seat : 140lbs

open: 390lbs

install : 1.800

coil bind: 1.07

1.290 O.D.

max lift : .660

matl : super pure chrome silicone

- PRC Platinum springs:

seat: 145# @ 1.7850"

open: 395# @ ?

PP, PRC, TEA, and all other "Gold" springs are all made from the same manufacture; Associated Springs. The differences are in the retainers and seat locators.

7. Comp 977's: dual spring (requires machining of spring pockets)

O.D: 1.46

I.D: .700

seat pressure: 155 @ 1.850

open presure: 419 @ 1.250

coil bind: 1.195

spring rate: 441

8. Comp 978's: Dual springs (requires machining of spring pockets)

O.D: 1.46

I.D: .697

seat pressure: 126 @ 1.850

open presure: 368 @ 1.250

coil bind: 1.195

spring rate: 403

9. Comp 987's: Dual Springs (require maching of spring pockets)

O.D: 1.430

I.D: .697

seat pressure: 121 @ 1.800

open presure: 388 @ 1.200

coil bind: 1.150

spring rate: 344

10. 01 LS6 springs: max lift .540

O.D:

I.D:

seat pressure: 90 @ 1.800

open pressure 260 @ ?

11. 02 LS6 springs or green: max lift ~.580

O.D

I.D:

seat pressure: 90 @ 1.800

open pressure: 294 @ ?

12. 03+ LS6 springs(orange): max lift ~.580

O.D

I.D:

seat pressure: 90 @ 1.800

open pressure: 294 @ ?

13. Stock Ls1 Springs

O.D:

I.D:

seat pressure: 75 @ 1.800

open pressure: 230 @ ?

Valve Springs: Frequently asked questions

from CraneCams website





What is Valve Spring Installed Height?

Installed height (also called assembled height) is the dimension measured from the bottom of the outer edge of the valve spring retainer where the outer valve spring locates, to the spring pocket in the cylinder head, when the valve is closed.



How does installed Height affect spring tension?

Installed height is the determining factor of what the valve spring "closed tension" or "seat pressure" will be. The camshaft specification card, and the spring section of the catalog both show what the approximate tension a particular valve spring will exert if installed at a specific height.

For example, spring part number 99848 shows 114 lbs. @ 1.700". This means that if this spring is installed at a height of 1.700" it should exert 114 lbs. of tension with the valve closed. (Note: Spring tensions often vary measurably within the same production runs; therefore, it is recommended that each spring be tested on an accurate spring tester and the spring installed at the recommended seat pressure.)

How do you change installed height and what effect does it have?

The easiest way to shorten installed height is to insert a shim in the spring pocket below the valve spring. Another is to use a different design valve spring retainer. Retainers with a deeper dish will have more installed height, with a shallower dish, less installed height. You can also use a valve lock designed to change the location where the retainer is positioned on the valve stem. We sell heavy-duty, machined valve locks in std. height and also +.050 and -.050 heights to fine tune your installation. Longer length valves can be used to increase installed height.







The shorter the installed height (the more the spring is compressed), the higher the valve spring seat pressure will be, and the less distance the spring can travel before the spring reaches coil bind.

The taller the installed height, the lower the valve spring seat pressure will be, and the further the spring can travel before coil bind occurs.

(Note: Eliminating coil bind by installing the spring at a taller installed height is not a desirable option. The resulting reduced seat pressure will lead to a significant loss in performance and could also result in engine damage caused by the valve bouncing on the valve seat due to the reduced seat pressure. The best procedure is to select a spring that provides the desired seat pressure at the installed height on the head.)

What is the importance of valve spring seat pressure?

Adequate seat pressure is necessary to:

1) Insure tight contact between the valve face and the valve seat to seal the combustion chamber and provide proper heat transfer from the valve to the cylinder head.

2) Keep the valve from bouncing on its return to the seat. If the valve bounces, cylinder pressure (power) is lost. Repeated bouncing of the valve is like a hammering action that can result in the head of the valve deforming ("tuliping") or actually breaking from the valve stem resulting in catastrophic engine failure.

3) With a hydraulic cam the valve spring must exert enough pressure against the valve lifter (or lash adjuster) plunger to keep it centered in its travel to prevent "lifter pump-up". When pump-up occurs the valve is held slightly off its seat resulting in a significant loss of power and possibly a misfire. It is this loss of power and misfire that is often misdiagnosed as a fuel system or ignition system problem.

High oil pressures and high viscosity oils aggravate "lifter pump-up" in hydraulic lifters. When either oil pressure or oil viscosity is going to be increased beyond the manufacturer's recommendation, a corresponding increase in spring seat pressure is necessary to prevent "pump-up" (even with an "anti-pump-up" lifter). Since oil viscosity in no way relates to the oil's film strength, and the scuffing protection provided by the film strength, Crane Cams recommends following the OE manufacturer's recommendation with respect to engine oil.

Common Misconception:

Many people mistakenly think that using higher seat pressures causes a reduction in the horsepower delivered to the flywheel because higher seat pressures (and also higher spring rates required for high performance) require horsepower to compress the springs. This thinking is simply incomplete! For every valve that is opening and its valve spring being compressed, another valve is closing and its valve spring is expanding. This expansion returns the energy to the valve train and the engine. This results in a net power loss of "0" hp. Many engineering texts refer to this as the "regenerative characteristic" of the valve train. Recent tests at Crane have shown no horsepower loss on a hydraulic roller equipped engine when changing the seat pressure from 135# to 165#. Power actually improved significantly at top end, probably due to better control of the relatively heavy valves in the engine.

In Summary: