merc 350 top end questions

[gerhuet]

Top end(s) work on MB 350 slc

Hi everybody,

Firstly a great source of parts for MB (and other German marques. They have almost everything for 107 sl’s at a great price), based in the UK web site http://www.kmsparts.com/login.asp .

With deepest winter upon us, I have decided to do a bit of top end work on my 1973 350 slc. It has 114,000 on the clock and is going very well barring high tickover (1200 rpm), sometimes noisy cam chain and an occasional bit of blue smoke at startup.

If I lift the rocker covers will I be able to access the timing rail, top chain rail and chain tensioner. I hope to be able, or at least my local mechanic will hope, to feed the chain in by methods that I have read in this forum. If possible I would like to avoid removing the cam chain cover, yet replace as much as I can.

Secondly I want to replace the valve stem seals (try and cut down on the blue smoke). Does anyone have any tips or experience in these aforementioned items. Special tools required, what to do, what to avoid etc

Any advice much appreciated,

Thanks

Gerry Huet
Wexford
Ireland

huet@eircom.net

[ctaylor738]

Not many 350's over here, but assuming the same basic SOHC design, the seal replacement needs the following tools:

- valve spring compressor (the ones that hook under the cam work well)
- air compressor
- air fitting for spark plug hole
- remote starter switch

The sequence is as follows for each cylinder:

Remove spark plug
Crank engine so valves are closed
Compress the valve spring and remove rocker arm and "hockey puck" pad. If you can't compress the valve enough because it hits the piston, turn the engine a bit more.
Introduce compressed air through the spark plug hole to support the valves
Compress the spring again and remove the collets (sort of little half-round wedges) with needle nose pliers or a magnet. Remove the retainer, spring, and the old seal.
Put a bit of oil of the valve stem and slide the little plastic protector that comes with the seals over the notch in the stem
Slide the new valve seal onto the stem and press it firmly against the head
Remove protector
Reinstall spring, retainer, and collets
Remove air supply
Reinstall hockey puck and rocker arm

At the end, reinstall the plugs, and button up everything else and you should be good to go

I predict it will take you 20 minutes to do the first, and 2 minutes to do the last.

[gerhuet]

Thanks Chuck, seems straightforward enough.

The 350 is exactly the same as the 450 only with a shorter stroke. Redline is at about 6,250 rpm. Great exhaust music up around there.

Thanks

Gerry

[Strife]

Depending on how much your time is worth and/or how much ingenuity you have, having the "right" tools is very helpful. With the idea that I might sell these later on eBay used (or maybe rent them out), I bought:

Valve stem seal installers, 9 and 11 mm (like $30 each; this was probably overkill)

Valve stem pliers (not very expensive, $15)

A pin removal tool (for the tensioning arm and guides ($60))

A valve compressor (no way around it, this is expensive and you need it; I've heard that some people have managed with valve compressors not meant for this engine, but the way I looked at it, I can't afford to screw up ($150)).

A sort of "cap/guide" for the chain that screws over the front cam bearing and cages the chain in place so it can't fall off. Supposedly, this tool turns this into a one-man operation. The way I look at it, if the chain falls off, the car would go on a flatbed to a shop, and I would go to the hospital with a stroke, so it was insurance ($50)

I plan to rent a compressor and buy the spark plug adapter locally. I might have a friend actually weld-up this adapter for me.