Valves are vertically aligned with the cylinder bore, Technically the vertical positioning imparts a direct force on the valve so there is no "Bending" moment.
IF you smash a lifter with enough force, by hand, the valve will not bend, but the possible outcome may be a damaged lifter.
Inside each lifter is a hydraulic channel with a check valve to trap oil and a spring. The spring is always trying to expand the lifter and allow for a chamber that oil can fill to take up the excess lash.
To check for damage:
- Use a plastic wedge
- Slide the wedge between the lifter and the cam
- There should be approx .5mm of compression on the lifter.
- The lifter must return to the contact position where it is in contact with the cam lobe on its own.
If you remove the lifters, and there is contact damage, you will see spider cracking on the upper face of the lifter. In some cases you may see a circular raised region identifying which lifter took an excessive impact.
Now, there is NO WAY a HUMAN can impart enough force to CRUSH a lifter (notice I did not say impossible) but lets not get caught up in semantics. If I find an engine out of time (Cam and Crank) by more than 7 degrees, all lifters get close scrutiny...
If you have a cam out for any reason, Compressing the internal plunger of the lifter and feeling the spring return the plunger to the extended position is a great check for lifter function. This requires compressing and squeezing out the trapped oil. Once the oil is expelled the spring and will be free to compress by force of your fore finger and thumb on the lifter body.
IF a valve is damaged, this is indicated by a jammed valve. Valves don't "bend" they compress. The shaft of the valve itself widens and jams in the valve guide.
IF you suspect a damaged head:
- Remove the cam
- Remove the lifters
- Inspect each lifter as described above, note any visual raised circular patterns in the center of the face
- By hand depress each valve and note any dragging of the valve on compression or return.
- IF you note any dragging, you have a compressed valve and this will require replacement before being returned to service.
- When you remove a valve, mic'ing each valve stem for diameter is a great way to identify valves that may have been struck by the piston(s). Any valve that has excessive shaft distortion must be replaced since it will have internal stress that will lead to eventual failure.
- Any valve that is found to be compressed, should also lead to a close inspection of the guide and or replacement of the guide and its seal. There is nothing worse than replacing a valve and installing it in a loose guide...
If a valve is "bent" the valve was crushed to the point that the shaft was no longer able to slide in the guide, now you more than likely have damage that is so severe that the entire head will require replacement...
