[Neil Harvey]

I received a telephone call yesterday from a home builder asking, what Valve Springs should I use?

He made reference to some of the springs sold in the aftermarket as well as the springs offered for his engine type from Porsche.

I am unaware of the steel used in many of the aftermarket springs but have done some research into the steel used in the stock springs. If you step back and look at both, you will be hard to find any springs from any company that have failed “just” because they were poorly made. I’m sure some have as there is always some mis use, Coil bind issues and maybe one or two that slipped through QC.

More important to me is the actual application and how they are used. Not who made them. The caller made mention of watching several You tube video’s on cylinder head rebuilding which I’m sure, they all did it differently. Confusing to say the least.

There are several areas that I consider important to remember.

Not all springs for the same application are the same. The wire size, number of coils can be equal, but the rates and pressures at the seated and open dimensions can all be different.

Coil bind height is a constant. There is nothing you can do about this.

Seated pressure is all about the valve seat and valve contact and the open pressure is all about the engine’s RPM safe capabilities.

It’s easy to state the following when you have a shop full of tools. A little different when you are building in your garage with nothing more than a set of Craftsman wrenches and a floor jack.

Seat pressure is more important than installed height. Setting all the valves, with the same seat pressures is far more important than just assuming the pressures are the same by setting all the installed heights the same. Note, Intakes and Exhaust will be different.

Why, as the springs are often slightly different, equalizing the seat pressures makes sure the valve seal the same, the over the nose pressures are the same, and the engine uses the same amount of torque to open each valve. No more, no less.
But at home, all you can do is the installed height method. You then have to assume that the pressures are the same and go with the shimming to obtain the same heights.

Professionals should be looking at all the parameters when setting up springs. The retainer height should be known, valve train weights and seat and open pressures calculated, and each spring tested for its pressures at both the seated and open dimensions. The distance to the spring coil bind should also be checked. This becomes important if you are changing the cams lift numbers.

The retainer height is somewhat a fixed dimension. It’s the distance between the seat base and the underside of the spring retainer when the valve is on its seat. This can be changed with different seat depths, base thickness, retainer step differences and lock position on the valve.

Another check often forgotten is the distance between the underside of the locks/retainer to the guide seal at full valve lift when seals are installed.

A professional shop will probably have a modern digital tool providing huge amounts of data easily manipulated by changing any parameters in software. Or, something like the more common Rimac tool or its equivalent by other manufacturers. These give height and pressures only.

There is no way I can write this and find fault with any pro shop assembling cylinder heads with the installed height method. This is more the common way when using stock parts and no changes made to the cam etc. It’s your typical production shop, where time is more important than quality.

But if you are thinking about changing parts, using any aftermarket spring, spring retainer, a different cam lift, you should be checking the pressures and not just assuming all things are Ok.