Big block pushrod guide plates

Posted on Chevytalk as well...

OK...more on the 1996 Vortec 7.4 (GEN VI) - stock setup is 5/16" pushrods with nonadjustable rockers, uses guide plates.

Got a Comp Cams kit that is supposed to be a drop-in replacement to convert to adjustable. Roller tip rockers, studs, pushrods, etc.

The Comp pushrods are 3/8". OK, that's great - love the thicker pushrods. But I don't have guideplates for them, and need to button this truck back up TONIGHT.

Ideas? Safe to "clearance" the guide plates a little so the 3/8" pushrods fit? There seems to be enough meat on the plates, but I'm far from an expert...which is why I'm asking here. :)

Richard
 

grumpyvette

Administrator
Staff member
if the push-rods don,t actually touch the edge of the guide plate slot at any time in the 720 degree engine rotation cycle, and the rocker stays centered on the valve stem, you can use the guide plates, but in an ideal world the roller rocker tips are centered on the valve stems and the push rods are centered in the guide slots. if you don,t like the adjustable rockers you can cut and re-tig weld the standard guides, or tig weld the screws in the adjustable guide plates if your concerned with them moving, Id suggest using a number stamp, with the related cylinder to identify the correct installed location for each guide

man-42133_w.jpg

Proper push rod length is absolutely critical for peak performance—minimizing bent or broken valve stems, guide wear, and energy-wasting valve side-loading friction.
With the lifter located on the round base circle, position the Push Rod length Checker (make sure you have the Checker with the proper diameter hole) over the stud. Ideally the Checker should contact the top of the push rod and the valve tip evenly at the same moment, should the Checker contact the push rod first, measure the gap between the front of the checker and the valve tip, and purchase a shorter push rod of the correct length. Should the Checker contact the valve tip first, measure the gap between the back of the Checker and the top of the push rod, and purchase a longer push rod
prctool.png

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

viewtopic.php?f=52&t=181
as a temporary measure to get you rolling you can clearance the existing guide plates, but its very unlikely to allow exactly precise pushrod and rocker alignment on the valve stems.
http://www.racingsprings.com/1200_Series/sku/5 (and yes having a machine shop clearance the heads and do a mild port and bowl clean up to be sure the works done and clearanced correctly when swapping to the adjustable rocker arm and better valve springs is a really good idea as is a 3 angle valve job and new valve seals and having the valve guide clearance checked and then verify rocker geometry.
ROLLER rockers cost more but reduce friction and are usually good for a 20-25 hp gain on a big block
ValveSpringClearance01.jpg

gm_cylinder_heads.jpg

head_comp_cam_roller.jpg

heads+dart_pushrods.jpg

powerhouse_tools.jpg

ILL-VALVETRAIN-1.gif
[/img]
chevy+rocker_sweep.jpg


read thru the links it should help
In forced to agree with anyone who thinks this is rather obviously not a wear issue but points out that its bound to be an interference or geometry issue, it takes hundreds of pounds of force to bust push-rods


viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=4596&p=12263&hilit=guide+adjustable#p12263

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

viewtopic.php?f=52&t=1005&p=15534&hilit=rocker+geometry#p15534

viewtopic.php?f=44&t=4712&p=12798&hilit=rocker+geometry#p12798

viewtopic.php?f=52&t=196

http://www.airflowresearch.com/bbc_install.php

what you really should do is order these

Dart 27001230-4 - Dart Pushrod Guideplates

301-27001230-4.jpg



viewtopic.php?f=44&t=2839&p=7344&hilit=adjustable+guide#p7344

viewtopic.php?f=52&t=155

adjustablepush.jpg

adjustablepush1.jpg

adjustablepush2.jpg
 
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grumpyvette

Administrator
Staff member
heres a really interesting series of pictures taken when a guy was checking the correct push rod length and rocker geometry on a big block chevy, he noticed the dial indicator readings were not consistent, the cause was traced to the push rod guide plates contacting the push rod and binding the push rod making the tip move across the rocker push rod pivot cup. if the engine was run like that with the push rod binding in the guide plate parts failure was certain to occur in a reasonably short time

Rocker1closed.jpg


Rocker2mid-lift2.jpg


Rocker3fulllift.jpg


Rocker5.jpg


notice the adjustable length checking push rod used below and the push rod binding in the guide plates

Rocker4.jpg

I can,t even begin to tell you how many times I see guys slap a new cam in an engine and not carefully verify all the rocker geometry and clearances, and it sure does not take a great deal of valve train binding to cause serious problems

heres a bit of useful related push rod length info
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"
 
Last edited by a moderator:

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
pushrodr1.jpg

prpr1.jpg

prpr2.jpg


you should very carefully inspect any used rockers or push rods before you use the two, as any previous wear areas will in most cases cause rapid wear on the new component mated to the worn surface, and obviously the rockers must be clearanced correctly and have obvious oil flow from the push rods

its not horsepower, its the stress on the valve train, that makes a rocker stud girdle and its increased rigidity useful,
and thats more closely related to average stress levels, RPM and VALVE SPRING LOAD RATES
any time your occasionally exceeding 6000rpm or getting close too 330 lbs of open valve load rate Id strongly suggest screw in rocker studs
any time your intentionally exceeding 6000rpm and exceeding 350 lbs of open valve spring rate a rocker stud girdle might be a good idea.
and if your regularly exceeding 6500rpm and 400 lbs of open valve spring load rate its use is going to become almost mandatory
http://www.summitracing.com/parts/pro-66950

http://www.summitracing.com/parts/sum-141010

pushrodr2.jpg

HERES A SBC with a push rod checker installed showing an obviously too long for the application push rod.
prctool.png

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


pushrodr3.jpg

since the early mark IV BIG BLOCK engines use two different length push rods (INTAKE/EXHAUST) the checker is designed to be reversible, and marked to indicate which position it needs to be used with, to indicate the correct length push rods
notice in the pictures directly above and below it appears the push rods are a bit too long

pushrodr4.jpg

pushrodr5.jpg

pushrodr6.jpg

notice in the two pictures above the pushrods are the correct length as the checker sits on both the valve tip and push rod tip
pushrodr7.jpg

pushrodr8.jpg

heres a bit of useful related push rod length info
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"
obviously the push rods must be long enough to clear the push rod guide plates rockers through the full arc of movement and not bind on the springs retainers or rocker stud at full lift or while the lifters seated
pushrodr9.jpg

pushrodr10.jpg

push rods should also not rub on the guide plates at any point in the arc as it moves the valve from seated to full lift and back too seated
pushrodr12.jpg

pushrodr13.jpg

pushrodr14.jpg

pushrodr15.jpg

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

http://garage.grumpysperformance.com/index.php?threads/rocker-push-rod-wear-issues.9815/#post-54232
rpo1x.JPG

some roller rocker too retainer combo clearance issues cause problems easily solved with beehive springs and smaller retainer diameters

beehivesprcl.jpg

retain6.jpg

0607phr_32_z+camshaft_basics+beehive_valve_springs.jpg

0607phr_31_z+camshaft_basics+valve_springs.jpg

0607phr_36_z+camshaft_basics+spring_surge.jpg

springyu1.jpg

springyu2.jpg

springyu3.jpg

springyu4.jpg

springyu5.jpg

retain6.jpg

the reduced diameter of beehive valve springs usually eliminates the rocker too retainer clearance issue
011-bbc-big-block-chevy-nitrous-comp-cams-hydraulic-roller.jpg

BEEHIVE SPRINGS GIVE A GOOD DEAL MORE ROCKER TO RETAINER CLEARANCE
http://www.kmotion.biz/instht.htm


http://garage.grumpysperformance.co...swap-in-1-6-1-ratio-rockers.10671/#post-46039
http://garage.grumpysperformance.com/index.php?threads/checking-piston-to-valve-clearances.399/
DON"T FORGET TO VERIFY SPRING BIND CLEARANCE AND PISTON TO VALVE CLEARANCE ETC>
drawsdf.jpg

RockerGeometry.jpg

CCA-7901-1_VV_xl.jpg

youll need these also
adjustablepush.jpg
adjustablepush1.jpg
adjustablepush2.jpg

in an ideal valve train geometry set-up the sweep mark on the valve tip will be very narrow and close to the valve center-line , but having the sweep mark narrow is more important than keeping it centered on the valve stem tip, the valve train does not like lateral or side ways loads on the valves and the wider sweep is an indicator of that issue, while a correctly set up valve train may have components that result in the valve tip sweep mark being slightly off the valve center-line this is not a major concern.
Its checking and verifying the valve train clearances and basic geometry that should be your major concern

tippattern.jpg

the clearances and rocker geometry (push rod length,spring bind rocker to rocker stud clearance, etc.) must be checked carefully prior to starting the engine

prctool.png

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

"THAT PLASTIC THING" is a PUSH ROD LENGTH CHECKER, THE PUSH ROD LENGTH CHECKING, AND ROCKER GEOMETRY TOOL, ARE ENGINE SPECIFIC, so you MUST USE ONE DESIGNED FOR THE SAME STUD DIAM. SPECIFICALLY FOR YOUR SPECIFIC ENGINE, to find the correct rocker geometry and push rod length. If you for example use one designed for 7/16" studs on a SBC and used it on a BBC with 7/16" rocker studs the result would not be close to correct, if the tool designed for one engine is used on the wrong engine, so be damn sure you use the correct tool.


look through this thread

http://garage.grumpysperformance.com/index.php?threads/two-loose-valve-locks.9687/#post-47884

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

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
" grumpy I've been looking at the adjustable push rod guide plates on my big block chevy, are they required? stock engines don,t have them?"

for several years even stock BBC engines ,(the markVI and mark V) as opposed to the (mark IV earlier BBC engines)
also don,t use adjustable rocker arms if your running a stock cam and valve train with stock O.E.M. heads you probably can get by without them,
swap to a higher lift cam and a longer duration and aftermarket heads and better valve strings and in my opinion,
you would be very foolish to build and use a performance BBC engine without adjustable push rod guide plates
what you really should do is order these
Dart 27001230-4 - Dart Pushrod Guideplates

301-27001230-4.jpg



viewtopic.php?f=44&t=2839&p=7344&hilit=adjustable+guide#p7344

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