What is accepted tolerance for new aftermarket valve springs?

[70Hardtop]

Hi all,

I had the opportunity to be able to use a near new Rimac valve spring tester for a few days (the digital version). The Top Alcohol dragster paid A$1200 for it and it is a marvelous piece of equipment. After reading someone's complaint about Comp Cam valve springs not being true to their claimed values I decided to test a new box of Comp CC-996-16 double springs that I had bought about 4-5 years ago but never used.

First of all, I was confused by the label on the box which stated that pressure at 1.15" was 366 lbs. As I was not getting anywhere near that, I called up Comp cams and asked about that; he said, oh that must be a typing error, it is supposed to be 336lbs.

Pressure at 1.7" was claimed at 115.
Pressure at 1.15" supposed to be 336

I tested each spring and the numbers were way out. Only two springs were close to claimed value, and only for open pressure. 333 and 334. All seat pressures were 120-128pounds

Open pressure values varied mostly from 328 to 334 with one being 347.

My question is, what is an acceptable tolerance for a middle quality brand of double spring like Comp Cams? I would say that these values are not very consistent with their claims. Should the buyer need to shim springs to get the desired consistent loads? I wouldn't think so.

I also tested a box of used (but near new) Trick Flow single springs (standard performance upgrade TFS-942-16)

Specs: 1.7" /1.2" 115 /285 lb

All springs except one were within 2-3 pounds in both ranges

 

[yellow rose]

When you get into the better springs...they are usually between 5 and 10 percent higher than the spring is called out for. This compensates for pressure loss when the springs go through their first few heat cycles.


For what you are testing I wouldn't worry about it. Shim a bit if have to. I've never really been concerned about the pressures as much as I am the spring rate. What I've found is the cheap springs don't have the spring rate they should. IOW, if you are 5% down on installed height and open pressure is the spring rate what they should be. If not, get new springs. If the rate is correct then shim them a bit and go.

 

[Hellrats]

You get what you pay for. I have shimmed many a Comp Cam valve springs over the years to get the pressures correct. I don't buy to much of there stuff anymore. There are better options out there and I hate having to do thing over.

 

[crackedback]

What process did you use when testing?

Did you load the spring in the rimac and go? Or did you do anything else prior to pulling the lever?

 

[MOPAROFFICIAL]

Hi all,

I had the opportunity to be able to use a near new Rimac valve spring tester for a few days (the digital version). The Top Alcohol dragster paid A$1200 for it and it is a marvelous piece of equipment. After reading someone's complaint about Comp Cam valve springs not being true to their claimed values I decided to test a new box of Comp CC-996-16 double springs that I had bought about 4-5 years ago but never used.

First of all, I was confused by the label on the box which stated that pressure at 1.15" was 366 lbs. As I was not getting anywhere near that, I called up Comp cams and asked about that; he said, oh that must be a typing error, it is supposed to be 336lbs.

Pressure at 1.7" was claimed at 115.
Pressure at 1.15" supposed to be 336

I tested each spring and the numbers were way out. Only two springs were close to claimed value, and only for open pressure. 333 and 334. All seat pressures were 120-128pounds

Open pressure values varied mostly from 328 to 334 with one being 347.

My question is, what is an acceptable tolerance for a middle quality brand of double spring like Comp Cams? I would say that these values are not very consistent with their claims. Should the buyer need to shim springs to get the desired consistent loads? I wouldn't think so.

I also tested a box of used (but near new) Trick Flow single springs (standard performance upgrade TFS-942-16)

Specs: 1.7" /1.2" 115 /285 lb

All springs except one were within 2-3 pounds in both ranges

I'm very picky of where I get my valve springs from, comp is not my favorite.
It's short for "comp'lete garbage"
Use pac or k motion, crane used to be good.
Paw used to sell a real nice double that gave 160 seat and 340 open in a sb height.

 

[Wyrmrider]

PAW
I went through Speed-O-Motive
I have a spring tester and the ISKy checking spring
I use Isky spring cus I get the long deal on them
and Speed-O is gone and PAW- the so cal one? did you use the WayBack Machine?

 

[70Hardtop]

PAW
I went through Speed-O-Motive
I have a spring tester and the ISKy checking spring
I use Isky spring cus I get the long deal on them
and Speed-O is gone and PAW- the so cal one? did you use the WayBack Machine?

Sorry, I can't make any sense out of what you wrote there. I understand each word on it's own but not any of those sentences.

 

[70Hardtop]

I'm very picky of where I get my valve springs from, comp is not my favorite.
It's short for "comp'lete garbage"
Use pac or k motion, crane used to be good.
Paw used to sell a real nice double that gave 160 seat and 340 open in a sb height.

Thanks for reply, I am beginning to see that Comp is not as good as they claim. They may make good camshafts (or made in the past, as that's where they began) but perhaps their springs are a bit second rate (excuse the pun).
The TrickFlow springs I mentioned were all within a few pounds of claimed. And are they not made by PAC? They were all over 12 years old, EXCEPT one I bought a month ago from Summit, to replace a missing one - that one was well over in pressures. But as Yellow Rose mentioned, perhaps that is normal until it has gone through its first few heat cycles.

 

[70Hardtop]

What process did you use when testing? Did you load the spring in the rimac and go? Or did you do anything else prior to pulling the lever?

I'm not sure what you mean by process. Yes I just tested them. They are new. I put them into the Rimac twice, in two runs (after setting each height stop) to check both the claimed values: one for 'seat pressure/installed height' of 1.7" and one for open pressure of 1.15". I used the correct retainer and measured that and deducted that height from the reading to get the actual spring height /load.

In hindsight, after reading what Yellow Rose said, maybe it would have given a more truer set of readings if I had run them in an engine for a few hours first.

But that option was not available.

I also swapped around quite a few inners and outers to see if the readings changed, which they did a little in some cases.

I will just shim to get a more even set, and won't buy Comp anymore

 

[70Hardtop]

When you get into the better springs...they are usually between 5 and 10 percent higher than the spring is called out for. This compensates for pressure loss when the springs go through their first few heat cycles.


For what you are testing I wouldn't worry about it. Shim a bit if have to. I've never really been concerned about the pressures as much as I am the spring rate. What I've found is the cheap springs don't have the spring rate they should. IOW, if you are 5% down on installed height and open pressure is the spring rate what they should be. If not, get new springs. If the rate is correct then shim them a bit and go.

Thanks for reply, and no I am not a journalist. I see the spring rate values given but I am not sure how to test that. It would have been nice if these Comp springs WERE 5-10% over as you say, but they are all under (except one, which was way over at 347#). It would be interesting to see the values after they had been run in an engine for a few hours. But I don't have that luxury. I will contact Comp and see what they say about it. But I don't expect much interest from them.

 

[yellow rose]

Thanks for reply, and no I am not a journalist. I see the spring rate values given but I am not sure how to test that. It would have been nice if these Comp springs WERE 5-10% over as you say, but they are all under (except one, which was way over at 347#). It would be interesting to see the values after they had been run in an engine for a few hours. But I don't have that luxury. I will contact Comp and see what they say about it. But I don't expect much interest from them.

If you know the spring rate, you can verify that by the pressure on the seat and pressure at max lift. If the spring rate is correct that's a big deal.

I should mention you should ALWAYS check spring loads with the exact retainer you are going to use. It will affect the loads. You should never check spring load without a retainer.

 

[70Hardtop]

If you know the spring rate, you can verify that by the pressure on the seat and pressure at max lift. If the spring rate is correct that's a big deal.

I should mention you should ALWAYS check spring loads with the exact retainer you are going to use. It will affect the loads. You should never check spring load without a retainer.

thanks, I did some research and found the formula for finding the spring rate. (open pressure - seat pressure) /the cam lift at valve. Which for my cam (Comp XE275HL-10) is 0.525". These are the springs recommended by CC for that cam and the advertised spring rate is 402 lbs/in. I just worked out 5 of these springs and all are under. The closest is 396 lbs/in and the worst (2 springs are that) is 388 lbs/in. I will work them all out later but I expect them to be all under. I wouldn't expect the springs to improve in stiffness after running in so it's a pretty dismal result. And yes, I didn't mention in the OP that I used the correct retainers for those springs but I mentioned it in another reply post.

 

[nm9stheham]

That spread in rate is not all that huge; that is a total spread of 8 lbs, which is +/-1% from the mid range value. I would not call that dismal; I'd call it normal manufacturing tolerance.

And some potential difference will be in the measurements; just because the gauge has a nice digital readout does not mean anything about the accuracy of the equipment's calibration that you are using. If that equipment is calibrated 2% differently that the Comp equipment, then that would show the difference in you mid-range rate value vs the Comp number.

Then there are minute variations in the spring wire that are going to effect the rate too. It may seem hard to believe, but just a .001" change in the spring wire diameter will make a >2% change in spring rate for spring wire of this diameter range.

 

[70Hardtop]

That spread in rate is not all that huge; that is a total spread of 8 lbs, which is +/-1% from the mid range value. I would not call that dismal; I'd call it normal manufacturing tolerance.

Hi, I agree with what you say and there is certainly a lot of science in it. As an instrument fitter myself, I am familiar with tolerances (and you are right that the fancy digital readout does not change the accuracy, but does fool many people!) But don't forget that I also checked a set of Trick Flow springs and all (except one) were within 2-4 pounds of spec. Which is pretty well right on. The one that wasn't was a new replacement spring I bought last month, same part number but totally different batch number (as in approx 12 years apart). And the older ones were run in but only around 1 year use. So I would say that that gives a good baseline for accuracy and the Comp springs were all over the place in terms of variations. As they are new and after run-in I would expect the values to drop a little and since they are all under in the first place, I would still consider that to be on the dismal side.

Unfortunately I won't have access to the Rimac when I assemble the 340 heads so won't be able to shim them too accurately. I do have my own home made valve spring tester but it is only good for springs upto about 300 pound

 

[yellow rose]

That spread in rate is not all that huge; that is a total spread of 8 lbs, which is +/-1% from the mid range value. I would not call that dismal; I'd call it normal manufacturing tolerance.

And some potential difference will be in the measurements; just because the gauge has a nice digital readout does not mean anything about the accuracy of the equipment's calibration that you are using. If that equipment is calibrated 2% differently that the Comp equipment, then that would show the difference in you mid-range rate value vs the Comp number.

Then there are minute variations in the spring wire that are going to effect the rate too. It may seem hard to believe, but just a .001" change in the spring wire diameter will make a >2% change in spring rate for spring wire of this diameter range.

Hi, I agree with what you say and there is certainly a lot of science in it. As an instrument fitter myself, I am familiar with tolerances (and you are right that the fancy digital readout does not change the accuracy, but does fool many people!) But don't forget that I also checked a set of Trick Flow springs and all (except one) were within 2-4 pounds of spec. Which is pretty well right on. The one that wasn't was a new replacement spring I bought last month, same part number but totally different batch number (as in approx 12 years apart). And the older ones were run in but only around 1 year use. So I would say that that gives a good baseline for accuracy and the Comp springs were all over the place in terms of variations. As they are new and after run-in I would expect the values to drop a little and since they are all under in the first place, I would still consider that to be on the dismal side.

Unfortunately I won't have access to the Rimac when I assemble the 340 heads so won't be able to shim them too accurately. I do have my own home made valve spring tester but it is only good for springs upto about 300 pound

nm9 is correct for those springs less than 1% spread on rate is pretty good. As you go up in spring quality you find the spread goes down.

I'm so DAMN glad you put forth the effort to search out the math on spring rates and did your own research and math.

I'd rather lead you to it than tell you how to do it. That way, you learn (not that you are stupid but it seems to me those who do their research do better) and you can pass it on.


NICE JOB!!!!!!

 

[crackedback]

I was getting at the shorter inner and have seen people test multi spring untis without a retainer. Looks like you were correct in your test set up.

 

[70Hardtop]

I was getting at the shorter inner and have seen people test multi spring untis without a retainer. Looks like you were correct in your test set up.

yeah, but I did make that mistake at first! Was testing them without a retainer - (still 'green' haha) Until a fellow in the machine shop pointed out that the inner spring needs the retainer to give the complete even load.

 

[70Hardtop]

nm9 is correct for those springs less than 1% spread on rate is pretty good. As you go up in spring quality you find the spread goes down.

I'm so DAMN glad you put forth the effort to search out the math on spring rates and did your own research and math.

I'd rather lead you to it than tell you how to do it. That way, you learn (not that you are stupid but it seems to me those who do their research do better) and you can pass it on.NICE JOB!!!!!!

I agree 110% with you there. I am also sick of spoon feeding people and with 90% of the population, you tell them something and mostly less than half of the info (if that) will be retained. The best way people will learn is if they make the effort to find out, or discover, for themselves.

 

[crackedback]

Always good to have someone watching out for you!

 

[Wyrmrider]

and if there is a step on the seat if duals- most of the time you machine the step off especially on short springs like LA and Pontiac, but see if it was done if the spring calls for it

 

[4spdragtop]

Subscribed and thanks for taking the time to post. I have a set of CC springs in the 273 I was going to swap over to the 340 when it's ready. Good info.

 

[70Hardtop]

and if there is a step on the seat if duals- most of the time you machine the step off especially on short springs like LA and Pontiac, but see if it was done if the spring calls for it

Had not thought about that, but will check. Petty sure they are machined flat.

 

[70Hardtop]

Subscribed and thanks for taking the time to post. I have a set of CC springs in the 273 I was going to swap over to the 340 when it's ready. Good info.

thanks, yes it would pay to check them, if they are CC duals and they have been run in and are still fairly fresh, I would be interested in seeing the numbers. I made up a basic spring tester at home with a drill press and some digital bathroom scales (I would assume reasonably accurate since they are graduated in 100gram lots.) I put a 440 intake valve into the drill chuck and set the depth pointer to zero at the installed height, measured with a digital vernier. Valve head was pressed down on the valve and different thickness washers used under the valve to bring it to height. Then zero'ed. Seem to give fairly consistent readings with some practice.

 

[4spdragtop]

The springs we installed were singles with damper. 901-16 I believe. Have caused no issue in the 273 but was on the fence whether to reuse on 340. They are 6 years old with maybe 15k on them.
Once I have a few more beers I'll see if I can duplicate your tester lol.
Thanks for the info/tips!

 

[70Hardtop]

The springs we installed were singles with damper. 901-16 I believe. Have caused no issue in the 273 but was on the fence whether to reuse on 340. They are 6 years old with maybe 15k on them.
Once I have a few more beers I'll see if I can duplicate your tester lol.
Thanks for the info/tips!

you're welcome and here are some pics of the setup - it aint no Rimac but with practice it was not too bad for ball park figures. The newspaper is just there for protection - between the heavy plates and the glass top of the scales. That was an early experimental setup - I have since moved the plates underneath - they are there just to give some height and stability. (scales are in kgs, not pounds!)