how much do valve springs get compressed when installed

grumpyvette

Administrator
Staff member
approximately how much taller is the stock valve spring when it's unloaded, compared to when installed?
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http://www.buxtonengineering.com/on_head_valve_spring_tester.php


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obviously the springs vary by engine, type of cam and application, but ID say 1/4" longer as they come out of the box , un-compressed or maybe 2" tall on average-a bit more would put you close to many applications

http://www.kmotion.biz/instht.htm

typical 2" in the box and about 1.8" installed, the spring part number load rates and ideal installed height will be in the cam spec card info
youll eventually want a few tools like a valve spring tester and spring height mics
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valve spring compressors
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http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

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

http://garage.grumpysperformance.com/index.php?threads/checking-piston-to-valve-clearances.399/

Is coil bind height and open height the same thing? The springs I'm wanting to go with have an installed height of 1.940 and open height of 1.250. With .600 exhaust lift, does that give me .090 before coil bind?
you might also want to keep in mind theres a great deal more to setting up a valve train than slapping some springs and retainers and keepers on the valves.
read thru the links and sub links as theres a great deal of useful info, that youll want to know.
btw just a bit more info, there are valve spring retainers, valve spring seats, shims, valve retainer keepers etc. that can be used that have different sizes or depths that allow you to change the installed height, or relation of the spring to the valve stem , it compressed height, or the valve springs location in relationship to the stems locking groove
keep in mind shims under the valve springs can be used to raise the spring or shorten the valves installed height, valve locks and retainers can be purchased with non-O.E.M dimensions to adjust the valves installed height or spring load rates
you use either or both depending on the application
a .050 PLUS valve lock moves the retainer .050 higher on the valve stem with no other changes, a plus .050 retainer would move the retainer .050 higher with stock valve locks or an additional .050 if matched to .050 plus locks
if you used a plus .o50 retainer with a set of minus .o50 valve locks the retainer would remain at the stock height on the valve stem

http://www.jegs.com/p/Crane/746983/10002/-1

http://www.jegs.com/p/Moroso/764349/10002/-1

http://www.jegs.com/p/Manley/940089/10002/-1

http://www.jegs.com/p/Comp+Cams/757964/10002/-1
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installed height is open height, the springs set up to provide a minimal resistance before it can be compressed further, the cam card below may help
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notice the listed info
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A BIT OF QUICK RESEARCH


Crane Cams#271-99846-16
Single Valve Springs
Outside Diameter: 1.255"
Inside Diameter: .870
Seat Pressure: 125 LBS @ 1.800"
Open Pressure: 383 LBS @ 1.200
Coil Bind: 1.100"
Rate (LBS/IN.): 428
Max Lift: .640
Set of 16

http://www.jegs.com/i/Crane-Cams/271/99846-16/10002/-1


notice the coil bind height PLUS, approximately the .090 is the listed max lift, and the max lift on the cam or open height is a bit less.
engines require clearances to work correctly and with valve springs having a bit of extra clearance helps durability, this is generally one reason WHY cams are sold with a strongly suggested set of load rates and clearances so they can operate under know and expected stress levels they were designed for
notice the listed info

lets go through it

cranesp1.png

A BIT OF QUICK RESEARCH (read these)
http://www.kmotion.biz/instht.htm

https://www.lunatipower.com/Tech/Valvetrain/ValveSpringTech.aspx

Crane Cams#271-99846-16
Single Valve Springs
Outside Diameter: 1.255"
Inside Diameter: .870
Seat Pressure: 125 LBS @ 1.800"
Open Pressure: 383 LBS @ 1.200
Coil Bind: 1.100"
Rate (LBS/IN.): 428 lbs
Max Lift: .640
Set of 16

the cam, listed with the standard 1.5:1 ratio rockers had a max valve lift of .536
with a Rate (LBS/IN.): 428 lbs x the valve spring provides about 230 lbs of resistance at max lobe lift at the lobe of .358" the cam listed never gets close to 1.100 coil bind less the .060-.090 suggested clearance, its never going to provide the max lift pressures listed or have clearance issues, as the suggested max lift is higher at .640


notice open pressure is at 1.200, for in theory, 383 lbs giving you at least in theory .100 additional clearance to coil bind , installed height is 1.800, suggested max lift is .640" but your only getting to .536" lift at the valve WITH that cam using those springs set with those clearances
Id also point out that youll want to lubricate any valve you install in a valve guide and verify the valve train clearances very carefully, and use the correct valve springs and add the correct valve seals installed
 
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