Testing: Valvespring spring rates!

36251 Views 40 Replies 30 Participants Last post by Prymer, Oct 1, 2016

GO Power Motorsports

Discussion Starter · Aug 27, 2010 (Edited)

With this being a technical forum, we felt like it would be a good idea to show how to test valve spring pressure at both open and closed heights. Testing is a simple procedure but provides insight into a crucial and often overlooked component of the cylinder head.

The installed height of a valve spring is the length of the spring when it is installed on the head with the valves closed. It is important to differentiate between the advertised installed height and actual installed height. The most common advertised install height is 40.4mm or 1.5905 inches. This does not always translate into the actual installed height on a cylinder head. It can vary up and down based on a variety of factors including wear, manufacturing tolerances, and modification. These heights are measured by the spring only, so you have to factor in the thickness of the retainer as well as the spring base when it comes to setting your spring tester.

First you will need one of these:

A spring pressure tester is a simple tool. The spring is placed between the plates and the lever is used to compress the spring. The amount of forced exerted on the lower plate is shown on the scale needle.

Next, set the stop to the installed height of the valve spring. This limits the travel of the spring tester in order to provide an accurate measurement. A set of digital calipers is used to accurately set the stop at 40.4mm.

The next step is very simple. Place spring (with base and retainer) into the spring tester, and pull the lever. Be sure to take note of the pressure before moving onto the next spring.

The next step is to set the stop for the “open” position. In these tests we used an open lift of 0.520” The .520" lift number is just an arbitrary number we used for this example as many after market cams are around the .520 lift mark. Our KSi Cams are .535" lift.

Then place the spring assembly back into the tester and pull hard. Once again make sure you take note of the pressure.

Here is a list of some of the common valve springs people are using. Each of these measurements was done with the spring’s corresponding retainers and spring bases.

Supertech 1020D Valvesprings and Retainers kit

96-97lbs on the seat (installed)
287-288lbs open at .520" Lift
Max lift .655

GO Power Dual Springs and Titanium Retainers kit

87-88lbs on the seat (installed)
239-240lbs open at .520" Lift
Max lift .665

Skunk2 Pro Series Dual springs and Retainers

73-74lbs on the seat (installed)
235-236lbs open at .520" Lift
Max lift .660

Eibach 20411.216 Dual Springs and Titanium Retainers

85-86lbs on the seat (installed)
235-236lbs open at .520" Lift
Max lift .560

Stock 2006+ Civic Si Intake

55lbs on the seat (installed)
165lbs open at .500" Lift
Max lift .500

Stock 2006+ Civic Si Exhaust

55lbs on the seat (installed)
160lbs open at .500" Lift
Max lift .500

The Skunk2 and Eibach combos were tested in 2008. The GO Power and Supertech were re-tested last week.

If you would like, we can try and obtain and test other springs that people might be interested in.

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mugen_power

· #36 · Sep 5, 2013

:thumb:

GO Power Motorsports said:
The stiffer spring rate is a double edge sword. It makes sure the valve closes however if it is too stiff it will create a loss of HP on the top end. You only need enough spring pressure to control the valve, if the pressure is too low it will have “valve float”. If too stiff you will lose power as it takes more to turn the motor to overcome the pressure.

The main function of the spring is to control the motion of the valve caused by the cam. Some cams are very gentile with open and close rates which can take lighter spring pressure, while more aggressive cams will require heavier spring rates.

The trick is to find the proper rate to control the valves while at the same time not going too light to induce valve float.

Valve float is when the rocker loses contact with the cam at high rpm due to the spring rate not controlling the motion very well. This can be seen on the dyno as a flutter and loss of power.

The main reason for high rate springs is when you have forced induction with high boost levels. If you have a spring rate of 95lbs on the seat and you are running a turbo with 30lbs of boost you effectively have 65lbs on the seat, so you will often see turbo cars run very high spring pressures 125+ on the seat to combat this.

-Jeff Giovino

Good post!

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