Shim thickness under Valve Springs??

[Chris McDade]

Does anyone know how thick the shims should be that go under the valve springs?? I have .015( 15 thousandths ) in there now and they are chewed up. My head guy wants to put .030 in there. Is this to thick? My seat spring presure is 120lbs with the .015. It will be around 130-135lbs with the .030. Is this ok for a hydraulic comp cam 218/218. I just want to make sure that I don't have to much seat presure and wipe out a cam lope.

Thanks in advance

 

[gofstbuick]

I alsways thought the spring shim was used to get the correct installed height. If the spring is installed at the correct height, than the closed pressure matches the spring spec closed pressure. Example, my springs are 110#@1.7inches installed height. I use a 0.025 in the one of the spring pockets to acheive 1.7 inches, I may use 0.010 in another spring pocket, to acheive the 1.7 inches installed height. As a result, all my valve springs have the same installed height and all the close pressures match for each valve.

 

[Chris McDade]

gofstbuick,
I am by no means a head expert here ... You are probalby right. I will check with my head guy and see if he is measuring the spring height by the shims.

thanks

Anyone else out there

 

[Nick Micale]

For a hydraulic roller cam 130-135#'s would be ok.

We stay between 100-110#'s for flat tappet and have had no problems.

What spring pressures does Comp state for your cam?

 

[Chris McDade]

Hey Nick,
I called comp cams and they told me seat spring presure is 80lbs at 1.770 valve height. That seems kind of light to me. They also told me 200lbs open @1.250 valve height. That also seems kind of light. Anyone else running a comp hydraulic flat tappet 218/218? What are your springs ratings?

My head guy told me that the seat presure closed would be around #125-130 when finished. Is this to much? He also told me that the open presure would be around 270lbs. It this much?

Thanks in advance

 

[gofstbuick]

Chris,
I would follow what Nick says, IMHO 125-130# is a little too heavy.

 

[gofstbuick]

Also, I hope your machinist isn't shortening the spring travel less than 1.77 inches installed height to acheive these close pressure numbers. That IMHO would make things even worse and may cause coil bind.

 

[Chris McDade]

gofstbuick,
Thanks I think you right. I will call my head and tell him to keep it around 110lbs.

Thanks

 

[gofstbuick]

Out of curiosity, what is the installed height of the springs you're running, what is the open pressure, and at how many inches (or fraction therof) does coil bind occur. How does that compare to a stock spring or a comp cam 980 spring or the recommended spring for the cam? These are the kinds of dimensions you want to compare when selecting a valve spring. If you get coil bind sooner that with any of the recommended springs (for your cam), think of what that will do to your valve train.