Need valve spring pressure specs

[VeesGN]

I bought a set of comp 980 springs and the machine shop wants to know the pressure specs. What do I tell him--stock or?

 

[Intercooler]

Not to bash him but he should know this. It all depends on what you go by. GN-1's use 1.727" installed height and I used 1.700" installed height. As for the springs he should have a pull tester to show what they are rated at when set to the stock height. HTH

 

[VeesGN]

I'm sure he knows the stock specs, but I threw him a curve by giving him comp springs. He also showed me 2 different specs for "stock" also. I don't remember the exact numbers, but I think they varied between 80-90lbs +/- 4. Would the comp springs use the same specs or would they end up slightly stiffer?

 

[Intercooler]

It all depends but usually the 979's and up will have more pressure. I used 1.700" to get my LT-1's at 100 lb. seat pressure. Say you had 979's you could install them at 1.725" and get 80 lbs. If you go to 1.700" it should increase it to 85 lbs. Only thing you have to be carefull of is coil-bind so at full lift .450"-.470" you have to make sure the springs aren't stacked and have clearance between coils. Depending on the cam 85 lbs. should be plenty.

 

[ijames]

Go to http://www.compcams.com/catalog/304_305.html for the full story, but they give seat loads (it's a load or force, not a pressure ) of 91 lbs at 1.700 inches and 229 lbs at 1.250 inches, with coil bind at 1.150 inches and a spring rate of 308 lb/inch. That should be enough to make your machinst happy .