Author Topic: Setting up valve springs?  (Read 3399 times)

Tx-Z 302

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Setting up valve springs?
« on: September 10, 2018, 11:07:57 PM »
So what's the abridged version of how and why " setting up valve springs" ?
Chris W


Tx-Z 302

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Re: Setting up valve springs?
« Reply #2 on: September 11, 2018, 01:13:11 AM »
Learn it and use it.

https://www.youtube.com/watch?v=MsjT1rZZ90M

https://www.youtube.com/watch?v=s2aWcSIE198

http://www.kenlowe.com.au/Documents/Docs%2099%20-%20Procedure%20for%20setting%20valve%20springs%20101022-2.pdf

http://www.kenlowe.com.au/Alpha-Index.htm

Good Lord! I've built several engines in my time, degreed came, recurved distributors, etc etc etc.... But never really messed with valve springs other than getting the ones recommended for my cam?  Have I been leaving power on the table or is this a wear and tear issue?
Chris W

Stingr69

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Re: Setting up valve springs?
« Reply #3 on: September 11, 2018, 01:52:15 PM »

Not a pro here, just trying to help.
Darrell posted some good links.  Those guys are racing and do a lot of tear down, check and reassemble but maybe you will just build it once and drive?  Those guys will add shims as the spring looses pressure over time until you cant add more shims.  At that point, they replace a spring. Tear downs and checks happen pretty regularly for those guys.   

I do not do that.  Maybe pay attention to what they are doing, and just do it one time to set up your heads. 

The spring requirements are set by the cam supplier.  The required seat pressure and spring rate are what you need to keep in mind.  The "spring rate" is how stiff it is as it compresses.  The spring will provide a stiffness described as "pounds of force per inch of deflection".  How stiff is the spring?  Just math.... (Open pressure-seat pressure)/(installed height-open height) = Spring rate....expressed as "pounds of pressure/inch of deflection".  "Open pressure" comes from the "open height" spring specs, not the actual cam you are using so don't get confused.  Springs can work on more than one cam so the spring spec needs to be generic.

Installed height gives you "seat pressure".  Full actual cam lift gives you "nose pressure".  Need to have enough pressure to control the valve train but not so much that it wears or damages components.  Your valve train cost and complexity will increase as spring rate goes up. 

Add shims to provide the required seat pressure on a spring that meets the spring rate required but make sure you have at least .030" available additional spring travel available before you go into full spring bind zero space between the coils.  Watch the actual installed nose pressure to determine if you need to upgrade the studs, rockers, seals, pushrods, guide plates, etc.


 





Tx-Z 302

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Re: Setting up valve springs?
« Reply #4 on: September 13, 2018, 12:49:04 AM »

Not a pro here, just trying to help.
Darrell posted some good links.  Those guys are racing and do a lot of tear down, check and reassemble but maybe you will just build it once and drive?  Those guys will add shims as the spring looses pressure over time until you cant add more shims.  At that point, they replace a spring. Tear downs and checks happen pretty regularly for those guys.   

I do not do that.  Maybe pay attention to what they are doing, and just do it one time to set up your heads. 

The spring requirements are set by the cam supplier.  The required seat pressure and spring rate are what you need to keep in mind.  The "spring rate" is how stiff it is as it compresses.  The spring will provide a stiffness described as "pounds of force per inch of deflection".  How stiff is the spring?  Just math.... (Open pressure-seat pressure)/(installed height-open height) = Spring rate....expressed as "pounds of pressure/inch of deflection".  "Open pressure" comes from the "open height" spring specs, not the actual cam you are using so don't get confused.  Springs can work on more than one cam so the spring spec needs to be generic.

Installed height gives you "seat pressure".  Full actual cam lift gives you "nose pressure".  Need to have enough pressure to control the valve train but not so much that it wears or damages components.  Your valve train cost and complexity will increase as spring rate goes up. 

Add shims to provide the required seat pressure on a spring that meets the spring rate required but make sure you have at least .030" available additional spring travel available before you go into full spring bind zero space between the coils.  Watch the actual installed nose pressure to determine if you need to upgrade the studs, rockers, seals, pushrods, guide plates, etc.
Thanks for the info. I watched the videos in the links and understand the general principal of what he's doing.....finding values to be able to add shims over wear time to increase the usable life of the springs while maintaining his proper pressures.   I guess I'm wondering if I have a virgin head and buy a cam/lifter/ spring set. Do I still need to do this?  I bought a comp cams complete cam kit ?
Chris W

Stingr69

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Re: Setting up valve springs?
« Reply #5 on: September 13, 2018, 01:36:34 AM »
I never buy those kits.  Just never made sense to me as I end up needing to replace the stuff in the kits because I usually need different stuff.  You can try to use it.  You still need to set up the parts kit or no kit.

You must take measurements and set up the shims individually for each valve regardless of them being virgin or not.  Be sure to use the right style valves if you replace any.  If you use aftermarket retainers then this next part about o-ring seals does not apply to you. The majority of aftermarket replacement valves do not have the grooves for stock type seals so if you want run stock o-ring seals, find the valves that have the extra seal grooves (Melling valves do). 

The heads get refurbished by the shop and I assemble them myself after a thorough cleaning once they come home.  ALWAYS CLEAN ENGINE PARTS YOURSELF after the machine shop returns them to you. THEY DO NOT CLEAN THEM ENOUGH... AND THEY NEVER WILL.  All the individual spring pocket heights get measured and the shims required for each valve are calculated and written down.  Then the guides get moly paste lube inside and the heads are assembled. I like my NAPA screw down valve spring compressor best but I have several others I have used at different times. Lever style, giant C-clamp style. Preference depends a lot on the seal type I am using at the time.

67jeffreyt

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Re: Setting up valve springs?
« Reply #6 on: September 22, 2018, 06:47:51 PM »
Heck I did my own spring seats, never done em before, it wasn't hard other than buying the correct bit for my new springs, I bought shims and a spring seat tester, took time but wasn't hard to do
67 ss/rs camaro currently
68 prostreet Camaro 9.60 1/4 mile
68 Rallysport, first car high school
89 rs camaro convertible, made readers rides super Chevy

67jeffreyt

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Re: Setting up valve springs?
« Reply #7 on: September 22, 2018, 06:49:49 PM »
Completed and bolted down, car runs great
67 ss/rs camaro currently
68 prostreet Camaro 9.60 1/4 mile
68 Rallysport, first car high school
89 rs camaro convertible, made readers rides super Chevy

67jeffreyt

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Re: Setting up valve springs?
« Reply #8 on: September 22, 2018, 06:55:07 PM »
I set my springs at 120 pounds at seat pressure, per manufacturer specs.  But my room is up to .650 lift, the cutter cut my guides for a specific Teflon valve seal, and my cam is only .500 lift hydraulic roller.
« Last Edit: September 22, 2018, 07:58:34 PM by 67jeffreyt »
67 ss/rs camaro currently
68 prostreet Camaro 9.60 1/4 mile
68 Rallysport, first car high school
89 rs camaro convertible, made readers rides super Chevy

67jeffreyt

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Re: Setting up valve springs?
« Reply #9 on: September 22, 2018, 08:04:34 PM »
A stock head would use a single spring 1.25 z/spring and it is 100 psi seat pressure installed on stock components. Works up to .500 lift hydraulic flat tappet, any more cam and clearance needs checked.on retainer to guide.
67 ss/rs camaro currently
68 prostreet Camaro 9.60 1/4 mile
68 Rallysport, first car high school
89 rs camaro convertible, made readers rides super Chevy

 

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