Valve Adjustment Setting

[jeffc280sl]

I have a 1970 280SL.  The Haynes manual says the valves should be set cold as follows:

Exhaust  .18 mm
Intake   .08 mm

The BBB says:

Exhaust .20 mm
Intake  .10 mm

I've used the BBB settings.  What do you use?


Jeff C.
1970 280SL 4-speed

[A Dalton]

I use .003 and .007

[jeffc280sl]

Thanks,

That's the same as the Haynes settings.  Should I reset the valves to these settings?

Thanks

Jeff C.
1970 280SL 4-speed

[ja17]

Hello,
The metric/english feeler guage sets round off the settings slightly. I use .004" and .007" which is close to BBB specs.

I like to tighten the ball adjuster until the feeler guage is locked then loosen the adjuster until the guage can be slid free with some resistance.
This method will help keep your feeler guages from getting all bent up.

Using two sets of feeler guages saves a lot of fumbling around and prevents mistakes. Open one for exhaust the other for intake. Identify the intake valves they are on one side directly across from their injectors. The exhaust are on the other side.

Hooking a remote starter to the nuetral safety switch plug on the firewall will make turning the engine simple. I always remove the spark plugs when adjusting the valves, this also helps turning the engine.

Joe Alexander
Blacklick, Ohio

[jeffc280sl]

Thanks Joe,

The conversion for your settings works out to .1016 and .1778mm.  I did use two feeler gauges as you suggested.  Is it prudent to reset the exhaust valves or just leave it alone.



Jeff C.
1970 280SL 4-speed

[ja17]

Hello Jeff,
You should be fine. Problems occure when valves become too tight and do not close. The hot blow-by gases may cause the edge of the valve to burn.

With this type of valve train, the adjustments  tend to loosen up during normal use.

If you run across a valve adjustment which is constantly too tight, this may indicate a mechanical problem with the valve adjuster, the valve  or the head.

Valves lash (clearence) tends to be looser when cold. Parts expand when hot making valve lash tighter. This is why adjustment figures are normally given on cold engines.

Now one could ask the question "exactly what temperature is a cold engine ?".

I am sure Mercedes Engineers have designed some plus or minus safety factors in these valve setting figures.



Joe Alexander
Blacklick, Ohio

[A Dalton]

<<Now one could ask the question "exactly what temperature is a cold engine ?". >>
 Good question ... I always interpret that to mean approx. 20C .
[ room temp]

[Ben]

I normally leave the car overnight and do the valves first thing next morning before staring the engine at all !

Regards,
Ben in Ireland.
'64 230SL 4sp.

[Vince Canepa]

Starrett makes a handy thickness gage holder.  It isn't very expensive and I think it makes holding the feelers much more "comfortable".  Here's the link:

http://catalog.starrett.com/catalog/catalog/groupf.asp?groupid=343

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[Cees Klumper]

That's what I do also Ben. Usually I do my service in 'normal' weather conditions, because I only have limited heating capacity in my garage. I reckon usually the temperature will be between 15-20 degrees celsius.

Cees Klumper in Amsterdam
'69 white 280 SL automatic

[Naj ✝︎]

Vince,
Do you have to buy the feeler strip in 20' or 25' rolls or are smaller lengths available?
naj

65 230SL
68 280SL

[jeffc280sl]

The BBB suggests that the intake valves be adjusted to .15mm from .10mm if ambient temperatures are below -20C for long periods.

Jeff C.
1970 280SL 4-speed

[Benz Dr.]

.003 ans .007 is best as any more than that and the valve rockers make a lot of noise. Actually the clearance gets larger as the engine heats up. I think the cam bearings expand a bit and make the gap larger. The valve stems expand too but not that much.

 All I know is if you set the valves and one is a bit too loose it gets really loose when fully warmed. Any flat spots on the cam lobe will really make it knock.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org

[Bob G ✝︎]

Perhaps this is a proceeder that we could better cover in the technical manual with some pictures of each step and what tools are needed.

Bob Geco

[Vince Canepa]

I just buy replacement feelers for a normal Starrett feeler gage set - 3" long or so.  I get them from a local Starrett supplier.  None of this stuff is terribly expensive and it is actually surprisingly handy.  I also use .003" and .007" and have for years.  I remember the tech at dealer telling me they would set the intakes to .004" if people took the cars into very cold weather a lot, mostly to ensure the intakes stay gas tight when the engine is subjected to really cold temps (outside a ski lodge perhaps).

Vince Canepa
1967 250SL
113.043-10-001543
568H Signal Red
116 Caviar MB-Tex

[HarryMead]

Snap-on had a tool, S-6014, designed specifically for Mercedes valve adjustment, to be used with a torque wrench as prescribed in the BBB.  That, plus a 27 mm. socket to turn the crankshaft and the two feeler gauges, makes it easy to adjust the valves.

Harry Mead (1970 280SL, no air conditioning, 4-speed)

[ja17]

Hello,

I also use .007" and .003 for valve adjustment. It not a perfect conversion from the metric dimentions of .20mm and .10mm but extremely close. As Jeff noticed the US conversion is just a bit tighter but well within any experts specifications. Also a used engine will have some wear and probably could use a bit tighter adjustment.

Trying to push a thin .003" feeler guage in and out can be difficult. Try backing off the adjustment until the feeler guage is locked between the rocker surface and cam lobe then loosen the adjuster until the feeler guage can be pulled out with  some resistance works best and keeps your feeler gauge from getting bent up.




Joe Alexander
Blacklick, Ohio