Valve springs are one of the most critical components of your engine. It is very important to match the camshaft and it's potential RPM range with the correct spring rate. We will attempt to explain it in this article, but first lets go over some valve spring terminology.
Free Height - is the overall height of the spring in an unloaded condition, when the spring is sitting on the workbench. |
Solid Height - is the overall height of the spring in a fully compressed condition, when every coil is touching an adjacent coils, above and below. |
Installed Height - is the overall height of the spring in a loaded condition, when the spring is installed on the cylinder head. |
Coil Bind - is the difference between installed height and solid height. The rule of thumb is, the maximum valve lift should never exceed the Coil Bind minus 10 percent, or a minimum of .050 (fifty thousands). |
Open Height - is the overall height of an installed spring, when the valve is in a fully open position. |
Seat/Closed Pressure - is the specified load on a spring, when the valve is in a fully closed position, measured in lbs per square inch. |
Nose/Open Pressure - is the specified load on a spring, when the valve is in a fully open position, measured in lbs per square inch. Note - the spring should be replaced if the pressure is less than 10% of the advertised Open Pressure. |
Spring Rate - is the amount of weight required to compress the spring by one inch, rated in lbs/sq.in. (not to be confused with Spring Rating - see below). |
Spring Rating - specifies load when fully closed (Seat Pressure) and fully open (Nose Pressure), may be a range or a specific number. Example: 80-85/160-165 or 80/160. |
Selecting Your Valve Springs |
Wives Tale: Too much spring pressure is hard on valves – In truth, what’s hard on valves is the speed at which they contact the valve seat when closing. What dictates how hard the valve hits the seat? It’s supposed to be the camshaft closing ramp (shape of the cam lobe), but when the spring pressures are too low, the valve does not follow it’s intended path and instead slams into the seat and actually bounces. Hence higher spring pressures can actually aid the valve by forcing it to more closely follow the shape of the cam lobe. On the other hand, to much pressure adds power robbing friction. It also increases the wear and tear on valve spring components. IE; broken rocker arms and valve springs, bent pushrods, worn valve guides, and so on. Therefore it is important to match the spring pressure to the profile of the camshaft. However you also need to take into consideration the intended RPM range of the motor. Basically...... faster ramp speeds (more lift for a given duration), and/or higher rpm's, require increased spring pressures.
Stock springs float around 4500 rpm, on a stock cam, so it's pretty obvious they won't work with a performance camshaft. Back in the good ole days, shade tree mechanics simply installed a handful of shims under the valve springs to increase pressure, but this lead to a host of other problems, which usually resulted in valve train failure. It's much better to use a stiffer spring to avoid any possibility of coil bind. Small Block Ford (SBF) V8 valve springs (289/302/302HP) work well on stock and/or mild performance cams. Or you can use a single spring with a damper to reduce damaging harmonics in the valve train. The only drawback to using dampers, is that they usually require machining the valve spring seat. Dual springs are used for high performance cams and/or cams that frequently see high rpm's, such as a race motor. On the other hand, softer spring pressures can be used to reduce wear and tear on the valve train components, providing rpm ranges rarely exceed 4500-5000rpm.
When installing a new camshaft or valve springs, always check and verify the installed height, seat pressure, nose pressure, coil bind, retainer to rocker arm clearance, and retainer to valve seal clearance. Failure to do so may result in severe engine damage, and voids all camshaft and/or spring warranties. |
Classic Inlines offers high quality springs manufactured by Clay Smith Cams and SI Valves. We only sell valve springs that are made from the finest silicone and/or stainless steel wire, which are precision wound, shot-peen'd, detailed, and heat-treated, to precise tolerances.
Stock Replacement Springs (single) are intended as a replacement spring for stock, low lift OEM cam profiles only, as well as low rpm ranges which will not exceed 4500 rpm.
302/302-HP Single Springs are perfectly suited to engines using a mild performance cam, however special care must be observed when installing these springs, as it is very important to verify all valve spring clearances whenever new springs are installed, paying particular attention to the installed height and coil bind. To archive adequate pressures with a single spring, manufacturers need to use a thicker wire, which reduces the clearance between the coils, possible creating issue with coil bind. However if the springs are installed properly and the clearances are carefully checked and verified, you should be OK. Many engine builders prefer to use a single spring due to their ease of installation, as single springs with a damper, and dual springs, normally require additional machine work to the spring seats, or the use of custom spring cups.
If you plan to use high ratio rocker arms, you need to pay close attention to coil bind. High ratio rocker arms increase total valve lift, which can easily exceed the capabilities of a single spring, especially those with higher pressures (thicker wire), such as the 302-HP springs. In most cases, Classic Inlines recommends the use of single springs with a damper, or dual springs, whenever high ratio rocker arms are used (see charts below).
Single Springs with Dampers: These springs are recommended for higher revving engines, using a performance camshaft with higher lifts, and/or whenever high ratio rocker arms are used. The benefits of a single spring with a damper are substantial. First and foremost, the damper reduces harmonic vibrations in the valve train components, there-by reducing valve train wear and/or component failure. They also offer increased safety in the event of a broken valve spring, as well as increased spring pressures, to eliminate valve float at high RPM's, while reducing coil bind issues in high lift applications.
Dual Springs: Dual springs are recommended for higher revving engines, with medium to high lift camshafts, and/or whenever high ratio rocker arms are used. Like the single springs with a damper, they reduce harmonic vibrations in the valve train components, there-by reducing valve train wear and/or component failure. Dual springs increase safety in the event of a broken valve spring. They also offer even higher spring pressures, which eliminate valve float at high RPM's, while reducing coil bind issues in high lift applications.
Beehive or Conical Springs:
Retainers & Locks: They are a wide variety of valve spring retainers, available from a wide variety of suppliers, however Classic Inlines is one of the few places where you'll find a 5/16" one-piece retainer in stock. Our light-weight high-performance retainers are manufactured from the highest quality materials, to the industry's most exacting tolerances. And there's no need to worry about selecting the right retainer for your application, as our custom retainers fit all of the springs we sell. Sold in a pack of twelve retainers, and twelve locks (7°).
Valve Spring Cups: Classic Inlines recommends the use of spring cups, or locators, on all cylinder heads. They not only protect the head and shim, they also locate and align the spring. Maintaining correct spring alignment, ensures spring longevity, while reducing wear on the valve stem and guide. Unfortunately we don't carry them at the present time, but we plan to manufacture a custom cup in the near future.
| Classic Inlines Spring Specifications |
Part # / App |
Description |
Seat
Pressure |
Open
Pressure |
Coil
Bind |
Recommend
Cam Range |
Comments |
SSI-OEM-SPG
170/200/250ci |
Single Spring |
54 lbs |
150 lbs |
.430 |
Stock only |
Recommend
289 valve springs |
SSI-289-SPG 170/200/250ci |
|
|
|
.530 |
|
verify coil bind
and clearance
|
SSI-302-SPG
170/200/250ci |
|
|
|
|
|
Verify coil bind
and clearance
|
SSI-302-SPG-HP
170/200/250ci |
|
|
|
|
|
Verify coil bind
and clearance
|
CSC-200-SST
170/200/250ci |
Single Spring
w/Damper |
80 lbs |
170 lbs |
.925 |
up to 265 Dur. |
Viton Seals & Machining may be Required |
CSC-200-STY
170/200/250ci |
Single Spring
w/Damper |
100 lbs |
180 lbs |
.925 |
up to 275 Dur. |
Viton Seals & Machining may be Required |
CSC-200-TOY
170/200/250ci |
Dual Spring |
110 lbs |
260 lbs |
.925 |
up to 295 Dur. |
Viton Seals & Machining may be Required |
Spring Application Chart |
Spring |
Application |
SSI-200-SPG |
Stock springs should only be used on stock motors, which are intended for show only or occasional street use, that will never be rev'd over 4500 rpm. |
|
Stock 289 SBF springs are a great upgrade for stock motors used as daily drivers, but rarely rev over 5000 rpm. |
|
Stock 302 SBF springs are an excellent choice for stock or mild performance motors with our 264/274 camshafts. They are used for daily drivers or weekend cruisers which occasionally rev to 5500 rpm (6000 rpm maximum). |
CSC-200-SST |
These springs (with dampers) are a great upgrade for stock motors used as daily drivers, but rarely rev over 5000 rpm. While they are very similar to the 289 springs above, they include a damper to reduce damaging valve train harmonics. |
CSC-200-STY |
These springs (with dampers) are an excellent choice for stock or mild performance motors with our 264/274 vans. They are similar to the 302 springs above, however they include a damper to reduce damaging valve train harmonics. Rev range is 5000-5500rpm (6000 rpm maximum). |
CSC-200-TOY |
These dual springs are intended for performance motors with cams in the 260-280 range, which frequently see higher rpm ranges, up to 6500rpm. Dual springs increase open pressure to prevent valve float at higher rpm's, yet maintain an acceptable seat pressure, reduced friction and cam wear. |
Note: Installation of our single springs with dampers, and/or dual springs, may require machining to eliminate the cylinder head valve step on a stock cast iron cylinder head, which was intended to keep the stock single springs in correct alignment.
Note: To install .500 Viton seals, a valve cutter must be used to machine the valve guides, this helps to keep the seals securely seated on the guides once installed (.530 seals do not require machining). The .500 Viton seals are recommended when using dual springs, such as our CSC-200-TOY, as they increase the clearance between the seal and inner spring.
Machined valve guide |
Viton Seals .500/.530 |
Here's a chart to help you select the proper springs for your application and rpm range.
Cam Profile |
Intended Application - RPM Range
|
Show Car
max 4500 rpm |
Daily Driver
4500-5000 rpm |
Mild Street
5000-5500 rpm |
Strip/Street
5500-6000 rpm |
Strip Only
6000+ rpm |
Stock Cam |
Stock |
289-SST |
289-SST |
302-STY |
302-STY |
264/264 |
289-SST |
289-SST |
302-STY |
302-STY |
TOY |
264/274 |
289-SST |
289-SST |
302-STY |
302-STY |
TOY |
274/274 |
289-SST |
302-STY |
302-STY |
TOY |
TOY |
278/278 |
302-STY |
302-STY |
TOY |
TOY |
|
280/280 |
302-STY |
302-STY |
TOY |
TOY |
|
294/294 |
302-STY |
TOY |
TOY |
|
|
In the charts below, we used the 302 and 302-HP valve springs, along with our H264 camshaft, on both the cast iron and aluminum cylinder heads, to determine if these springs would work with high ratio rocker arms. And if so, which ones?
Note: these charts are currently under construction 4-2-2011
| Cast Iron Cylinder Head |
|
Installed
Height |
Solid
Height |
Coil
Bind |
Max
Valve
Lift
|
Camshaft
Lobe Lift |
Rocker
Ratio |
Actual
Valve Lift |
Difference
(max-actual) |
Acceptable |
302 |
1.680 |
1.100 |
0.580 |
0.522 |
0.320 |
1.5 |
0.480 |
|
|
302 |
1.680 |
1.100 |
0.580 |
0.522 |
0.320 |
1.6 |
0.512 |
|
|
302 |
1.680 |
1.100 |
0.580 |
0.522 |
0.320 |
1.65 |
0.528 |
|
|
302HP |
1.680 |
|
|
|
0.320 |
1.5 |
0.480 |
|
|
302HP |
1.680 |
|
|
|
0.320 |
1.65 |
0.512 |
|
|
302HP |
1.680 |
|
|
|
0.320 |
1.65 |
0.528 |
|
|
| Aluminum Cylinder Head |
|
Installed
Height |
Solid
Height |
Coil
Bind |
Max
Valve
Lift
|
Camshaft
Lobe Lift |
Rocker
Ratio |
Actual
Valve Lift |
Difference |
Acceptable |
302 |
1.600 |
1.100 |
0.580 |
0.522 |
0.320 |
1.5 |
0.480 |
|
|
302 |
1.600 |
1.100 |
0.580 |
0.522 |
0.320 |
1.6 |
0.512 |
|
|
302 |
1.600 |
1.100 |
0.580 |
0.522 |
0.320 |
1.65 |
0.528 |
|
|
302HP |
1.600 |
|
|
|
0.320 |
1.5 |
0.480 |
|
|
302HP |
1.600 |
|
|
|
0.320 |
1.6 |
0.512 |
|
|
302HP |
1.600 |
|
|
|
0.320 |
1.65 |
0.528 |
|
|
  
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