WTB Shim Under Bucket

[greenMachine]

Why are we talking about grinding the skirts of the shims? The skirts are necessary to keep the shim located on the end of the valve stem ...



PS: I speak as someone who has had a shim (unmodified skirt) come off the valve stem when a piece of FOD got caught between the valve head and seat.

PPS: You aren't putting the shim on the bucket's post?

PPPS: The only time I grind skirts is on the dancefloor ...

[manga_blue]

I had to have the skirts ground off mine because they would have fouled the collets otherwise. The SUBs I had meant the shims had to be mounted on the valve stems. After grinding skirts there was still plenty left for safety.

When mounting shims on valve stems you need to do your own measurements rather than going just on Chris's previous specs. NA and NB collets are different sizes and aftermarket valve springs usually come with their own retainers. So there are a few variables to factor in.

[greenMachine]

Ahhh, ok! Yes, shim-on-collet sounds like imminent bad news!

Thanks manga, learnt something today!

[GR124]

PPS: You aren't putting the shim on the bucket's post?

Yes, I'm now putting the shim on the bucket post/stem. I have read from a post direct from Emilio (949Racing/Supermiata) that he does it and asked Chris at Precision Shims in OZ just days ago and he said there is no issues. I can't see any.
I'd rather run a shim with a longer skirt on the bucket stem than a vary short one on the valve.

If you can see issues or heard of any let me know? I'm no expert

[greenMachine]

My comment was predicated on my use of gutted hydraulic buckets, where the post terminates as a flat disc, compared to the end of the valve stem where they are chamfered. If you buy shims for that style of post, they should fit cleanly and closely. I would hope that the internal space would have parallel walls all the way, as I recall my shims I think there is a shoulder at the base of the internal wall (or maybe the walls are tapered?), presumably sized to fit the valve head chamfer. I will have a look later today and report.

Regardless, providing Chris knows what you are doing with what, I'm sure his advice would be solid.

[GR124]

All good GreenMachine, A little misunderstanding.
Just to clarify for people following. The Buckets I have for the SUB set up have a machined internal stem it measures 5.56 diameter and is machined parallel down the stem 3.5mm to small step.
precision shims recommended I use the 5.6mm ID x 3mm skirt and 8.5mm OD

[The American]

I received an email from the engine builder asking me to order another set of 8x 1mm shims.

I asked him if these were still for measurements only and this was his response:

It worked out that I could get the shim & bucket setup close enough when cutting the seats to the oversize valves, now I will be able to trim a little off the stem end to set the clearance.

This is using Maruha lifters and Supertech valves/springs.

[greenMachine]

Whatever works, I suppose ...

Not the way I would do it, but then I don't earn my living doing this sort of thing. I'd enquire about case hardening of the tip, and the effect of grinding. If the shims are sitting on the tip (as opposed to sitting on the bucket post), there needs to be a chamfer to mate with the shim's lip. My other concern would be subsequent adjustability, but as long as there is enough meat in the shim to allow sufficient future grinding it should be ok - if you need thicker shim(s) later, they can be ordered to suit. But you don't want to have to remove and then totally dismantle the head just to re-do the valve clearances. The possibility of shim/collet interference should also be closed out as he would be bringing the shim closer to the collet.

But if he 'always does it this way' he probably has all that covered off.