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Discussion Starter #1 (Edited)
I bought these used shims back in 2008 and took them out today to record their measurements for a valve lash adjustment that will be starting soon. Seller said that a number of them have been ground down and that there were a number of stock sizes in the lot.

I will let the pictures describe what they look like but what I thought was strange was the shirts were different lengths and on some skirts there was manufacture groves or lines?

Is there any shims in the lot that are good?
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Hi Murray,

I measured the skirts on my spares. I only have 13 of them.

1 was the highest at 4.80mm
1 was the low at 4.60mm
The remaining came in between 4.72mm to 4.76mm

I am sure the real engine builders will chime in but if it were me, I would not use the shims that have been ground down.

Looks like you will have plenty to choose from.

Good luck,

Vin
 

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If you wish dispose, send them to me. Please.
 

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Like DPeterson3, I don't see the problem with them. As long as the two surfaces are parallel, grinding them isn't an issue. It is common to find grooves around the OD of these shims - not sure what the purpose or origin of these grooves is, but they don't cause any problems.
 

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I have ground quite a few shims over the years with no problems. I place the shim onto an old valve stem and contact the side of a bench grinding stone which is spinning at full speed. The shim spins on the valve stem as it is ground which keeps the surface flat and perpendicular.
 

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Now that we know the shims are good, I would like to learn why do builders grind down the skirts?

I understand why the faces are ground, that is to achieve a certain thickness to achieve a certain valve clearance.

Thank you for the learning opportunity.

Vin
 

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The single groove means they are the extra hardened shims for the V-6 intakes. They were twice the price of the regular shims. When Fiat took over they said the 4 cylinder ones were fine in the V-6's and discontinued them.
 

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So long as the interior and exterior faces are parallel they can be used. If not, then those shims can be ground parallel to a reduced size when required. In short, keep 'em...
 

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Now that we know the shims are good, I would like to learn why do builders grind down the skirts?
Quite easy. Valve collar clearance sometimes only is by 0.1mm which isn't enough. If you have to shorten the valve stem so you need to shorten the shim skirts, too. It's all about valve seat height, valve lenghts, cam base circle dia. when reground and collar clearance.
 

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Quite easy. Valve collar clearance sometimes only is by 0.1mm which isn't enough. If you have to shorten the valve stem so you need to shorten the shim skirts, too. It's all about valve seat height, valve lenghts, cam base circle dia. when reground and collar clearance.
Exactly!

Which is why I always suggest using a machinist who really understands Alfa heads. Here in the US, most automotive machine shops are familiar with pushrod V8's and will set Alfa valves so that no factory shim will do the job. Modifying shims is a work-around for that level of head machine work. The "small block Chevy" shops are fine for bottom end work, but invariably fail with heads.
 

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As mentioned, the shims with the groove are from the 6 cylinder cars, They are interchageable to the 4 cylinder cars. Also as mentioned, some machine shops will, after grinding the valve face (part of a "valve job") will grind away a similar amount off of the top of the valve stem (topping the valve). This is common practice when working on pushrod V8s. For our old Alfas, this is a no-no. What can happen is that the bottom of the shim "skirt" can (if too much of the top of the valve stem is removed) contact the top of the valve keepers. This can (at best) screw with your valve adjustment procedure, or (at worst) unlock your valve keepers and unleash a valve onto your piston. I always check my valve - keeper - shim clearance visually before I begin to assemble my heads. As for removing a little bit off the top, or skirts of a shim, I have a few pieces of double thick pane glass with different grade (adhesive) sand paper attached. I use my finger, rotate the shim every few strokes, and take my time. Never a problem in 40 years of building Alfa engines. As for using a grinding wheel, I hope that those who do, use the side of the wheel and not the face. The face cuts concave, not flat.
 

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I recently had our local NAPA do a head job on our '83 spider head, factory shims worked great and she runs great.

An experienced engine builder I am not, but personally I would not grind shims. It's possible they are surface hardened and maintaining parallel faces could be problematic. Just buy new ones
 

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An experienced engine builder I am not, but personally I would not grind shims. It's possible they are surface hardened and maintaining parallel faces could be problematic. Just buy new ones
The shims are through hardened and can be ground to adjust thickness with no problems ... 0.050 (1.25 mm) is my minimum. I don't like shortening the "skirt". If necessary, replace the valve seat.
 

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Discussion Starter #15 (Edited)
I recently had our local NAPA do a head job on our '83 spider head, factory shims worked great and she runs great.

An experienced engine builder I am not, but personally I would not grind shims. It's possible they are surface hardened and maintaining parallel faces could be problematic. Just buy new ones
Thanks 930cabman, you confirmed what I was thinking.

I am going to buy new ones, thought the same, do the grinded shims have "parallel faces"? I'm going to buy the needed shims that my math says I need, and one size on either side of it.

My shim collection will might climb into the mid twenties after this job. :)

The plan is to by a bench grinder and find someone to buy a junk valve from so I can be sure the faces are parallel.
 

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High performance cams often have different base circles than stock AR cams and shims collected from stock motors may not be of much help to you. In your case building up a collection in the range that your cams use is a good plan. In a few years time when you have to adjust them again a little grinding on your new collection may enable get on with the job without waiting for more new ones.
 

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High performance cams often have different base circles than stock AR cams and shims collected from stock motors may not be of much help to you. In your case building up a collection in the range that your cams use is a good plan.
Ed is exactly on the point.
When one is collecting shims from stock engines, 99 % of the collection will always be in the range of 2.25 to 1.95 mm thickness. Latest by 3rd or 4th adjustment of a valve on a non-rebuild head you're running into the 1.5mm range you can't serve any more with a standard collection then.

Engine builders do usually calculate shim thickness before the engine build to end up in a range of 2.75 to 2.25mm especially when using different cams.

Grinding off the skirt 0.3-0.5mm will not cause a problem. On used engines sometimes needed on 1 or 2 valves until full rebuild is needed.
 

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Discussion Starter #18 (Edited)
Ok, today I got the master link removed from the chain, pulled the intake cam, followers and measured the old shims.

Now I'm hung up with the math to figure out what sizes I should order. My common sense tells me that with my intake lash @ .006 and I want it to be .008, I need to subtract .002 from whatever the the old shim measurement is and that is the size of the shim I need to buy.

My logic is I don't have enough valve clearance (gap between the follower and bottom of the lobe) and I need a smaller shim to have more clearance.

Then I watch this video of how to check the valve lash on a 91 Alfa head and he gave the example of if you have a valve lash of .014 and you need .015 you need to add .001 to whatever the old shim measures that was in there. He was talking about lift saying for IE: .014 has .001 more lift the .015 so you need to add .001 to the old shim size, to determine the new shim that needs to replace it. Totally screw me up!

I have found posts on the Alfa BB search that backs up my way of thinking but I just want to be sure.

I have the lash record

I have the difference between the lash I have and the lash I need.

I have the size of the shim.

I'm just not sure if I should be adding or subtracting the difference between what i have to want I need to the old shim size, to find out what size of shim I should order.

I can't find any excel type program that I can check my math with, I tried the one on the way back site that have the Alfa engine but it does not calculate, same with another one they have the cells but will not calculate?

Any help would be most appreciated!
 
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