silent running

STi 3/4 heads. Following an essential recut of valve seats plus a fairly hefty 0.3mm skim of the heads, as suspected, the valve clearances are very small - far too small for my shims to be any good as they are (range 2.3-2.6mm). I tested one inlet valve setup which is fairly representative of all of them to give some 'ballpark' information:

• Cam lobe-to-tappet clearance (no shim) 1.25mm
• Cam lobe-to-shim clearance (no tappet) 2.05mm
• Test shim thickness 2.29mm
• Tappet thickness = 0.8mm (2.05-1.25?)
• Specified target clearance of 0.20mm => 1.05mm shim!

So I've got 30 or so normal range shims in the mid 2mm sizes, and I've got a set of valves that are going to want more like 1mm for this to work. I can see two options - either take roughly 1.5mm off the end of each stem; or get a load of much thinner shims made up.

Any pros or cons with one or the other method? Is the shim sitting on the retainer, or on the end of the stem (I'm wondering whether shortening the stems by a mm or two might not actually make any difference and leave the shim sitting on the retainer?)

Help!

silent running

bttt

172sport

iTrader: (6)

If you go that thin will they not break under use? I thought there was a min thickness.
I guess you have had new seats cut then? giving you the clearence issues.

If it where mine I would be tempted to take some of the valve and split the difference between that and the shim.

172sport

iTrader: (6)

You dont want it sitting on the retainer IMHO.

silent running

I'm going to shorten the valves. I've been through and measured all the clearances without shims and they're between 0.95mm and 1.50mm. There seems enough left protruding through the retainer to seat the shims properly on the stem ends, even if I take a couple of mm off them.