Shim shenanigans!

[Thunderroad]

Hi all,

Was wondering if i could have some opinions on this?

I am currently doing the valve clearances on my cerb and have ordered some new shims of various sizes (from a reputable supplier) that came today.

I am just a bit concerned obout four of them, (the thicker ones) as they have a small concave indentation on the inner surface of the shim which i assume has been left from the manufacturing process.

Is this normal? My thinking is that they will have less surface area in contact with the valve end, which will in turn expose that shim and the valve end to a higher load, higher load = more wear.

1. Am i just being over cautious? And is this normal?
2. Or should i not use them and speak to the supplier?
Many thanks.

[GT6k]

I don't think i would be concerned. I found the opposite problem with some of them having a dimple in the middle which I had to grind off. I need some thick ones who is your supplier ?

[portzi]

GT6k said:

I don't think i would be concerned. I found the opposite problem with some of them having a dimple in the middle which I had to grind off. I need some thick ones who is your supplier ?

The engineer has just gone a Little deeper on some of the shims that's all whilst removing the pip in the middle, left there from the machining process.

[Thunderroad]

Thanks for your comments, Gt6 - i have e-mailed you.

I spoke with the supplier this morning and they have given them the all clear and also offered to send out another batch if i am still concerned. A good response in my opinion.

I told them not to bother with the replacements as they won't get used as these need to go in today so i can progress onto the other bank, and get to Cerbfest next weekend

Simon.

[Thunderroad]

O.k. Well, it all went back together ok and i managed to make it to Cerbfest
And then to Germany and back so i'm feeling pretty good with myself right now.
So i thought i would round it all up with an update as i can see that "tappet adjustment seems to be a popular topic at the moment.

When i inspected the shims on the second head i was a bit disappointed to find that a couple of the shims when removed turned out to have the same issue that some of my new shims had (as discussed earlier in this thread) and as i suspected, this does damage the top end of the valve stem due to point loading!


This then gave rise to another problem, i needed to change this shim, and the new one to be fitted, did not have the imperfection that the one i was replacing did. I would now get "point loading" again! Due to the valve end being deformed by the imperfect shim.

I decided to remove the nipple on the end of the valve with a dremel, i peirced a latex glove and and stretched it over the end of the valve so it fitted tightly over the valve end just above the collet. And then layed out some rags to cover the rest of the exposed valves and got to work.

This did the job, and allowed me to fit the new shim correctly onto the valve stem.
The car has since done nearly 2000 mile and seems to be fine but i will pop the rocker covers off again in the winter and measure the gaps, i expect the two i had to grind down will now have beaded in so the gap may be out again.

There seem to be a few of these imperfect shims around, i would say don't use them unless you have no choice, i broke my golden rule of not giving myself deadlines. When carrying out jobs such as this, it just puts you under pressure and you corner yourself into doing things you would not normally do. (In this case, using imperfect shims).

And just for the record, i didn't have a special tool to clamp the cam shaft sprockets, i just used cable ties to clamp the chain to the sprocket and a long cable tie around a bit of wood wedged down the side of the engine to keep a bit of tension in the chains.
And also, a grinder disc removal tool is very handy, (as it fits into the bolt holes at end of the camshaft where the sprockets would normally be) to turn the camshaft to check the clearances after adjustment (engine in the safe position).

Simon.

[ukkid35]

The concave indent represents less than 10% of the total surface area, and yet the force is great enough to distort the top of the valve stem?

Seems unbelievable, suggests that the valve stem isn't hardened at all. I'm not an engineer or a metallurgist but I'm struggling to get my head round that.

Thanks for sharing the photos!

[Bogsye]

Here's my progress. Having realised the raise tip on the valve stem was causing issues, I have also gently relieved the high spot.
The issue it caused for me was that I'd checked the initial gap, and figured the appropriate thickness shim.

On putting in the 'new' shim I then had a smaller than desired clearance. The reason for this was the new shim didn't have a recess on it's underside, so the shim sat high on the valve. The shim obviously wouldn't sit nicely either which was undesirable. The point load would have been in issue.

I had two valves with this issue - here's an inlet
IMG_1463

My spare shims - Bit of an assortment
IMG_1470

No.6 looks a bit iffy - I'll swap this one out
IMG_1469

Here it is masked
IMG_1472

So, for future orders of shims, I'll be specifying I do not want any significant reliefs on the underside,

Just the other bank to do now.....

Cheers,
Brian

Edited by Bogsye on Tuesday 29th August 20:34