I bought a 124" power package from S&S to rebuild my 107" 2018 SGS.
The package includes the 0.605" Heavy Duty Valve Springs intended to be used with S&S 550 camshaft.
Because I want more low end torque I have decided to install the Cyclerama 480 MT camshaft.
I have understood that any camshaft up to 0.485" lift can be used with the stock valve springs.
Nevertheless, I would like to use the included 0.605" valve springs, as the cylinder heads and springs are already disassembled and completely cleaned.
I have carried out all the measurements according to S&S instructions: they are all within the specs (Installed spring height is between 1.535" and 1.540" on all of the valves).
In addition, I have measured all the components ( Valve springs, Top collars, Keepers, Seals/ Bottom collars) for both stock and S&S .605" Valve Kit, they have an identical length.
When I carry out the necessary calculations, I get the following results for the valve springs:
Stock S&S .605" S&S .605"
Target installed height: 1.535" 1.535" 1.535"
Cam lift: - 550" S&S 550 - 0.480" CR 480 MT
Free Travel: 0.985" 1.055"
There would be a difference of 0.070" in Free Travel between the 550 cam and the 480 cam.
The big question is: Can I install the 0.605" springs and go with the Cyclerama 480 cam without using shims to compensate the difference of 0.070" travel or is there any danger of valve floating???
And if shims are necessary, what size should they be ???
I couldn`t find a table or other information to answer this question......
Thanks!!!
When testing cams, I used high lift springs without shims, because the range of cams I wanted to test ran from .46" lift to .52". Little danger of valve float with most of these cams, as they make peak power below 5600.
The note about installing at higher spring height inducing valve float has to do with sunken valves, and valve stem protrusion height. If you sink the valves, and do not shim to correct for seat pressure from the greater installed height, you won't have enough spring pressure to control the valve properly. If your installed height is correct, and your springs are OK, spring pressure will be adequate.