Measuring valve spring installed height

[GSX_Dan]

I just purchased the FP dual valve springs and they need to be shimmed for the FP3x cams I got to 1.475"-1.485". I've never had to shim valve springs before so I'm not sure what measuring tool I need to use on our heads and exactly how you would measure (from what point to what point). I'd like to do this myself rather than pay a machine shop for work that I enjoy doing, and it's a reason to buy a new tool

 

[groundPork]

The way I have always done it, is to have a spacer made of aluminum that looks like a sleeve. It takes the place of the springs them selves and is exactly 1.000" tall. The installed height is anywhere from .200-.400" taller than that, so you measure the rest of the travel with either a dial indicator, or a dial caliper(if you have a fixture to hold it square. Add the two and that's your installed height for the outer main coil. if there is an inner subtract the inner step height if applicable and the spring retainer step, and make an appropriate stack of shims that will fit inside the main coil to simulate them. I find some carefully chosen pennies usually do the trick. of course the real problem is measureing the acutal pressure it produces at the installed height. I have seen cheap mini scales sold by some engine builder tool supply places like Goodson tools, and jegs. it's simple may not be the most acurrate but good enough with practice. a lot cheaper than the official $800.00 unit!!! Shimming will only help if you still have enough room before coil bind (where the coils all touch) if it doesn't you'll wear out or break other valvetrain parts. also the closer a coil opperates to coil bind, although not binding, the more likely you are to fatigue the metal and evetualy bring on a failure. also be sure if you shim, shim only under the spring seat, not directly under the spring itself. And check all of this, obviously, before installing any of your brand new seals! Oh, and don't stack shims, or shim so much that the seat is brought to the top of the heads couterbored locating area, it could move out of the locator... that is unless it located off of the guide... take from .001"-.010" play to locate safely. This keeps the springs from rubbing near by stationaly parts, and helps keep the tendancy of any spring to surge, and "dance around".

Hope this helps you. if you are serious and would like further recommendations on tool sources, let me know. Ultimately I would have to recommend going with a pro on this one though, as they can quickly and easily readjust machien work, if necessary to get the right numbers.

I figure anywhere from 75-87 psi on the seat closed, and about 170-186 over the nose is ideal pressures, but some applications require more, usually not less. in case you were wondering. And although i do liek my titanium spring retainers, i don't really feel they are always necassary.

Good luck engine building!

I just purchased the FP dual valve springs and they need to be shimmed for the FP3x cams I got to 1.475"-1.485". I've never had to shim valve springs before so I'm not sure what measuring tool I need to use on our heads and exactly how you would measure (from what point to what point). I'd like to do this myself rather than pay a machine shop for work that I enjoy doing, and it's a reason to buy a new tool