After adjusting the valve lifters on a '20 block a friend observed that a couple of the lifters did not rotate (while the engine running) as all of the others did. As this seems like it could affect wear (or even be the result of wear) I wonder if anyone can offer advice. Is this an issue or not?
I may be mistaken, but I don't believe that Model T cams are ground with tapered lobes that later cams came with to facilitate lifter rotation.
The lifters have, or are supposed to have, a slightly convex surface. Shouldn't that rotate them?
I don't think any real effort was made to make the lifters in a model T rotate, but they often do. A little wear, uneven hardening, or even a harmonic vibration, could cause an individual lifter to rotate, or not. There is no reason that one could not do so if they wanted to. However, I have never heard of anyone doing so that I can recall.
Id be curious if the T lifter truly does have a convex shape to the bottom like more modern engines. If they do, that should cause them to rotate.
In a more modern engines, especially with higher spring pressures and the lack of zinc in certain oils, a lifter on a flat tappet cam that doesn't rotate is almost certain death to that particular lobe and possibly the rest of the engine due to the pressurized oil system passing the debris through the engine.
A little OT, When I assemble V-8's for muscle car era vehicles, and when running flat tappet cams, I mark the lifters and set them in the block with cam. Even hand cranking with a breaker bar on the front of the crank will cause them to rotate, and I can see that by my mark on the lifters. Sometimes one or two will stick, standard procedure is to swap a couple around. If one lifter bore is still sticking, some times a light hone is all that is needed. I have seen a stuck lifter take out brand new engines doe to the fine metal grit passing through the pressurized oil system and tearing up the bearings, and scuffing pistons and walls. Filters don't always catch everything.
Steve, I believe that the lifter faces are flat (or supposed to be). See this post of Herm on "butt grinding" lifter faces:
Thanks everyone, If I summarize correctly, the lifters may or may not rotate. It is good if they do (more even wear) but not to worry if they don't.
I hope I got this right.