comp cam 980-12 89lbs or 980-12 91 lbs valve springs, what is the difference?

[evil666]

I just got some comp cam 980 91 lbs valve springs and want to know if these are ok for my car with a stock cam. A lot of guys on this forum use the comp cam 980 89 lbs, and want to know what is the difference, and if the ones I bought are still fine. I am not a pro in valve springs, so I don't know if 89 or 91 lbs make a big difference, I just want to make sure I don't chop my cam.

Thanks for any info.
Marco

86 Grand National t-top (59900km)
stock long block,stock suspension, red stripe convertor, te44, smc alk injection, 24lbs boost, 94 octane, hooker cat back with dyno max ultra flow muffers, tomco 30lbs injectors, dynotech stage 4 street chip, thdp, mease 24 row IC, Ron Custom max boost brake module, MT drag radials (275/50/15) 3800lbs race weight with driver.
BEST E/T
60FT=1.52
1/8= 7.38
I/4= 11.74
MPH=113
BESTmph=114

 

[49-blues]

2 lbs.

 

[87LtdT]

Didn't know there was a difference....thought CC 980's were all supposed to be 91 lbs at 1.700" nominally with of course some variation around the nominal. Even if they do have 89 and 91 lb versions of CC980 springs either should be OK...IMO. Just be sure to get 12 that are 89's or 12 that are 91's...don't mix them. I measured 12 91's many years ago and found their standard deviation to be 1.34 lbs.

Although I'm sure there are good results....the one's I'd stay away from are LT-1's (advertised at 104 lbs) and CC981's (advertised at 105 lbs)...these to me appear to be too stiff and could damage a cam lobe.

HTH, Bob

 

[87GN_70GS]

I'll bet a dozen donuts if you were to measure a set, you'll find anywhere from 87 to 93 lbs. Don't know that a valve spring load checker will even be repeatable to 2 lbs., let alone accurately display 2 lbs. diff.

 

[87LtdT]

I'll take that bet and raise you a half gallon of chocolate milk

Set the 1.700" height with joe blocks, used 2 different spring testers, both routinely calibrated and got virtually identical results. But not the results I expected!!

980's were new and advertised at 91 lbs at 1.700" and I got a high of 80 (1 piece...next high was 77) and a low of 74 (1 piece)....13 of 16 were either 75 or 76 lbs at 1.700"...on both spring testers. I'm confident in the machines, my repeatability, and I could read the gauge easily enough within +/-1 lb. Std dev = 1.3.... .7 if you threw out the single 80.

At same time I measured a set of new 979's...averaged 73 lbs...advertised at 80. Std dev = 1.8

Also measured a set of LT-1's I'd just purchased from Jack Cotten. Found them to average 99 (104 advertised) with 2.0 std dev.

Measured my 30k mile stock springs and found them to be 68 with std dev of 1.7.

I spoke with Comp Cams a lot about why my measurement numbers (remember from 2 different calibrated tools) were so much lower than their advertised. They of course didn't believe my numbers...

To this day I don't know what to make of this wide discrepancy....I'm satisfied with technique, equipment and accuracy. Did this in 2000....installed the 980's and never had any trouble.

Fyi...Bob

 

[87GN_70GS]

Spring rate is a factor of shear modulus, wire diameter to the 4th, overall mean diameter to the 3rd, and number of active coils. If we assume that the springs were made from the same lot of steel so that the modulus is the same, then small variances in wire and mean diameter can make an impact on rate. And if free length is off by a bit, then the spring force numbers will also be off. So it's not hard to see that you're going to get some variations in your measurements. Comp may have actually gotten the numbers they were claiming...once....long ago. They may have switched vendors, or the forms used to roll the springs may have migrated...or the sun was in their eyes.

 

[VadersV6]

All the springs may not be from the same exact batch of metal. You can have a little variance in the temper, which will affect not only the installed pressure and rate, but the lifespan. You may have a slight difference in wire diameter...like just a few thousandths, which would affect pressured like that. Back in the engine building days, I never used to see variances like that with new springs. Too bad that quality control has taken a nosedive with the aftermarket. Usually, manufacturers have to outsource their parts, (multiple spring manufacturers) and/or buy their materials from several different vendors just to meet quotas. OEM springs will tend to be the most consistent though, cause you wont see a batch of springs made by 5 different vendors.
Are those 2 different springs spec'd at those pressures, at the same installed height?

 

[87LtdT]

Agreed agreed. Spec for 980's was 91 lbs at 1.700"...however sometime in the recent past (5 years ago) the spec had changed from 85 lbs at 1.700" according to Comp Cams. 979 spec was 80 at 1.700". I obtained more dimensional detail on the 980...free spring length, wire diameter and spring OD. No surprise that the 80lb 980 was also the longest free length. Wire diameter was .177" for each....at least within the +/-.001 range in which I could accurately measure (digital calipers).

At the time I had an ex-coworker friend who had left and went to work for Peterson Spring...who made CC979, 980 and 981's at the time. He advised that the 979's would be a stock for stock replacement, 980's a mild upgrade, and 981's for a serious racer who didn't mind changing camshafts ocassionally. He also advised the 980 and 981 were made from a better wire material that took heat treatment better.

I'm confident in my measurement data and when talking (arguing actually) with Scooter and others at Comp Cams it was pretty clear to me that they seldom, if ever, measured the springs that they received. He offered to swap me the 979's for 981's a considerably more expensive spring.

I had 16 springs to choose from so I through out the extremes and ended up with 12 tightly bunched springs albeit at 75.5 lbs at 1.700" and 197 lbs at 1.25"...spring rate calculated to 269 lb/in versus the advertised 307 (interestingly the advertised rate of the 979's was 267).

Still have the data if you guys want to see it.

Bob