Minimum thickness of the tappet

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Mich7920
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#1 Minimum thickness of the tappet

Post by Mich7920 » Wed Jan 09, 2019 9:06 am

Hi all,
To have the good clearance on two exhaust valves I need to use a tappet in 0.0835 and one in 0.0845.
The minimum size we find is 0.085 and of course I 'm going to make the one I need but is there a problem using these extra small size ?
Mich
Michel
1963 E Type OTS - Angus Restoration
1965 E Type FHC - Front Restoration

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christopher storey
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#2 Re: Minimum thickness of the tappet

Post by christopher storey » Wed Jan 09, 2019 11:38 am

Michel : provided that the shim is still sitting above the valve spring cap there should be no problem. The only danger arises when the shim is so thin that the tappet is actually pressing on the valve spring cap rather than on the shim.( There is then a danger of releasing the collets ). I should use silver steel for the shim unless you have your own hardening process/capability

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Mich7920
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#3 Re: Minimum thickness of the tappet

Post by Mich7920 » Wed Jan 09, 2019 12:35 pm

Thanks Christopher, I understand and didn't want to lose the valves!
I use old Shims for the new one.
The side with the old trace of the valve is machinning and place against the cap.
The intact side is against the valve.
Michel
1963 E Type OTS - Angus Restoration
1965 E Type FHC - Front Restoration

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christopher storey
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#4 Re: Minimum thickness of the tappet

Post by christopher storey » Fri Jan 11, 2019 3:03 pm

Michel : have you actually tried to machine an existing shim? My experience has been that they are incredibly hard and will take the edge immediately of any tool used. The only effective method to thin them in my experience is to grind them, but doing this accurately is very nearly impossible. This is why if you want to make your own replacement , a hard metal such as silver steel is best. Even then, how long they last is hard to predict

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Mich7920
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#5 Re: Minimum thickness of the tappet

Post by Mich7920 » Fri Jan 11, 2019 4:12 pm

Christopher,
I recovered my old/new shims this morning from the professionnel who machined them.
He is a sharpening specialist.
I Gave him two old original and one newly buy.
I think he work with diamond grinding wheel on a very special machine.
The one newly buy was 2.85mm and I needed 2.82mm. He did the job correctly.
It's closes so I can't tell you more.
Mich
Michel
1963 E Type OTS - Angus Restoration
1965 E Type FHC - Front Restoration

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