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Shim measurement formula


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Hi guys,

How do I work out the new sized shims I need for the valve springs? I've just replaced the exhaust valves (inlets were fine) and measured the old shims so hopefully some can be reused.

Cheers,

Pete

Pete '79 S2

LEW Miss September 2009

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Pete it isnt all that difficult as I can do them :lol:

First you need some clearance between the bucket and the camshaft heel, so if you cant get any of your feeler gaugues in , substitute a smaller shim till y0u get some clearance.

Once you have clearance its just simple addition and subtraction. :)

Say you have .015" clearance on the exhaust tappet (too wide ) to get it to the reccomended .010"/.012" you will need to add .003" to .005" to your shim size required.

If the clearances are too tight, say you have .002" clearance (too tight) you will need to subtract .008" to .0010" off the shim measurment to get the correct size required.

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Thanks Wayne,

So I might as well put the old shims back in to do the measuring as long as I know what size they are already. What happens if I haven't got a small enough shim to give any clearance with the new valves?

Pete

Pete '79 S2

LEW Miss September 2009

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Thanks Wayne,

So I might as well put the old shims back in to do the measuring as long as I know what size they are already. What happens if I haven't got a small enough shim to give any clearance with the new valves?

Pete

<{POST_SNAPBACK}>

When I used to have the Hillman Imp (100 years ago) I once was stuck and ground a shim down using lapping paste and a piece of glass :lol:

But I would advise buying a few smaller ones for a kick off :)

XJ40 ones work (I get mine from a friend that specialises in Jags) :)

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When I used to have the Hillman Imp (100 years ago) I once was stuck and ground a shim down using lapping paste and a piece of glass :blink:

I did that too when I had an Imp. I remember when a piston got a hole in it and pressurised the sump as I was geting onto the motorway. Fired the oil filler cap off into the engine cover plus smoke. Sounded like a bomb had gone off. <_<

Anyway, the shims. When I did mine last year I found the car had been fitted with a gasket under the cam carrier. Wrong for this model. So had to make allowance for deleting gasket and adding loctite. Best way is to make up a small spreadsheet.

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