1977 450SL - Valve steam seals

[das5150]

Hey gang! Been searching and cannot find a good source of info for research on this project. I would like to do the valve seals on my 1977 450SL as it has been sitting for 10 years and smokes at idle/start up.
I was hoping there would be a step-by-step guide with pictures and all that. Anybody have a link? Also, opinions.... difficult? Seems like it could be quite easy with the OHC setup. Or maybe MORE difficult? Haha... could go either way. Comments welcome!

[das5150]

Be it known that I performed the same task on an old Dodge 440 about 20 years ago at the tender age of 22. I remember it taking a while, but going fairly well. I had MUCH more patience back then...

[Stumps]

das5150, I did the job on my 1971 350SL about 5 years ago and had great success....had all the signs of post idle and overrun smoke, poor vacuum, D-Jet pain etc.

I guess the guides have to be in good condition to be worth doing the job..and sort of a Catch22 to confirm that without removing valve springs etc, so went ahead with the stem seal job and checked guide wear as I went along...fortunately all guides were quite good.

The original stem seals removed were basically rock hard and worn, so sealing was next to non existent. The replacement stem seals appear to be improved design and material.

It took me 2 weekends to do from memory...incredibly slow and tedious at the start to smooth towards the last cylinders. The trickiest part for me was getting the collets out and in...ended up using some sort of home made pick.
Required tool is of course an OHC valve spring compressor (many brands available) and in addition I also used a compressed air fitting into the plug hole to be sure I didn't drop the valve... but not really required if you ensure the piston is at TDC (well on my 3.5 at least). Other than that, just some good back fitness and well thought out planning and patience!

The job transformed my engine...runs sweet since.


Good luck.