Effects of higher ratio rockers on valve spring pressures.

Loves302Chevy

"One test is worth a thousand expert opinions."
I searched, but I can't find the simple answer to this question:
This pertains to a GEN 1 SB Chevy using a flat-tappet Crane CompuCam 2050. cam #114142
Cam manufacturers recommend seat and valve open spring pressures usually using 1.5 ratio rockers. I will be using 1.6 ratio rockers. Do I choose my spring and installed height based on the 1.5 ratio, and the increased pressure resulting from the 1.6 rocker is a good thing - or do I want to have the specified pressures using the 1.6 rockers?
Let me give an example: this cam calls for 114# at the seat and 318# valve open. The valve lifts are .454/.480 (1.5) and change to .484/.512 (1.6). I'm considering an Elgin spring #9914XK with the following specs: 1.260 OD single with damper, .876 ID, 125#@1.750, 325#@1.250, CB at 1.160, and .530 max lift. I calculate a spring rate of 400#/in. If I set this spring to 1.780 installed height, I get 113# on the seat and 317# at .512 lift (exhaust with 1.6). Am I doing this correctly? If I were to use the 1.6 rockers on the INTAKES ONLY, the math gets easier because the numbers would be nearly the same at .484 INTAKE and .480 EXHAUST. I have an assortment of retainers and locks to set an installed height ranging from 1.720" to 1.865" using the stock length valves.
Thanks again, Mike.
 
Re: Effects of higher ratio rockers on valve spring pressure

Id go with this option, having both valves open near .480/484 lift and use of the 1.6 ratio rockers on the intakes, Ive used that particular cam installed on several 350 and 383 engines and its a really good choice for most street cars with automatic transmissions or high 2.87-3.07 rear gears, but Id check those valve spring load rates and install heights, and valve train clearances..
generally the .600 lift Z28 valve springs work and are reasonably priced
if you change the rocker ratio the push rod alignment changes and you might need a LUIS TOOL to lengthen the cylinder head clearance slots in the cylinder heads.
be sure to check clearances carefully like coil bind,and push-rod to guide plate alignment and clearances ,verify the rocker slots don,t bind on the rocker studs as this is a common problem with stock stamped style 1.6:1 ratio rocker, verify the push rods don,t bind in the slots in the cylinder head, if they do even for an instant at one point in the rockers arc, they can bind the lifter rotation on the cam lobe and cause the cam to wipe, out the lobe and the lobe & lifter contact area resulting in a quickly failed cam,and/or restrict oil to the rockers
s
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https://sdparts.com/details/scoggin-dic ... ter/sd1005
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keep in mind all that metallic trash, cycles through the oil pump BEFORE it reaches the oil filter

many more modern oil formulations lack the correct additives for flat tappet lifters, so be very sure you check to see what oil your using and if its designed for flat tappet lifter applications
"
mike said:
The valve lifts are .454/.480 (1.5) and change to .484/.512 (1.6). I'm considering an Elgin spring #9914XK with the following specs: 1.260 OD single with damper, .876 ID, 125#@1.750, 325#@1.250, CB at 1.160, and .530 max lift. I calculate a spring rate of 400#/in. If I set this spring to 1.780 installed height, I get 113# on the seat and 317# at .512 lift (exhaust with 1.6). Am I doing this correctly? If I were to use the 1.6 rockers on the INTAKES ONLY, the math gets easier because the numbers would be nearly the same at .484 INTAKE and .480 EXHAUST. I have an assortment of retainers and locks to set an installed height ranging from 1.720" to 1.865" using the stock length valves.
Thanks again, Mike."
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

thats an excellent question,
but your question seems to be ignoring three factors , in that stated question

BTW.IF YOUR BUILDING A SBC
http://brodix.com/heads-2/small-block-chevrolet-compatible-heads/ik-series
http://www.jegs.com/i/Brodix/158/1021001/10002/-1

brodix ph# 1-479-394-1075 (ALWAYS VERIFY PART NUMBERS SEVERAL,
TIMES FROM AT LEAST TWO SOURCES, BEFORE ORDERING PARTS)

the brodix rock stud girdle is part # BR-6435 and LIST price is about $230 you can get it for less if you shop carefully
BE AWARE that the I.K. 200 heads were shipped with BOTH 3/8" and 7/16" rocker studs ,
and the poly locks for the 7/16" rocker studs ONLY fit that rocker stud girdle
obviously you need to verify what your heads have before you order the matching rocker stud girdle
Verifying your engines clearances, and rocker geometry, and use of A rocker stud girdle and high quality roller rockers go a long way towards maintaining valve train durability
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first CHEVK CLEARANCES AND GEOMETRY
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the higher rocker ratio increases the effective acceleration rate of the cams lobe ramp, being transmitted to the valve so the higher ratio tends to cause valve control issues at a lower rpm level UNLESS the valve spring load rates increased to compensate. this allows a greater area of lift or open port area so the engine will tend to run better in the mid rpm range, generally making it well worth while as the mile duration cam can use the extra lift and duration at the valve.
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http://garage.grumpysperformance.com/index.php?threads/valve-train-clearances-and-problems.528/

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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

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having a valve spring micrometer of the correct size and knowing how to use it helps a great deal
second

theres usually little or nothing gained adding 1.6 ratio rockers on such a mild cam on the exhaust so just doing the intakes makes sense

third
concerns over increased valve train or lifter and cam lobe durability at such low spring load rates IF THE PARTS ARE PROPERLY LUBRICATED AND BROKEN IN, are not particularly valid, as failures are low.I would NOT be concerned with minor increases in valve load rates that the higher ratio rockers caused as they might actually be beneficial to valve control and at the low pressure , unlikely to effect durability


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Re: Effects of higher ratio rockers on valve spring pressure

So, in a nutshell, increasing the seat pressure would be more beneficial for valve control issues at lower rpms, rather than the resultant increase to the valve open pressure when using higher ratio rockers. Correct?
 
Re: Effects of higher ratio rockers on valve spring pressure

Loves302Chevy said:
So, in a nutshell, increasing the seat pressure would be more beneficial for valve control issues at lower rpms, rather than the resultant increase to the valve open pressure when using higher ratio rockers. Correct?

I had to read that about five times before I think I understand what your getting at,
what I,m saying , in the previous post,is that a slight increase in seat pressure, over that 113 psi level you posted, tends to help valve control (SO I d have no problem with seat pressures near 120 lbs)and a slight increase in open pressure resulting from increased valve lift, to near the 250- 270 lb level at full open with the 1.6:1 ratio rockers on the intake only, is not going to be a problem and may even be helpful because of that particular cams fairly low duration and lift in that application. Id be far more concerned with maintaining all the clearances and rocker geometry
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http://www.wallaceracing.com/rockercalc.php

http://www.pontiacstreetperformance.com/psp/RockerArms.html
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graphing out the change in lift at the valve with a
1.5:1 vs 1.6:1 ratio rocker valve lift diagram would look similar too this
Rocker Arm Ratio Explained
You've heard of 1.5:1 ratio and 1.6:1 ratio rocker arms. What does that really mean? How can you make more horsepower by using the larger ratio rocker arms?

The ratio of a rocker arm refers to the amount of movement on the valve side of the rocker arm in comparison to the pushrod side. A 1.5:1 rocker arm will move a valve 1.5 times the lift of the cam, assuming all things are in proper working order. If your cam has a lift of .4 inches, multiply by 1.5 to get .6 inches of actual valve movement. With the same cam lift of .4 inches: If you do the math on a set of 1.6:1 rocker arms: Multiply 1.6 x .4 inches of cam lift. You get .64 inches of actual valve movement. Essentially, changing to a larger ratio rocker arm is the same as increasing the lift of your cam the same amount. Opening both valves further usually is a benefit in the power department as your engine is capable of moving more air and exhaust through it.
 
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Re: Effects of higher ratio rockers on valve spring pressure

So I bought 8 new 1.5 ratio rockers to use on the exhausts and I will re-use the 1.6 ratio on the intakes (only 19K miles). This gives valve lifts of .484 IN and .480 EX. I'm going with that Elgin spring, so the seat pressure (at 1.770) should be 117# and 309# valve open.
I know it's more work than using low-ratio rockers, but since I have a new set of "stock" pressure springs, retainers, and locks that will fit in the spring pockets, I will use them for break-in. They should give about 77# at the seat and 202# valve open. I break the engine in on my test stand for 20-30 minutes and never rev over 3000 rpm.
The instruction sheet that came with the new rockers said to use new pushrods because the ends and rocker arm seats have to mate to each other - just like a cam lobe and lifter. Do I really need to? They only have about 10K miles and are TrickFlow 5/16" .080 wall 7.800" one-piece hardened chrome moly. And, of course, moly paste will be used, the engine will be pre-lubed, and the valvetrain geometry will be perfect. Thanks, Mike.
 
Re: Effects of higher ratio rockers on valve spring pressure

Loves302Chevy said:
So I bought 8 new 1.5 ratio rockers to use on the exhausts and I will re-use the 1.6 ratio on the intakes (only 19K miles). This gives valve lifts of .484 IN and .480 EX. I'm going with that Elgin spring, so the seat pressure (at 1.770) should be 117# and 309# valve open.
I know it's more work than using low-ratio rockers, but since I have a new set of "stock" pressure springs, retainers, and locks that will fit in the spring pockets, I will use them for break-in. They should give about 77# at the seat and 202# valve open. I break the engine in on my test stand for 20-30 minutes and never rev over 3000 rpm.
The instruction sheet that came with the new rockers said to use new pushrods because the ends and rocker arm seats have to mate to each other - just like a cam lobe and lifter. Do I really need to? They only have about 10K miles and are TrickFlow 5/16" .080 wall 7.800" one-piece hardened chrome moly. And, of course, moly paste will be used, the engine will be pre-lubed, and the valvetrain geometry will be perfect. Thanks, Mike.

Ive never had an issue re-using old push rods on new roller rockers with a good dose of moly cam lube on the tips , AS LONG AS the tips looked like they were in decent condition and not obviously worn,after, they passed a close inspection before they were used, most good brand name aluminum roller rockers have pressed in hardened steel push rod seats that are far less likely to wear than the tips of the push rods.
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OBVIOUSLY that assumes you have no valve train clearance issues, binding or geometry or lubrication issues, and you set the lash or lifter pre-load on the valve train correctly and use the correct oil, and it certainly would help any engines durability to have provisions for adequate valve train oiling and a bit extra valve train cooling can be helpful on an engine designed for higher rpm use.

READ THRU THE LINKS


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Re: Effects of higher ratio rockers on valve spring pressure

as with most things theres a trade off in quality,durability,and features and cost,if your looking to keep cost low , stock stamped rockers and rocker balls sets are available
http://www.summitracing.com/parts/sum-g ... /chevrolet

http://www.superchevy.com/how-to/vemp-0703-corvette-rocker-arms/
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you can upgrade to roller tip 1.6:1 ratio for a few bucks more
http://www.summitracing.com/parts/sum-141507
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proform has cheap import roller rockers
http://www.summitracing.com/parts/pro-6 ... /chevrolet
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AND a slightly better version
http://www.summitracing.com/parts/pro-6 ... /chevrolet
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summit racing sells low cost sets of roller rockers
http://www.summitracing.com/parts/sum-g ... /chevrolet
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http://www.crower.com/media/pdf/2008b/153-155.pdf

http://www.lunatipower.com/Tech/Valvetrain/HowToVerifyValvetrainGeometry.aspx
keep in mind all roller rockers do not have identical dimensions, crower offers .050 off set trunion designs ans the designs dimensions do differ slightly between manufacturers
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keep in mind that trade off in durability and cost and remember that as the valve spring pressures and rpms go up the durability tends to go down simply because the loads,stress levels and heat tend to increase rapidly, as those factors are increased.
it rarely makes sense to buy the least expensive components you can find as long term durability tends to be absurdly low
 
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Re: Effects of higher ratio rockers on valve spring pressure

the better brands may cost more but they also tend to be made better and durability tends to be better, making the $100-$200 you saved on cheaper rockers look like a really bade bargain when one comes apart at 6000rpm resulting in damage that might have been avoided
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http://www.summitracing.com/parts/tfs-3 ... /chevrolet
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http://www.summitracing.com/parts/cca-1 ... /chevrolet

http://www.summitracing.com/parts/cca-1 ... /chevrolet
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http://www.summitracing.com/parts/crn-1 ... /chevrolet
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Rockabilly said:
@ boogie & 77_cruiser,

thank you for following my topic.
I would like to ignore the pushrod length checker tool too, but I'm afraid it's going to become a problem one day.


@ grumpyvette,

If I respect the tool, the rocker arm position looks strange (from my point of view).

I mean the quite short end of the pushrod above the guide plate (especially the intake valve ~ 0,5 inch).

Furthermore it seems not to be possible, to reach the 90°-ratio --> rocker arm to valve on mid lift.
(Maybe I'm wrong and it's only a visual mistake)
What do you think, should I still follow the tool and use shorter pushrods?

Intake / Stock Pushrod
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Exhaust / Stock Pushrod
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Intake / Adjustable Pushrod
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Exhaust / Adjustable Pushrod
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Intake / Distance To Guide Plate
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Exhaust / Distance To Guide Plate
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Intake / Mid Lift Ratio Possible?
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Exhaust / Mid Lift Ratio Possible?
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I run into similar questions all the time, while building engines and the first thing Ive always done is to get on the phone to the tool manufacturer and ask the tech guys,if I have questions simply because asking questions beets replacing busted parts every time!
while I agree that the valve stem wear marks the rockers are making look to be correct and I see no indication the valve trains binding Id also point out that the checker indicates or at least is designed to indicate the OEM SPECS as to the rocker to push rod and rocker stud locations, I,d also point out you have swapped to AFTERMARKER ROLLER ROCKERS so that push rod check tool may no longer be valid, with those rockers in use.

what to look for and having had that issues many times in the past I can assure you that the first thing they usually ask is if the cylinder heads are completely OEM,/stock and if you have changed any component parts or altered the valve spring installed height.


its hardly surprising when getting your rocker geometry's a challenge, its not like they make it standard or easy
ERSON,CRANE and CROWER tend to have good consistent dimensions
and some of the off shore imports are a joke in consistency
comps rockers rocker angles vary a good deal between models, but all can be made to function
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link to tool,
http://www.summitracing.com/parts/man-42133/overview/

http://www.manleyperformance.com/contact.shtml
Phone (732) 905-3366
heres the instructions that come with the tool, posted below and if you call them they will tell you it will only work with stock chevy OEM BIG BLOCK PRODUCTION CYLINDER HEADS, not many aftermarket heads as many have the valve angles changed or the heads deck surface rolled a few degrees
manley said:
This is a very simple tool to use:

Rotate lifter to cam base circle and slide the tool over the rocker stud.
One of the ears on either side of the tool will rest on either the valve tip or the pushrod.
If the tool rests on the valve tip, you will measure the gap left between the pushrod and the end of the tool. This distance will be added to the existing pushrod length for the new length needed for correct geometry.
If the tool rests on the pushrod, and there is a gap between the tool and the valve tip, you will subtract the distance from the existing pushrod length for correct geometry.
Works great with a pushrod length checking tool.
 
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