School Me On Valve Spring Shimming

[bugguy1967]

Can someone school me on valve spring shimming? I searched before posting using "valve spring shimming" and got some info, but not enough. I don't want to learn how to do it; just how to instruct my machinist on what I want/need so I get exactly what I have in mind. I need to know if any factors, such as cam profile, brand and style of spring, weight of valves, pushrods, lifters, rocker arms, and retainers dictate different install heights. Are there charts online, or links to articles that have the information i need?

When I purchased my CB springs, they told me an install height, which I wrote down and put inside the baggy that my valves came in. I think it was .150", but can't be certain. Is that a general safe setting, or should I take that to the bank? I just want my heads set up properly the first time.

Btw, all my valvetrain parts, aside from my rocker arms are lighter than standard HP parts (titanium retainers, lighter than standard SS valves (weighed them against others) aluminum HD pushrods, Ultralight 28mm lifters). If that will change anything, I'd like to know.

[modok]

First you need to know valve lift, and coil bind, and work your way back from there.

If you want to get the most out of springs, run .070"-.090" from bind.
So we put a spring on the tester and find bind. Wright that down.
Now go bind plus .080", measure pressure, this is your over the nose pressure.
Now bind plus .080, plus valve lift, measure pressure, that is your seat pressure.

With that wrote down you can decide if you want to run looser(less pressure), and how much. Most springs are linear, so you know pressure at two heights then you can calculate pressure at any height.

Usually, general purpose installed height is 1.500 or 1.550, that is probably what CB meant. Is that ideal???? maybe, but probably not.

When you have your installed height figured out, grind a coathanger, or piece of 1/8 welding rod, to your desired height. Put the heads together without springs and hold that thing in there and see how many shims you can fit between the rod and retainer.

IMO, this is the easy way, and works on any engine.

If they are dual springs, you can measure them separately, or at the same time using the retainer, then subtract the thickness of the retainer.

[mark tucker]

if your machinest doent know......you might want find another one .or have him find out so it dosent get lostin transulation.

[RHough]

[bugguy1967]

Of course I know what kind of springs I purchased. I'll talk to my machinist then. I don't have any working spring testing equipment, so I guess I'll let him deal with it. I say working because I have an old Rimac spring tester that needs to be sent in for a rebuild.

[RHough]

[Type 5 Joe]

There isn't much to a Rimac spring tester...They have a chunk of leaf spring in them.
They have different ranges of spring pressures for different models... Make sure your tester is in the appropriate range for the springs your testing.

All you need is a calibration spring (purchase from Rimac).

They also sell other replacement parts if needed.... I have restored a few over the years.