Valve spring/retainer question

[Michael C.]

Re: Valve spring/retainer question

The retainers must fit tightly to the springs, and the locks (keys/keepers) must be compatible with the retainers. Generally, for stock or mildly modified (hot street/mild race) 7 degree keys/retainers are used. 10 degree keys/retainers are used with more exotic setups. Finally, both of these items must be matched to the OD of your valve stems, which is 11/32". If you are using stock replacement springs, like VS-677, then they should be installed at 1.7" height (valve closed). There are keepers/retainers available that can allow extra installed height when using a standard length valve stem, without any additional machining of the spring pockets................ I bring up all of this, just to show you how many variations of each component are possible. It is wise that you verify each item, and install only compatible components. Any mismatch is sure fire disaster!

For your application, valve springs need not have any higher rate than stock because the mild, gentle cam you are using does not require it. Of primary concern is to use a light weight spring which provides no more force than is necessary both on the seat or over the nose. Too much seat force causes excessive seat recession, insufficient force causes power robbing seat bounce. Excessive over the nose force causes pulled valve spring studs, worn lifters and cam lobes, insufficient force causes valve lofting. Additionally, excessive spring force causes excessive heat.

Pulled valve spring studs are a very real possibility if you use springs that are less compliant than the original or stock replacements. Spring pressure @ installed height of 1.70" should be about 80 pounds, @ 1.25" it should be about 200 pounds. Spring rate for your springs is 267 pounds/inch with coil bind @ 1.15", which gives you a SAFE max valve lift of .450" (using a .100" safety margin).

Here is a video of a valve spring system at high speed. Now imagine the result of a loose fitting spring retainer:

http://www.youtube.com/watch?v=_REQ1PUM0rY

I am about to install some VS677 springs on my 72 LT-1. The engine was rebuilt in 1985, and I do not know exactly what components were installed then. My issue is the installed height of the springs. Right now my retainer to spring seat measurment is 1.915" (from the bottom of the retainer). My springs measure close to 2.000" I assume this means the builder deepened the valve seats, or put longer valve stems in? The springs that were on the car looked like stock (2.0" long)... but only giving about 50-60# pressure at 1.7".

There were .0625 shims on the seats, but even with those installed, it won't get me that close to the 1.70" recommended installed height for the VS 677. If I count the spring cap (.030) and the .0625 shim, then I can get the measurement down to 1.8225". Is it advisable to add MORE than one shim on the bottom of the spring to fill up the gap? If not, will I need to get a stiffer spring to provide the needed seat pressure at that 1.8225" height?

Thanks,

Mike

[Clem Z.]

Re: Valve spring/retainer question

I am about to install some VS677 springs on my 72 LT-1. The engine was rebuilt in 1985, and I do not know exactly what components were installed then. My issue is the installed height of the springs. Right now my retainer to spring seat measurment is 1.915" (from the bottom of the retainer). My springs measure close to 2.000" I assume this means the builder deepened the valve seats, or put longer valve stems in? The springs that were on the car looked like stock (2.0" long)... but only giving about 50-60# pressure at 1.7".

There were .0625 shims on the seats, but even with those installed, it won't get me that close to the 1.70" recommended installed height for the VS 677. If I count the spring cap (.030) and the .0625 shim, then I can get the measurement down to 1.8225". Is it advisable to add MORE than one shim on the bottom of the spring to fill up the gap? If not, will I need to get a stiffer spring to provide the needed seat pressure at that 1.8225" height?

Thanks,

Mike

yes you can use more than one shim but use the combination of the thickest that will work and if you have to use a thin one put it on the bottom not next to the spring.