Pictures - up pipe and valve spring cups

[mblum]

Yes, those shims will work with the stock cylinder heads.

1.250" OD X .814" ID X what ever thickness you decide to use.

 

[Fikse7]

I did Comp 980 springs without cups and I used shims that brought them to 1.697" seated. Your shooting for 1.7" so you can get the spring pressure up to its listed seat pressure of 92 at 1.7". Can't remember exactly but I wanna say I used .030 shims under the springs or else the springs are 1.667" installed by themselves and the pressure is way lower than rated. I think it drops down to the like 84psi at 1.667" rather than 92 pounds seated pressure at 1.7". Its best to buy a set for 8 cylinders and have a shop pressure match a 6 cylinder set for you. That is all I can say to that.

Joe,

Trying to understand this in my simple mind, but wouldn't the height be greater without the shims? Without the .030 shims, it would be 1.697 + .030 = 1.727??
Am I understanding this correctly? Also, using shims for reduced installed height = more seat pressure?

 

[pacecarta]

no it will be shorter , installed spring height decreases with the shim
with 030 the 1.697 will now be 1.667 and spring pressure will increase because you've raised the floor squeezing the spring
shimming also changes (reduces) the amount of travel the spring has before bind . should not be an issue with stock cam lift

 

[Fikse7]

no it will be shorter , installed spring height decreases with the shim
with 030 the 1.697 will now be 1.667 and spring pressure will increase because you've raised the floor squeezing the spring
shimming also changes (reduces) the amount of travel the spring has before bind . should not be an issue with stock cam lift

Got it - thank you

I've ordered the CC shims so I can install each spring at 1.70 height. Assume shims are placed directly on top on the head, nothing extra required to keep them in place?

 

[mblum]

Correct,

They sandwich between the spring pocket in the cylinder head and the spring itself.

I would suggest getting a valve spring micrometer, this way you can at least check the height. You wouldn't have any way to check pressure, but at least you know the height and ensure they are all the same from one valve to the next.

Something like this:

Proform Parts 66902 Proform Valve Spring Height Micrometers | Summit Racing

Free Shipping - Proform Valve Spring Height Micrometers with qualifying orders of $109. Shop Valve Spring Height Micrometers at Summit Racing.

www.summitracing.com

 

[XracerX]

OOPs. I explained that all wrong didn't I.....
I accidentally did the math backwards.

I found that the Comp Cam 980's would be about 10#'s or so less on the spring pressure at 1.727", which would be the installed height without the stock spring cups. Stock valve spring installed height with the cups(0.040" height) is 1.687". Now in order to bring the spring to it advertised specs I had to shim them with an 0.030" shim which brought them down from 1.727" to 1.697".