1954 M186 rocker bushings & replacement

[mabbonizio]

Hi all,

The rocker arm bushings on my 54 cab are getting pretty loud once the car is warmed up. When I checked the valve clearances I noted a lot of play in the arm bushings. Here is a video of said play :

I have a couple of questions

1- Can I replace these my self (I'm a pretty competent DIYer)

2- Can I either have bushings made, or buy them off the shelf somewhere other than the classic center, and if so how do I know the size?

help me get her running right !



- Mike

[97 SL320]

I'm on a dial up so vids won't work for me.

From what you describe, the rocker shaft will likely be worn as well. New bushings will help but not solve the entire problem.

Bushings of this type generally will be pressed into place then honed to fit, this will take care of some of the shaft wear. ( bushings are undersized when new, think connecting rod pin bushings for full floating pistons. ) But, . .since the center of shaft is worn and not the edges, the bushing can only be made so tight.

What sort of use does this car see? If limited use I'd be OK with bushings being honed on the tight side, pushed over the unworn section to the worn section and call it a day.

[mabbonizio]

Originally Posted by 97 SL320

I'm on a dial up so vids won't work for me.

From what you describe, the rocker shaft will likely be worn as well. New bushings will help but not solve the entire problem.

Bushings of this type generally will be pressed into place then honed to fit, this will take care of some of the shaft wear. ( bushings are undersized when new, think connecting rod pin bushings for full floating pistons. ) But, . .since the center of shaft is worn and not the edges, the bushing can only be made so tight.

What sort of use does this car see? If limited use I'd be OK with bushings being honed on the tight side, pushed over the unworn section to the worn section and call it a day.

I drive this car a good amount for something of its vintage. Roughly ten miles/week then back and forth to a couple good car shows + some beach trips - maybe about 1000 miles/year.

The head was "rebuilt" about ten years ago, and the mechanic did not replace these bushings at the time of rebuild (frustrating)... So I'd feel comfortable replacing all thats worn for the sake of not having to do it for a long time.

I agree that the rocker shaft is worn as well. I'll get price quotes on those, hopefully they aren't insanely expensive.

Sounds like this may not be a DIY task? I was thinking I could remove the whole rocker/shaft assembly and bring it to a machine shop but am anxious about mixing them up upon reassembly. I've heard Mercedes is very anal about keeping the correct rockers with their corresponding cam lobes.

[97 SL320]

The diy portion would include shaft / rocker removal but not much else. You would be able to install the bushings but it is better for the shop to do the job complete as they will have / can make a bushing driver.

Getting new parts prices is a good jumping off point. If new bushings are huge $, there has to be something off the shelf that would work. If the shaft is worn and $, getting it centerless ground then honing bushings to fit is an option. Just make sure the bushings are undersized enough. If lateral play is too much, generic precision shims can be had to take up the clearance

This car has overhead cam where one end of the rocker rides on the cam and the other on the valve tip correct? If so, these designs are relatively immune to swapping parts ( at least for modern engines anyway. ) But it is good practice to keep worn parts together where possible.

If this is a pushrod engine, parts can be swapped without much issue.

Given you drive 1 K per year ( and I'm guessing not much at freeway speeds ) parts that are on the worn side will continue to go for years so don't be too worried.

[mabbonizio]

Alright, last question.. is it safe to take the car out for a spin with worn rocker am bushings or should I wait til I have them redone? The more I use this car the better it runs, if I let it sit too long it start to run poorly!

[97 SL320]

As long as the valve lash is somewhere near correct I'd drive it given your seemingly gentle use.

I'd think your noise may be more camshaft related than bushing wear. Mechanical cams have a gradual initial ramp that takes up lash before the major lift occurs. As this ramp wears out the lash is taken up more rapidly and can lead to noise.

You might have noise from another area, have someone very familiar with engines to have a listen.

For the record I have not worked on your engine type but, have built countless engines over the years on a professional and personal level. My shop has been closed for some years but I still have my own projects going along.