VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 216 Valve Lifters

I was in my local engine rebuilder's shop today discussing various issues in the rebuilding of my 1940 216 motor. The camshaft looks really nice except for a large chip out of the ramp face on the #4 exhaust cam lobe. The rebuilder said that could be repaired and the camshaft reground. Then he mentioned that the lifters should be re-conditioned at the same time. He said that the lifter faces originally had a slightly convex surface to aid in rotating them as they are lifted by the cam, and that these faces eventually wear and need to be reground. There is no mention of this in the 1940 Chev shop manual, and I've never heard of this before. Can anyone verify that the lifter faces on the 1940 216 engine were originally slightly convex?

Mark Yeamans
VCCA #35724

Mark, well, all I've ever seen do rotate. I suppose the reason is because the lifter is slightly convex. Otherwise, if the lifters were just plain flat, then the pushrods would just sit there having no means of rotation. So, having the top of the lifters slightly convex would make sense and explain the rotation.

I think that Gene will verify that the lifters are convex pretty soon. I just got up before him this morning is the only reason I answered first. I think maybe he likes to sleep in. (zzzzzzzz)
Charlie

Mark
Some manufacturers ground the valve lifters convex and some concave but both achieve the same result but I am not sure when this was started.
I would go with your rebuilders suggestion as he will probably be advised by the cam grinder as to the angle required.
Tony

I know that lifters in the '28 engines were ground slightly convex. All the lifters in later engines that I have worked on also had convex lifters.

What is the process for reparing the chip on the cam lobe? I was under the impression that you could by new cams these days.

Not really a bad problem. The cam will be welded up and then reground to original specifications.

I would not suggest removing any material from the lifters. The surface is hardened.
The lifters/push rods rotate because the run off-set on the camshaft lobe.
From the 1940 Features - the 1940 is the first to have the taller lifter. "The neww tappet is made in two parts to permit better control in manufacturing the seat, which is made of steel with a hardened , smoothly finished cup for the push rod.
When casting the shell, the cam face is treated to provide extreme hardness and afterwards is polished to a very smooth finish for contact with the hardenedn cam. The cams on the camshaft are treated chemically to cover them with a special coating for protection of their surfaces, especially during the break-in period as well as through out the entire life of the engine"

From the 1934

Features. "to insure rotation of the lifters in one direction, the cams are all off-set from the tappet center a greater amount "

I can find no reference to concave or convex lifter surfaces. My thoughts are the surface would need to be flat due to the fact the camis off-set from the center of the lifter.

I had the cam regound on my '34. This caused the adjusting screw in the rocker arm to go down very far and the lock nut would just catch a few threads.
Perhaps new lifters would be a better move. They fit 1940-1953 216 engines and are not too rare.

A good cam shop can and will grind lifters. The then harden both the cam lobes as well as the lifter bottoms. At least that is what those around here do.

I have installed NOS lifters in my 1940 216. All of the NOS GM 1940 lifters have a very slight convex surface on face. All of my used ones that I removed were nearly flat.
I have a used camshaft from a 1940 216 for $5 if that helps any.

dtm

It is the combination of the convex surface on the bottom of the lifter and the offset from the center of the cam that creates the rotating motion.

Here is another way to think of it. Pushing up on the center of the convex surface will not cause rotation. Likewise, an offset from the cam center will not rotate a flat surface.

Just my thoughts,