rods

Grumpy · May 27, 2016

Just swapped a stock 350 four bolt crate motor into my sons '73 K-20. At about 200 miles it had a slight lifter tick, so pulled the Valve Cover(VC) to adjust the rocker. Found the #6 exhaust rocker completely off the valve & the push rod(PR) bent. Opposite side #5 had a bent PR but the rocker was still on the valve.
Thought maybe a bad lifter, so pulled the manifold & replaced the lifter & PRs(orig lifter was fine, but replaced it anyway). Checked/Set the cold lash on all 8 cyl. Cranking the motor over to start I found after a very short time that the #6 exhaust rocker is out of alignment & walking its way off the valve again. Not sure yet if the PR is bent, but first glance it doesn't seem to be centered in the hole like the others, so I'm guessing it's in the process of bending. It was getting dark & starting to rain & I was frustrated, so I didn't check #5 PR to see if it's bending again. Rocker studs look perfectly aligned, Rocker arms look fine.
I'm searching for probable causes & not coming up with much.
Any ideas?
Thanks.
B-

you may not want to hear this or believe it but,it takes hundreds of lbs of force to bend a push rod
if your bending push rods, theres a REASON, and youll need to logically test and locate the source of the problem
SOMETHINGS BINDING, OR INCORRECTLY TIMED, OR BADLY ADJUSTED
and you darn sure better locate the source of the problem before you damage the lifters and cam,its amazing how many people don,t bother to carefully check valve train clearances and geometry ,check for parts , like rocker to rocker stud or push rods binding, or valve springs binding
ESPECIALLY if you changed rockers or the cam your using!
you may have coil bind, or improper valve train geometry or clearances, or valve train component s don,t match correctly, OR THE CAMS TIMING GEARS NOT INDEXED CORRECTLY
OBVIOUSLY YOULL WANT THE CORRECT VALVE SPRINGS
you need EITHER PUSH ROD GUIDE PLATES
BELOW NOTICE SCREW IN ROCKER STUDS

re-read these threads,
linked here and obviously youll need to verify all the valve train clearances and valve spring load rates,
if the valve train geometry check tool and the narrow sweep marks indicating wear on the valve tip indicates the geometry is correct,
your good to go on push rod length

http://garage.grumpysperformance.co...rect-custom-length-pushrods.14241/#post-72366

http://garage.grumpysperformance.co...sh-rod-length-checker-tools.13735/#post-70650

http://garage.grumpysperformance.co...-rockers-and-the-pushrods-rub.198/#post-46839

GrumpyThe Grumpy Grease MonkeyStaff Member

https://www.crower.com/clearance.html?cat=1541

you might want to buy a few of these
while they are on sale at a reduced price

heres a bit of useful related push rod length info (POSTED HERE) youll want to select the correct set or SETS for your shop

Big Block Chevy, Standard Length Big Block Intake 3/8" / .080" 8.275"
295-7941-8 Big Block Chevy, Standard Length Big Block Exhaust 3/8" / .080" 9.250"
295-7969-8 Big Block Chevy, Standard Big Block +.100" Long Intake 3/8" / .080" 8.375"
295-7979-8 Big Block Chevy, Standard Big Block +.100" Long Exhaust 3/8" / .080" 9.350"
295-7951-8 Big Block Chevy, Standard Length Big Block Tall Deck Intake 3/8" / .080" 8.675"
295-7961-8 Big Block Chevy, Standard Length Big Block Tall Deck Exhaust 3/8" / .080" 9.650"
295-7800 V8 396-454 Retro Fit Pushrod Set, Intake & Exhaust, 1965-Present
3/8" / .080"
3/8" / .080" 7.725 Int.
8.675 Exh
295-7913-16 Small Block Chevy, Standard Length Small Block Chevy 3/8" / .080" 7.800"
295-7984-16 Small Block Chevy, +.100" Long 3/8" / .080" 7.900"
295-7934-16 Big Block Ford, Standard Length Ford `72-'78 429-460 3/8" / .080" 8.550"
295-7951-16 Big Block Ford, Standard Length Ford `69-'71 429-460 3/8" / .080" 8.675"
295-7582-16 Oldsmobile, Std Length 455 5/16" 9.550"

Reduced
Part Number: 70463-2
Checking Pushrods
Checking Pushrods 7.975 +-.250 (Pair)
Learn More
Regular Price: $28.13

Your Price: $13.99
Reduced
Part Number: 70461-2
Checking Pushrods
Checking Pushrods 7.150 +-.250 (Pair)
Learn More
Regular Price: $28.13

Your Price: $13.99
Reduced
Part Number: 70465T
Checking Pushrods
Checking Pushrod Kit (1) 8.150 +-.250 (1) 9.150 +-.250
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Regular Price: $28.13

Your Price: $13.99
push rod too short
WIDE SWEEP ON VALVE TIP FROM ROCKER ADDS ADDITIONAL,
SIDE LOAD WEAR

push rod length correct
AS CLOSE TO CENTER AS POSIABLE BUT BEING CENTERED IS LESS IMPORTANT THAN MINIMAL SWEEP ON THE VALVE TIP< INDICATING MINIMAL SIDE LOADING
be aware that you need to measure BOTH the intake and exhaust push rod length as they can be different and ON the older BBC are designed to be totally different length, theres also 3/8" and 7/16" diameter BBC push rods and STANDARD AND TALL DECK SETS, and it should be obvious that the guide plates need to match the push rod diameter, being used, in each application as well as the correct length selected.
wall thicknesses vary from about .060 up through about .140 on most designs materials vary also, and larger diameters tend to be significantly more rigid resisting deflection under higher spring load rates, and inertial loads due to more radical roller cam lobe designs and higher rpms.

http://www.cpgnation.com/forum/threads/ ... etry.4346/

http://www.cpgnation.com/forum/threads/ ... tech.2408/

http://www.hotrod.com/how-to/engine/hrd ... vesprings/

http://www.summitracing.com/search/...d-length-checkers?autoview=SKU&ibanner=SREPD5
Proform Pushrod Length Checkers 66789 SBC 3/8" rocker studs

Proform Pushrod Length Checkers 66790 SBC 7/16" rocker studs

Proform Pushrod Length Checkers 66806 BBC 7/16" rocker studs
OR SELF ALIGNING ROCKERS (BELOW)
USED WITH PRESS IN ROCKER STUDS

used with press in rocker studs

yes they DO MAKE ROLLER ROCKERS IN BOTH STANDARD AND SELF ALIGNING VERSIONS

check all valve train geometry and clearance on any engine you assemble or modify the valve train on.

if your heads have push rod guide plates you are not supposed to use self aligning rockers as yes they will frequently bind the push rods up and keep them from spinning, if you have guide plates you want the NON-self aligning rockers
as I've pointed out dozens of times a day spent reading links will save you a week of work and a wheelbarrow full of wasted cash.

http://garage.grumpysperformance.co...s-in-vs-threaded-rocker-studs.2746/#post-7475

http://garage.grumpysperformance.com/index.php?threads/valve-train-clearances-and-problems.528/

http://garage.grumpysperformance.co...-in-vs-threaded-rocker-studs.2746/#post-43539

http://garage.grumpysperformance.com/index.php?threads/push-rods-rub.13031/#post-67779

http://garage.grumpysperformance.co...-rockers-and-the-pushrods-rub.198/#post-56571

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.co...-pushrods-and-check-info-you-might-need.5931/

http://garage.grumpysperformance.com/index.php?threads/stock-gm-push-rod-length.3844/

http://garage.grumpysperformance.co...ve-spring-iinstalled-height.12790/#post-66037

http://garage.grumpysperformance.com/index.php?threads/more-bent-push-rods.12401/#post-61890

http://garage.grumpysperformance.com/index.php?threads/rocker-push-rod-wear-issues.9815/#post-54088
http://www.competitionproducts.com/1500-1585-OD-Valve-Springs/products/2631/1/0

https://www.summitracing.com/search/part-type/valve-springs

https://www.iskycams.com/cart/valve-springs-c-99.html

http://www.cranecams.com/userfiles/file/334-343.pdf

https://www.racingsprings.com/Valve-Spring/Store/13

http://www.lunatipower.com/Category.aspx?id=23

http://www.pspring.com/products/engine-valve-springs/

http://www.competitionproducts.com/Valve-Springs/departments/49/

http://psisprings.com/products/

http://www.compcams.com/Products/CC-'Valve Springs By Usage'-0.aspx

http://www.racingsprings.com/Beehive-Valve-Springs

https://www.supertechperformance.com/valve-springs-p109

http://www.cvproducts.com/index.php/psi-springs/

REMEMBER TO CAREFULLY CHECK THE PUSH ROD TOO CYLINDER HEAD GUIDE SLOT AND CYLINDER HEAD CASTING CLEARANCES,IF THE PUSH ROD BINDS IT MAY CAUSE A LOSS OF OIL FLOW THROUGH THE PUSH ROD, FROM LIFTER TOO ROCKER OR THE LIFTER TO WEAR RAPIDLY
checking all valve train clearance issues in mandatory

almost every mechanics tool box needs a few basic measuring tools and supplies

https://www.amazon.com/Claytoon-Set...d=1466872286&sr=8-17&keywords=plastilina+clay

http://www.utrechtart.com/Plastalin...currency=USD&gclid=CN3G75zOw80CFQgaaQodKbgFjA
LINKS TO HELP you locate the issue
yeah I know you don,t want to read links
but it will take less time and effort ,
AND ITS CHEAPER than replacing more broken parts

more bent push rods

Grumpy

The Grumpy Grease Monkey mechanical engineer.