valve spring selection

[AdamVR4]

After doing some searching, it appears that our community is pretty damn ignorant of the springs we put in our heads.

I currently think that I want springs that meet the following constraints:
1) small enough wire diameter to avoid coil bind with aftermarket cams
2) as close to stock stiffness as possible to avoid timing belt problems (overwhelmed tensioner, eccentric pulley loosening)

Determining #2 is difficult by itself because stiffness (k) data is so limited. You're lucky to find it presented like this:

the stock valve seat pressure is 52.9 lbs at an installed height of 1.492", free height of 1.83 for '93+ cars

This drive me nuts because that's a force, not a pressure, and the free height is often not provided, so you can't calculate a stiffness.

But in this case, stiffness, k = 52.9 lbs / (1.83"-1.492") = 156 lbs/in

The only other reliable spring data I can find is from 3SX!

k, 3sx = (they actually give us 2 data points!) = 280 lbs/in

From here, all you would need is the spring mass, retainer mass, and valve mass to calculate the first natural frequency of the valve spring assembly. Does anyone know them?

efunda claims you want the first natural frequency of the valve spring assy to be 15 to 20 times greater than the cam frequency to avoid a reduction in spring stiffness as RPM's increase. Based on the following, I guess that sort of stiffness is excessive in automobiles.

If the engine is running at 8000 rpm's, the cams are at 4000 rpm's ... divide by 60 ... 66.67 cycles per second ... ~67 Hz

Without data, I'm assuming a valve assembly weight of 100 grams (If I recall from dynamic systems, you only include a portion of the spring mass, but it's been a while...?). The natural frequency is then calculated using:


(source)

If you're doing the calculations in USCS, use lb/ft for stiffness and slugs for mass. In SI, use N/m and kg.

natural frequency given an assumed assy mass of 100 g's:
fn, oem = ~83 Hz
fn, 3sx = ~111 Hz

Can anyone dig up more data for me? Crower springs? Brian Crower springs? IPS? Dynamic? Masses of ANYTHING? haha ... Similar analysis done for DSM's or Supras?

Thanks,
Adam

[Hans@GZP]

Brian Crower Valve Spring Kit | Ground Zero Performance

Supertech Valve Spring Kits | Ground Zero Performance

[AdamVR4]

natural frequencies still based on 100g valve/spring/retainer assembly assumption...

OEM - k: 156 lbs/in... fn: 83 Hz
3SX - k: 280 lbs/in... fn: 111 Hz
BC - k: 275 lbs/in... fn: 110 Hz
STstiff - k: 267 lbs/in... fn: 109 Hz
STsoft - k: 254 lbs/in... fn: 106 Hz
STdual - k: 323 lbs/in... fn: 120 Hz

If any of this sounds wrong, please, speak up.

[Boostaddict]

I comprssion tested a handful of springs (stock, crower, web dual, beehive) and posted the compiled data at 3stech. Search beehive.

[green-lantern]

This isn't really relevant to the info you're looking for but I thought it was a pretty good read.

The Spring that Revolutionized Nascar - 2012 Daytona 500 - Popular Mechanics

[AdamVR4]

I comprssion tested a handful of springs (stock, crower, web dual, beehive) and posted the compiled data at 3stech. Search beehive.

I found that but you said the x axis (deflection) was misleading and technically incorrect. If you can clarify that I can use your data.

[DocWalt]

In for info.

[Boostaddict]

I found that but you said the x axis (deflection) was misleading and technically incorrect. If you can clarify that I can use your data.

I have all the data still. I believe it was just the X axis label that was misleading. It should have simply been called deflection not deflection from installation height or something. I'll look at the excel data in the next day or so and let you know. Shoot me an email address if you want a copy. Not sure I still have your cell # or not.

W.

[AdamVR4]

I would have updated this thread last night, but as I was going through boostaddict’s data, I noticed that the springs almost universally exhibit some non-linearity. Specifically, our valve springs are less stiff between their free height and installed height than they are between the installed height and (approaching) bind.

If it weren’t for the OEM springs, I probably wouldn’t have noticed this. Based on the OEM engine manual data for ‘93+ springs, you can determine the stiffness in the free to installed height range. Over the same deflection range, boostaddict’s data nearly matched this. His old springs are actually a hair stiffer than ‘93+ OEM (perhaps he tested the ‘91-‘92 springs? They have a different free height than 93+; I need to review this later). However, over the entire deflection range, his old OEM springs were considerably stiffer than the 93+ (in the free to installed height range).

As expected, the conical kiggly springs are very non-linear, so I won’t be including them.

Bottom line, I need to make sure the stiffness data is all taken from similar deflection ranges. Given the relative availability of stiffness data in the free to installed height range, that’s probably what I’ll use.

Also, I was able to find mass data for 1G DSM springs, retainers, valves, and keepers. The total was a little higher than my assumed 100 grams (~125 grams or so).

[Boostaddict]

I believe the stock springs I measured were out of my orginal '93 heads with 100k+ miles, but I've had so many heads laying around and so much intermixed OEM valvetrain hardware (boxes full) that they could easily be newer ones that I purchased used at some point over the past decade or more.