Valve shimming

[DobroDog]

@ 30,000 miles the valves needed shimming on my Tiger. What parts are wearing down that make shimming necessary?

Thanks

DobroDog

[Mustang]

2 things cause it

1. the valves are actually pounding themselves deeper and deeper into the valve seats
(on a pushrod type engine , not overhead cam , they would get looser . On a overhead cam engine like tiger they get tighter )

2. the the valve face is actually starting to mushroom away from the stem which will let the valve stem come higher into the head thus reducing clearance .

sorta like whats happened to this woman's umbrella

[DobroDog]

2 things cause it

1. the valves are actually pounding themselves deeper and deeper into the valve seats
(on a pushrod type engine , not overhead cam , they would get looser . On a overhead cam engine like tiger they get tighter )

2. the the valve face is actually starting to mushroom away from the stem which will let the valve stem come higher into the head thus reducing clearance .

sorta like whats happened to this woman's umbrella

Thanks Mustang, clear enough for even me to understand.

DobroDog

[ChazzyB]

1. the valves are actually pounding themselves deeper and deeper into the valve seats
(on a pushrod type engine , not overhead cam , they would get looser . On a overhead cam engine like tiger they get tighter )

Au contraire, clearances will close up on a pushrod engine too, if the valve head is burying itself in its seat. Wear anywhere else in the valve train will see gaps getting larger, so just the same as an OHC engine.

[cosmo]

On a flattie, they will tighten up. Might be what he was thinking.

Causes burnt valves.

Cosmo