Valve spring shims

When you do a valve job which requires "tipping" the valves (valve grind, seat re-cut etc) it is recommended to fit shims under the valve springs to maintain spring pressure (thanks zed1015) I have found these shims 15.8x32x0.76mm intended for classic "air cooled" VW/Porsche cars. They are not expensive at just under $20 for a set of eight (might be cheaper across the pond as they are an EMPI product from the US) available from classic VW outlets.

Thanks for posting that option.

In the past I have just walked into a automotive engine rebuild place and rummaged thru there odd shims spare bin with a vernier caliper. I have found that shims for Cadillac V8's fit KZ heads and they come in ranges from .010" to .030" and higher.

All I need to explain is that I was rebuilding a Kawasaki Z1 head and they were more than happy to help out. The V8 builder's had no issue selling on spare shims for coffee money as a fist full of shims cost me $5.

Nick Pepper at SPS in Norfolk has APE ones.
They £9.95 per set of eight + post.
 

How does one determine the appropriate thickness, assuming shims may be needed?

Schumann took care of that when APE springs were installed with a new set of valves...

🙂

 

daveo wrote:

How does one determine the appropriate thickness, assuming shims may be needed?

Schumann took care of that when APE springs were installed with a new set of valves...

🙂



 

Shims are needed when sinking the valves or tipping the stems substantially.
Your are ok tipping the valves by the factory 0.3mm figure but much over that you then really need to shim the springs by around the same amount especially if using all the engines performance where the valves may float as the rpms increase.
So in the case of tipping the valves collets and retainers by 1mm you would then need 1mm shim to restore the springs original installed height and pressure.
Also in the case of aftermarket springs or cams there may be a specific seat pressure figure required to control valve float and shims would be needed to achieve this.
You would use a spring pressure gauge whilst compressing the spring to the required installed height and then add shims until the target pressure at that height is reached.

The BUGPAK items I bought are 0.76mm which should be fine as the seats and valves only needed a light cut to take the "pitting" out. I checked out the APE ones from SPS that zed1015 suggested, (on their website at least) they had 0.36mm and 1.5mm which I don't think would have been right for me. I'm kinda happy to be honest, as a "cheap Wookie" I would have been inconsolable if I had paid more than I needed to - Lol

Wookie58 wrote:

The BUGPAK items I bought are 0.76mm which should be fine as the seats and valves only needed a light cut to take the "pitting" out. I checked out the APE ones from SPS that zed1015 suggested, (on their website at least) they had 0.36mm and 1.5mm which I don't think would have been right for me. I'm kinda happy to be honest, as a "cheap Wookie" I would have been inconsolable if I had paid more than I needed to - Lol

Here today, gone tomorrow...
Gotta grab while it's available!

🤔

I took my exhaust valves where 2 had 2.00 shims, got some 1/4" shaft collars and drilled them out to 9/32" or about .006 over size to the valve stems.  I then assembled the valve with the retainer and collars with the shaft collars holding them together and my local head machinist put them in his valve tip grinder and we ground off .010" of the assembly.  Very quick and easy.  For shims McMaster Carr an online hardware store has both metric and inch shims, a pack of 25  1mm shims is about $12.  also in .5 and thinner thicknesses.  I didn't install them as I have APE springs and don't really push the motor that hard often.

When I shimmed the APE springs for my 1200cc head I had to make some shims out of .005" copper shim stock.

Out of the box the springs ranged from 78 to 86 PSI at installed height after cycling in a vice to coil bind a dozen times. I was able to set the intake side at 82 PSI and the exhaust side at 88 PSI by using .005" and .010" shims. After break in the there will still be adequate spring pressure as those numbers will drop by at least 4 PSI or more. If I have to tear it apart someday I will remeasure to see where they settled at.