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robertcosta

Valve shims

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Hi all,

OK .... Rebuilt head on engine, leak down tests perfect on all cylinders...measuring the valve clearances I'm getting silly numbers like .3 on the intakes and .4 on exhausts..not all but you get the idea. I'm trying to workout why so big? Too much Loctite 518 and it didn't squish down? Replacement valve have shorter stems? Although the valves don't leak, maybe they weren't ground in as far as they should?

 

I'm going pull the towers off and refit them dry and see if it makes a difference.

 

Any thoughts welcome :-)

 

Rob

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What were your measurements before you applied the sealant? I'd be surprised if the Loctite 518 is to blame as it is meant to give a fitted clearance of  0.0005" and excessive application results in it squeezing out.

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Hi,

 

I recently rebuild my head .

I reused all valves after cleaning and grinding the seats. I spend 1 day checking and getting all the valve clearances within spec with the camtowers fitted dry.

All valves and shims were numbered, so I could install them exactly in the same place as I measured them

Afterwards I have used loctite 518 and the clearances stayed within spec, so I don't think dry or installed with the loctite 518 will make the difference.

In my opinion, if you used replacement valves, you should measure the clearances and reshim when needed, before installing with the loctite.

 

 

 

 

IMG_20140928_194243_zps0e8a51f1.jpg

Edited by gvy

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All I can say is when measuring for the required shims dont go by what the shims have stamped on them. I spent a whole day fiddling about and discovered that the shims themselves even though new were not what they claimed. So measure the shim thickness yourself . And, presumably you are not refitting the old shims they obviously will be out.

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Thanks for the responses :-)

I must confess to reusing the old shims in their original locations and not dry fitting prior to the measurement check...I 'spose its only cost me some Loctite 518..

I'm assuming you fit the old shims, check the gap, measure the old shim and order a new one with the old thickness + or - the measured gap, and this is the thickness of the new required shim?

R.

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Yes, that's it, the new shim is the old shim +/- the gap difference to the required clearance. Be prepared to go though the procedure a few times before you get the clearances to within specification. It's tricky to measure accurately and you'll almost certainly end up ordering more shims than you need to get it right.

Edited by sailorbob

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Infact, there is nothing wrong with the old shims, IF they give you the right valve clearance in the first place.

However,be carefull,the used shims can have a "pit" in the middle on the side where the valve stem pushes. So when you measure them with a calliper, make sure you measure it good.

 

In the end, you have to make sure that the chosen combination valve and shim (new or reused) give you the right clearance. If you are planning to use loctite 518 , you can testmount dry, measure with feeler gauges , try again until within tollerance , number and remount with loctite518.

 

Geert

Edited by gvy

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