Thread: are shims under valve springs necessary?

just got my head back from machine shop. they installed bc 1mm over valves springs and retainers.when i got it back and some extra parts i supplied i noticed they did not install all the shims under the springs. i gave them 16 and i got 12 back. i know they set the spring heights so i am assuming the shims were not needed. but the shims are all the same size so they are more of a spacer than a shim.anyone have any experience or input on this

If the machine shop was to re-shim it they'd need the entire valve train. Cams, caps, HLAs, rockers. They are completely necessary. Without them as soon as you try to crank all the rockers will fall out of place. Shims also go on top of the valves inside the hole in the center of the retainer, not under them. They support the rockers, and, if properly installed, take up the slack between the contact surfaces of the cam lobes, rockers, and valves while the cam lobes are at zero lift. Normally each one will have slight variations, so most shims will all be somewhat different thicknesses. Can't remember what it's called, but there is a base shim (specific thickness) that you start with, then check each one with a feeler gauge. After that you would add/subtract and install the proper size shim on each one. There is only one shim per cylinder. The slotted ones are to keep the rocker centered, and in place. All of this info I just typed is good, but if you have HLAs, and not solid lifters, then you can just install them and go. The HLAs are self adjusting, and should take up the slack that might be there. Solid lifters have to be dead on though, as there's no play to them. It's always best practice to put everything back in the same order, but you should be ok here. So one shim and slotted puck per cyl then. You will need to source some more man.

Edit; also there is a how to with pics on cam install including re-shimming somewhere.

yes i understand everything you are saying. but under the valve springs there is a washer type shim/spacer which is what i am concerned about.i am using solid adjustable lash adjusters that will adjust the rocker to cam clearences which is not done yet.

The shims are for doing seat pressure more than anything and compressed height. The springs have a rating on what the spring height is supposed to be when the valve is closed. Thats all the shims are for. So if they used some and not others then they probably did a correct job in measuring the spring height installed. When i pulled apart a couple heads not all the springs had shims under them. Setting the spring height installed is all that matters. So as long as thats correct, I wouldnt worry about it.

i kind of did not think it was a issue. just want to be sure before messing up a head i put alot of time and money into.

Oh, yeah. I forgot about those damn things, lol. I had no idea they were there for actual shimming of the spring height. All of the heads I've taken apart had them under all springs. When I installed my BC springs I left them as is.

I also imagine they are for seats to keep the metal springs off the actual aluminum of the head as well. But they are also for spring installed height as well.

That's what I always thought.

they should be under all springs. so the spring doesn't dig into the aluminuim.