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post #1 of 3 (permalink) Old 03-05-2017, 06:22 PM Thread Starter
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advice on measuring valve shims

I am replacing the stock cams in a 2L with a set of Shankle 5417 cams I purchased years ago. The motor also has a Wes Ingram Modified Spica pump. I removed the stock cams and installed the new ones. (The base on the new lobes measured aprox .5mm smaller than the stock cam so I knew I would be ok using the stock shims to get my measurement for the new shims.) The measurements of the shims in the motor don't equal what is available. Shims should be on .025mm increments. Some are real close i.e.. 2.049 etc so I assume that would be 2.050 but a few measure quite off. i.e. 2.141, 1.960, 2.070

Here's my question, in doing my calculations should I round up/down on the shim measurement that is in the motor to the closest .025 and then add the gap measured or do I use the actual measurement. In some cases it doesn't matter because either way it falls within the range of one shim, but in two cases the difference from actual thickness to the closest .025 results in calling for the next thickness. I know I can just purchase a few extra shims to cover the range but I'm curious if this is common or I am I not being accurate with my tools. I's a digital micrometer, I re-zero it often and it accurate to .001mm when checked against my feeler gauge. I cleaned the shims to remove any crud. I really just want to do this once. Oh, and one shim has some scuff marks but none look they have been ground down.

JEBoniface
83 GTV-6 3.0L
79 Alfetta
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post #2 of 3 (permalink) Old 03-05-2017, 06:36 PM
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Quote:
The measurements of the shims in the motor don't equal what is available. Shims should be on .025mm increments. Some are real close i.e.. 2.049 etc so I assume that would be 2.050 but a few measure quite off. i.e. 2.141, 1.960, 2.070
Yes, that's the way it is; there is nothing wrong with your measuring. While the shims are supposed to fall into exact .025 mm increments, they just don't. And to add to the confusion, sometimes the suppliers get their stock mixed up and you will receive a shim that is a whole .025 mm off. The bottom line is that if you think you need a 2.050 mm shim, it is best to order a 2.025, 2.050, and 2.075. It is really nice to have a large assortment of shims when you do this job.

Quote:
in doing my calculations should I round up/down on the shim measurement that is in the motor to the closest .025 and then add the gap measured or do I use the actual measurement.
Definitely the actual measurement.

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I really just want to do this once.
Sorry, it just isn't that simple.

Jay Mackro
San Juan Capistrano, CA

'65 Guilia Sprint GT
'67 Duetto
'91 164L

Last edited by Alfajay; 03-05-2017 at 06:45 PM.
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post #3 of 3 (permalink) Old 03-05-2017, 06:44 PM Thread Starter
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@Alfajay - That's what I was thinking. With all the Alfa projects I've done over the years this is the first time for this particular job so I was looking for some reassurance. I'll go with the actual and not the "supposed to be" thickness.

JEBoniface
83 GTV-6 3.0L
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