valve shims
10-09-2011, 02:28 AM
#2
Three Wheelin'
For a solid follower setup:
Too thick of ship will prevent valve from fully seating. This also opens the door to overheating the valves, since heat will not be removed through the seat contact. Symptoms will probably be the same as a bent valve. I suppose there is the possibility of damaging the cam and follower since the pressure wave will partially be acting on the cam to follower contact point, instead of the valve seat.
In extreme cases, the valve can be open far enough to strike the piston.
Too thin of a shim will not provide full valve motion. Also there's the possibility to damage the cam and follower since the contact will be made further into the cam profile than intended. Since the ramp will be steeper, at this point, the cam will essentially slap the follower and valve open.
Too thick of ship will prevent valve from fully seating. This also opens the door to overheating the valves, since heat will not be removed through the seat contact. Symptoms will probably be the same as a bent valve. I suppose there is the possibility of damaging the cam and follower since the pressure wave will partially be acting on the cam to follower contact point, instead of the valve seat.
In extreme cases, the valve can be open far enough to strike the piston.
Too thin of a shim will not provide full valve motion. Also there's the possibility to damage the cam and follower since the contact will be made further into the cam profile than intended. Since the ramp will be steeper, at this point, the cam will essentially slap the follower and valve open.
10-09-2011, 01:25 PM
#5
Rennlist Member
your machine shop should be handling all of this, spring pressure and install height. I take the head to the shop and and pick it up in a plastic bag ready for installation.
10-09-2011, 04:06 PM
#7
Race Car
You should be shunning for seat and open pressure (mostly seat)
The way it works is you check the recommended installed height, check the valve spring to make sure it is within tolerance, check your distance between retainer and head, shim to get proper distance. Also check coil bind height to make sure the springs won't bind (generally only on high performance applications)
I have added shims to add a little seat and open pressure but I triple check coil bind height and leave .100 extra.
The way it works is you check the recommended installed height, check the valve spring to make sure it is within tolerance, check your distance between retainer and head, shim to get proper distance. Also check coil bind height to make sure the springs won't bind (generally only on high performance applications)
I have added shims to add a little seat and open pressure but I triple check coil bind height and leave .100 extra.
