Guest Post: W116 450SE – M117 Rocker Arm Wear

Editors Note: This is part three in a series by Nick Gruzevskis about owning a 1978 Mercedes 450SE W116.  The first part covered the purchase and cosmetic restoration and the second covered some further maintenance.

It’s been a while since I’ve been able to write, as after work hours my focus had been on organising the MBCV 2025 Mercedes-Benz Concours d’Elegance. As the event occurred on March 16th, I now can write about engine work undertaken on my 450SE late last year.

My mechanical knowledge is limited, but I’ve known since I acquired my 450SE that I had a problem in the top end of the engine. There has always been a mechanical ticking noise when the M117 4.5 engine was warming up and even when warm I could often hear a faint ticking noise.

After procrastinating for years, I was determined to fix the issue, so took it to my mechanic, who promptly diagnosed worn rocker arms, and scoring on the camshafts.

You can see a trough where the rocker is worn, pitting in the chrome cap. It’s not typically to see this wear on a healthy engine.  It is usually observed on cars that have had dirty oil, poor oil supply, or a general lack of maintenance. In my case, my 450SE was laid up for many years, prior to purchasing. I suspect there was a lack of maintenance, contributing to this problem and expensive fix.

You can see the deep pitting on the chrome cap. This was the worst of all rocker arms, but there was wear on most of others.

You can see the scoring on the camshaft lobes.

What’s a rocker arm? In an overhead cam engine, the camshaft must have something to push on to actuate the valve. The rocker arm is somewhat the sacrificial piece of metal that goes between the valve and the camshaft. Symptoms of worn rocker arm wear is a deep knocking noise. Apparently, the nose is more persuasive of bigger engines, V8 engines as they have short stubby rocker arms.

I have a great relationship with my mechanic, he provided a list of parts required and asked me to source them. It took me sometime work through and order what was required, sourcing them from Pelican Parts and Niemoeller.

The other task was to get both the camshafts re-ground and hardened. I used Tighe Cams for this work, as they came highly recommended from an MBCV member. The work cost $850 and took them about a month to complete. The camshaft work was excellent and as it was the last of the parts required, so the engine could now be setup.

Luckily, I had ordered two new sprockets, as the teeth on the original parts were quite worn when compared to the new sprockets. A few years ago, I had replaced timing chain, tensioner and guides, so there was no need to do this this time.

My mechanic had a set of various sizes of valve adjustment shims (also known as buckets), as we weren’t sure what sizes to order. To be my surprise, every shim required was 5.1mm, meaning there wasn’t much valve wear.

Once the work was completed, I was stunned at how much quitter and refined the engine was, especially at idle. As I had nothing to do within my ownership, originally, I just assumed the roughness was normal.

Was it worth it to do this work, absolutely, as every time I drove the car prior, I would hear the ticking noise and would just get annoyed that the car wasn’t right. Many of you will know what I’m talking about.

Author:  Nick Gruzevskis is a contributor to classicjalopy.com, and the custodian of a great collection of classic and modern cars.  Links to some his other articles can be found here