rocker arm geometry with a new cam



rocker arm geometry with a new cam

Postby grumpyvette » October 19th, 2008, 9:18 am

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.



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

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

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

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

http://www.pontiacstreetperformance.com ... ngeom.html

http://www.lunaticams.com/Tech/Valvetra ... metry.aspx




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 ... index.html

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

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

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

http://www.customspeedparts.de/content/ ... metrie.php

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

http://www.eatonbalancing.com/blog/2007 ... -geometry/
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: rocker arm geometry with a new cam

Postby grumpyvette » October 22nd, 2008, 9:15 am

anytime ANY parts are changed you must check the engines clearances, your builder should know this!, heres a few things that should always be checked on an engine build

clearances, and geometry in that valve train must be correct...

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

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

Image
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/
Image

Image
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




these come in different designs but youll want ones matching your application
http://www.summitracing.com/parts/PRO-66789/
http://www.summitracing.com/search/Part ... -Checkers/

Image

Image
http://www.summitracing.com/parts/CCA-7901-1/


what are your valve train clearances? is the rocker arm geometry correct!
has the cam to rod bolt clearance been checked?
piston to valve clearances
rocker slot to rocker stud clearances
retainer to valve guide clearances
what were the piston ring to slot clearances?
piston to head clearance?
did the distributor gear fit the cam gear precisely?
are you possitive the pistons were installed with the correct valve relief in the correct location?(eiieeiie) were the pistons installed with the correct side facing forward/
did the head gasket overlap the bore?
what torque values were used on all fasteners/ were they the correct length and type bolts?
were the valve to valve guide clearances checked?
was the cam drive checked for free rotation and drag/
cam to timing cover clearance?
cam journal to cam bearing clearances?

were the spark plug threads of a installed spark plug extending into the combustion chamber checked? ?
was the cam degreed in or just lined up useing factiory index marks?
was the cam lobes/LSA/LIFT CHECKED?



http://www.fordmuscle.com/fundamentals/pistontovalve/index.shtml

http://www.lindytools.com/

Image
Image
http://www.iskycams.com/category_template.php?sub_category_id=133

link #1

[url=
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

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 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 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/

CCA-7705 5.800 in. to 9.800 in. adjustment range, Master push-rod length checker 4 piece kit ... $78.69

here
be sure you check clearances carefully, a mistake can and will damage the engine, DON,T GUESS<KNOW WHAT THE CLEARANCES ARE, ESPECIALLY SPRING BIND,VALVE TO PISTON,ROCKER TO ROCKER STUD, and retainer to valve guide clearances I still use the strips of modeling clay about 1" square and .2" (two tenths thick) but one thing everyone forgot to mention so far is that you need to spray the piston and valve and clay strips with WD-40 to ensure the clay does not stick to any parts, otherwise the clay will tend to stick to the valve and piston allowing them to push the clay between them during the compression of its surface by the valve (exactly what its there for) and PULL ON THE SURFACE of the clay as the valve moves away during separation (because the clay tends to stick ever so slightly as the parts pull away from each other if you don,t)which tends to give a false slightly greater than correct clearance measurement
most people tend to tell me I'm wrong about that until they try it both ways :grin: yeah the difference is usually minor but five to 10 thousands difference is not rare if the parts are clean and dry versus sprayed with an oil mist Image first check to make sure that you are measuring correctly, many times the valve actual has more clearance in the fly-cut clearance notches,or only the very edge of the valves head and the edge of the notch are close and very minor cutting with a tool fitted in a valve guide will clear the problem and the valve has more clearance than measurements taken from the pistons upper surfaces, and that the head gasket thickness and valve train geometry are correct,
check if changing the cam retard/advance or installed position can be changed to increase the clearance to 0.100 minimum on both the intake and exhaust valves (MOST LIKELY TO WORK WITH THE LEAST PROBLEMS)
why is it that so many of you gentlemen are so reluctant to actually take the time to measure valve train clearance, spring load rates and valve train geometry and make every effort to avoid doing things correctly?
yes it takes some knowledge, some tools and some time, but in the long run its gives you some piece of mind knowing its been done correctly, and your far less likely to have catastrophic engine failures as a result.

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=2746

viewtopic.php?f=52&t=2661

add a thicker head gasket? ( BUT THAT TENDS TO RUIN QUENCH AND DOES NOT TEND TO BE A GREAT CHOICE ON MOST ENGINES)

look over the isky site they and MANY OTHER HOD ROD TOOL SUPPLY SHOPS SELL TOOLS THAT APPEAR TO BE EXTRA LONG STEM VALVES WITH CUTTERS ATTACHED TO FIX THAT PROBLEM
http://www.iskycams.com/pdfcatalog/PAGE17.pdf
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: rocker arm geometry with a new cam

Postby grumpyvette » October 23rd, 2008, 2:10 pm

HEY GRUMPY!
I've found that I have a collapsed lifter ( I'm almost positive) and as long as I'm in the engine I'm going to get rid of the flat tappet and go with a hyd. roller. The current one is 218/224 duration @ .50 with .462/.469 lift with 1.5 rockers. The one I'm looking at is 222/230 duration @ .50 with .518/.539 lift with 1.5 rockers. I'm pretty sure it will work with my computer. My concerns are---the valve springs I have are good to .575" lift and have 105 lbs seat pressure. The guy @ Crane cams said to just add .030" shims under the springs to get to 150 lbs seat pressure. With these shims, won't I be too close to completely compressing the springs with the increased lift? Also, how do I figure out the length of the new pushrods? (I'm not an engine guru :D ). Thanks in advance! Art.

the .030 shims reduce the valve lift clearance from .575 to .545 and add the necessary load to the valvetrain, NOTHING in the pushrod geometry changes, no new pushrods are needed, due to the shims alone if nothing else changes, naturally if you swap to a roller cam the increased lifter height of the roller lifter requres a shorter pushrod length
BTW if youve installed 1.6:1 ratio rockers and the pushrods rub...in the guide slots in the cylinder heads,
this is a common problem,easily solved...
YOU NEED A louis tool, YOU WANT ABOUT .060 CLEARANCE, IT MAKES THE JOB EASY
This tool was designed to simplify the modification needed when using 1.6 rocker arms on SB-Chevy heads. It allows you to use a hand drill with a 5/16'' bit to elongate the pushrod slot exactly in line with the existing slot, thus eliminating the need for guide plates.
Image
stock stamped rockers are cheap but the ratio is usually not precise and the slots for the rocker studs can bind at high lift plus they easily restrict 10-15 hp in friction losses.
Image
Image
roller tips are usually more precise ratio rockers but don,t look for any huge reduction in friction

Image
true roller rockers can frequently free up 15-20 hp in reduced friction.
http://www.popularhotrodding.com/engine ... ables.html

Image

http://www.compcams.com/Products/CC-%27 ... %27-0.aspx
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: rocker arm geometry with a new cam

Postby grumpyvette » October 23rd, 2008, 3:26 pm

Would .006" be enough room to spare in spring compression"

that depends on both how accurate the valve train measurements are and how they calculate the clearance,......normally when the valvesprings max lift height is listed or posted rated at a .575 lift,etc. theres a .050-.060 thousands extra clearance between the true spring stack height and the advertized max valve lift IE your advertized .575" max lift spring is designed or has a total of .575"+.050"=.625" between max open height and max valve spring height
.006 clearance would not normally be used or suggested as safe, youll need to know the true coil stack and true installed heights as installed

example look here

http://www.racingsprings.com/PDF/beehive.pdf

look at the first spring listed

max lift is listed as .600 lift
installed height 1.800
max lift @ 1.200 to get that .600 lift
BUT COIL STACK IS AT 1.140, thats .060 more, giving the necessary clearance

just be aware that the retainer to valve seal or retainer to valve guide or rocker slot to rocker stud or a few other clearance issues might limit what you can acctually use as lift with the valve train
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: rocker arm geometry with a new cam

Postby grumpyvette » November 4th, 2008, 10:47 am

If you can,t afford full roller rockers..the aftermarket roller tip rockers are worth the expence simply because they have LONGER slot clearance for the rocker studs and more precise ratios than stock rockers, most are forgings or cast rather than stamped liker stock,and youve stated your stock rockers bind on the studs at near full lift,the roller tips don,t do much, so don,t think thats a big deal. Image

BUT if I was going to swap rockers, a FULL ROLLER ROCKER DESIGN like I posted is well worth the extra expence as it will free up 7-10 hp MINIMUM due to lower friction alone, remember the vast amount of friction in a rocker is in the rocker fulcrum not the tip. a true roller rocker has roller bearings and an axle so the slot is replaced with a hole for the stud :thumbsup:
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


Return to Cams, Heads and Valve Trains

Who is online

Users browsing this forum: No registered users and 5 guests

cron