Valve springs

[Mark Williams]

How much pressure does a Valve spring loose during break in?

[rustbucket79]

Impossible to answer. Could be nothing, might be a small percentage. Details?

[Caprimaniac]

Hopefully not much... Some have reported 0%, but I guess it will all depend on.... Type of spring, material, etc.

[mag2555]

I have only seen defective springs drop pressure more then 5 lbs or so during break in, but the first time or Two that the motor buzzes to 6K can be a different story depending on the spring!

Are we talking a Hydro flat tappet Cam here?

[Mark Williams]

Mild hyd roller in a bbc.
PAC hot Rod springs 145 lbs seat 320 lbs open at 1.900” installed height.
Probably going to install at 1.880”

[mag2555]

If you have the needed .015" shims then I would go for 155 on the Intakes and 150 on the exh.

[panic]

My guess: springs with steeper pitch (distance between coils) will suffer more.

[David Redszus]

How much pressure does a Valve spring loose during break in?

Springs do not lose pressure because they do not produce pressure; they might lose spring force.

Spring force is determined by spring rate multiplied by the spring displacement.
A spring with a 200#/in rate, when compressed 1/2" will exert a force of 100 lbs.

Assuming that material properties have not changed, then a loss of force is due to a change in free length.

Measure the free length of a new spring. Compress the spring in a vise to solid stacking length.
Let it sit for a few days. Measure the free length and compare to the original free length.

The difference in free length multiplied by the spring rate will indicate the loss of spring force.
If the change in length is small, shims can be used to regain the target force. If large, the spring must
be replaced with a higher grade of spring.

[MadBill]

I keep meaning to put a big bolt, washers and nut through one or more p.n. springs, reef it/them down to coil bind then every six months or so remove and check installed height load, to de-bunk (my guess) or confirm the need to back off rocker arms for long-term storage.

[Roundybout]

5-7lbs loss seems the limit often cited. Is that installed height? Full lift? I'd imagine some 350lb seat springs, that amount wouldn't be much percentage wise but 120-130 seat that's starting to matter more. How important is it that the springs all match as opposed to a 5-7lb +/- variance?

[cgarb]

My personal opinion...take that for what its worth. Lol. I believe heat has more to do with springs losing tension, some poorly made springs nothing will help because of the metallurgy isn't right. Keep a good quality spring cool and within its working limits and you will be fine. Overload it with valve float or not have enough oil flow to keep the heat under control and the metal will lose its temper and get soft.