valve spring advise

[turbocamino1]

Yes...true in a general sense but we aren't talking about massive differences...and spring breakage in our application is a rare event so wouldn't worry about that.

The force exerted by the springs when compressed to 1.25" was:
979: 174-184 lbs with standard deviation of 2.40 lb (16 pcs)...throw out the single 174 spring and the range was 179-184 w/std dev of 1.71
980: 193-199 with st dev of 1.56 (16 pcs)...throw out the single 193 and range was 195-199 w/ std dev of 1.2
LT1: 240-253 (12 pcs) w/std dev of 3.77
Original Stock: 170-180 (12 pcs) w/std dev 3.12

Standard deviation is a measure of variation within a group of parts...the bigger the number the larger the variation...so the smaller the number the better. It is a key indicator of a manufacturers ability to produce the same part over and over.

Interesting to see that the 35k mile stock springs had a lower std dev than the brand new "LT1s" which were obviously a low quality spring and very doubtful a genuine GM spring.

By the time I threw out 4 of the 980 springs I installed 12 that had a range of 196-199 w/std dev of 1.19.

I noticed this all took place in Aug-Sep of 2000.

Bob

Outstanding info....thanks very much for everyone's input!

 

[streetknight]

Years ago, Red Armstrong told me the cup was a dampner and to eliminate it or remove the ones from the new springs, but not to run both. This is the way I've always done it. But that was "years" ago lol

 

[87LtdT]

I have a lot of respect for Red and agree that the cup could act as a dampner on the bottom end of the spring...but see no harm in using both the cup and the flat coil dampner wound inside the 980's and presumably the 981's.

Eliminating the cup changes the spring force (aka seat pressure). You take the thickness of the cup (about .030") times the spring rate of the spring (307 lb/in for the 980) and multiply them together to get about 9 lbs difference in spring force if you eliminate the cup...you lose this 9 lbs when the spring is compressed as the cam lobe goes over the top too.

So if you are wanting a stiffer spring than the 980 and go to the 981 I definitely would not use the cup...but I would use it with the 980's.

Bob

 

[87GN_70GS]

now,it seems there are 2 concerns...too much seat pressure and overall consistant quality. I can locate a spring tester, but i would like to only go through this once. if comps are inconsistant like i have read...and this is from someone in our community you all trust very much...(D.B.) he has personally tested box after box and now wont use comp springs. so...draw your own conclusion. I see Sealed Power makes a series for our cars; VS677 and VS1615 but i dont know the breakdown on the seat pressure or heights.

VS677 and VS744 are stock-type replacements, they will have stock force numbers.

 

[streetknight]

I have a lot of respect for Red and agree that the cup could act as a dampner on the bottom end of the spring...but see no harm in using both the cup and the flat coil dampner wound inside the 980's and presumably the 981's.

Eliminating the cup changes the spring force (aka seat pressure). You take the thickness of the cup (about .030") times the spring rate of the spring (307 lb/in for the 980) and multiply them together to get about 9 lbs difference in spring force if you eliminate the cup...you lose this 9 lbs when the spring is compressed as the cam lobe goes over the top too.

So if you are wanting a stiffer spring than the 980 and go to the 981 I definitely would not use the cup...but I would use it with the 980's.

Bob

Just occurred to me. Red told me to use the 980 spring with no cup, since the replacement spring was a 979 which wasn't made anymore. doing away with the cup, would make it as close as possible to the same pressure as a 979 with a cup.

Anyways, I just ordered some 980's for the car I'm working on as its a daily driver. So cups or no cups, that's the question lol?

May try the cups this go around.

 

[87GN_70GS]

Just occurred to me. Red told me to use the 980 spring with no cup, since the replacement spring was a 979 which wasn't made anymore. doing away with the cup, would make it as close as possible to the same pressure as a 979 with a cup.

Anyways, I just ordered some 980's for the car I'm working on as its a daily driver. So cups or no cups, that's the question lol?

May try the cups this go around.

The cup is a dampener. If the new springs come with an internal dampener
(they are single springs, not dual springs, any inner "spring" will be a flat-wound dampener) then you won't need the cup.

 

[85HOT-T]

Call Mike Litch and ask him to get you some PAC-1215's. 105# on the seat and you know they are the best springs availible and also made in the USA.:smile:

 

[turbocamino1]

Update...i did buy 16 980's and all but 2 where ok...they fell below the others by 2Lbs. Installed yesterday. > quote" Call Mike Litch and ask him to get you some PAC-1215's. 105# on the seat and you know they are the best springs availible and also made in the USA" Great..now you tell me

 

[85HOT-T]

Update...i did buy 16 980's and all but 2 where ok...they fell below the others by 2Lbs. Installed yesterday. > quote" Call Mike Litch and ask him to get you some PAC-1215's. 105# on the seat and you know they are the best springs availible and also made in the USA" Great..now you tell me

Sorry a day to late buck too short lol. At least you know for next time.

 

[bogies87]

So what was the final outcome......did you install with the cup or no cup?

 

[ttaowner]

did the car run any better after the spring swap????