High performance valve springs

The Lowdown on "Performance valve springs"

The valve springs pull the valves up when they are closed thereby sealing the valve. The camshaft pushes the valve open against the spring. As you can imagine this is a high wear high stress component of the engine.  They need to be fitted using a valve spring compressor - any other attempt at installing them will usually result in your chasing a spring around the garage.

If the valve spring is too strong it cause excessive wear on the cam. If it is too weak then the valve will not fully close, or at least will not close quickly enough. In a highly tuned engine you cannot afford to skimp on the selection of valve springs. If one of these breaks then the valve will stick open and this will cause catastrophic engine damage, depending on which part of the suck,bang, blow cycle the engine is at.

The springs also prevent bounce. When the valve is pulled back into its closed position the last thing you want is for it to bounce open again as it closes.

If a spring is compressed and each coil is in contact with the coils above and below you have what is known as coil bind. The spring is extremely stressed at this bind point and you should ensure that you do not approach this bind point otherwise the cam lobes, lifters and follows will be damaged.

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When you buy a valve spring it will come with 2 numbers, a height and a tension. The two should be read together and the installed height noted on the spring will exert the tension at that height. Should the installed height be different then the tension will also be different.

We recommend that you err on the site of a higher spring tension if you are unsure of the exact requirements of your rebuilt engine. When the valve springs are installed you can check for correct opening by rotating the engine through TDC and beyond for each cylinder and measuring the clearance to the piston. The overlap period is critical and you need to take careful measurements at this point. There should be a minimum clearance to the piston of 0.1" and a little more on the exhaust valves .

Incorrect oil selection, and indeed to high an oil pressure, can alter the dynamics of the valve train and therefore engine life so stick to your manufacturers recommendations. Always investigate clatter or chatter in the head of an engine as this is usually the sign of a looming problem.


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