Digital micrometers for valve clearance adjustment...

[foler]

I need to buy digital micrometer for valve adjustment. I saw some cheap on ebay:

http://www.ebay.com/itm/0-25mm-0-001mm-LCD-Electro...

http://www.ebay.com/itm/Digital-Outside-Micrometer...

Is this two have enough accuracy for job?

[kev b]

A high degree of accuracy is not needed for this job as the shims are only available in certain sizes and are not always exactly the same as marked anyway.

Any micrometer will be way more accurate than the feeler gauge used to measure valve clearance, you just need to replace the existing shim with one which will achieve a gap in the correct range.

Used shims often are worn in the centre as well meaning the shim will not give the gap you expect if you use it on a different valve or fit it the other way up.

Edited by kev b on Sunday 27th January 13:54

[E30M3SE]

As above, replacement shims are made to 2 decimal places.

[DVandrews]

I shim cams all day long and often grind the shims to thickness, an inexpensive set of digital calipers is more than accurate enough , far easier to wield and a lot less expensive. I have digital micrometers going from 25mm to 200mm but never use them when measuring shims.

Dave

[foler]

but shim is thinner in center than at edge. Digital caliper measure at edge, micrometer in center. Why is caliper better?

[DVandrews]

Maybe the shims you use are different in design to the ones I use which are basic pellet type shims, circular and of uniform thickness, a caliper is much much faster to use.

Dave

[foler]

Shim is the same but I think that shim is wider that cam lobe. So cam "grind" shim only in the middle region.

[kev b]

Some engines have their shims under the bucket, bearing directly onto the valve stem, this type are more likely to develop a depression in the centre of one side of the shim. If this shim is swapped to another valve then it must be measured in the centre with a micrometer and fitted the same way up.

I know you should ideally use brand new shims but they are not always quickly available and can be pretty costly especially for motorcycles so it is expedient to swap them about, this caused me a deal of head scratching when I first tackled shimmed valves.

I was loaned a big box of shims for my Lotus Twin Cam, some of them were dimpled, others were marked incorrectly and some had been ground but retained the original markings,this gave me hours of cheap entertainment until the penny dropped.

Off topic, if you really want a challenge, try shimming Ducati valves with the engine in the frame, I would rather tackle a V12 and would probably do it in half the time.

[foler]

Yea, having shims all sizes will be great...Good is that shim can be used from volvo 240 and fiat, 33mm in diameter and cost 1/5 bmw price. Maybe I will find some set here.