What Are Valve Spring Shims?

What is the function of a valve spring shim?

The shims are to make that measurement the same for every valve. It’s especially important after a valve job /hardened seat install when the installed height can be changed based on the ammount that the valve or seat has been ground.

What happens when valve spring tension is too high?

If the spring pressures are too high, the added friction will result in: More heat, Faster valvetrain wear, Potential failure of other valvetrain parts (i.e. rocker arms, pushrods, etc.), and.

What happens when valve spring tension is too low?

If spring tension is too light, valve float and eventual engine damage can occur. According to cam experts, one of the most common causes of premature camshaft failure is the use of improper valve springs. This can include too high or too low spring pressure, or the springs can just be plain worn out.

How do I choose a valve spring?

Selecting a Spring Use only the valve springs that will give the correct spring pressure with the valve both on the seat and at maximum lift. The outside diameter of the recommended valve spring may require that the spring pocket of the head be machined to a bigger size.

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Do heavier valve springs add horsepower?

We have done A-B-A engine dyno tests, and you do not lose HP with heavier springs. However, too light (seat pressure) can be VERY bad for the valve train, especially the roller lifters themselves.

What causes valve spring failure?

What Can Cause Valve Springs To Fail. To maintain correct valve operation at normal engine speeds; all of the valve springs must exert a certain amount of spring pressure. Consequently, too low or week valve spring pressure; may cause valves to not completely seal or float under higher (RPM).

Can you have too much valve spring pressure?

Yes, too much spring pressure will damage parts. As you have seen first hand. Too much seat pressure will collapse lifters and cause valves to float as well.

Can you stack valve spring shims?

Stacking shims won’t hurt a thing. As long as the spring is sitting on a flat hard surface and has some way of establishing a stable spring pocket to keep it in proper relationship to the valve stem.

How do you break in a new valve spring?

To properly break in your newly installed valve springs, run your newly installed valve springs through one heat cycle at a maximum of 1,500-2,000 rpm until the engine warms up and then let your engine cool down.

Are stiffer valve springs better?

Higher spring rates mean greater force on the camshaft and consequently more resistance to rotation. The flip side to this argument is that stiffer valve springs control the valves better at high speed and provide better prevention of bouncing valves, which can create more power.

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What are the symptoms of a broken valve spring?

Broken or weak valve springs in an engine can cause many different drivability and performance problems. Broken valve springs cause excessive valve noise, compression loss and can cause severe internal engine damage.

What does a bad valve spring sound like?

Re: What does a broken valve spring sound like? At idle it will most likely sound fine. When you drive it “normally” it will sound like you have an exhaust leak (“tick”) and will sputter and hesitate. If you floor it it will backfire and sould horrible.

How often should you change valve springs?

It is recommended to check ALL spring pressures once a year or every 15K miles. That does not mean they will need replacing, that is proper maintenance. Depending on the lobes used and if properly installed, certain springs can last 30+k, some less some more.

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