Valve Adjustment Clearance .08/.18 mm vs. .10/.20 mm

[Iconic]

How come my BBB (page 00-0/4) states the valve clearance should be .10 mm for intake and .20 mm for exhaust and our technical manual states .08 mm and .18 respectively?
What am I missing here? Are the .08/.18 values for a 230 or 250?
Mine is a '70 280 SL.
My engine will be cool in the morning, so I will adjust then. My first time. 
Head re-torque went smoothly.

[66andBlue]

The 0.08/0.10 mm  numbers came from the  Mercedes "Technical Data Passenger Cars" 1966 booklet and the BBB for the 230SL.
My BBB (for Passenger Cars Starting 1968 - printed Aug. 1970) shows on page 00-0/4 the following values (for a cold engine):  intake: 0.08 mm {or 0.12 mm if the outside temperatures are below -25̊ C for longer periods}; exhaust: 0.20 mm.
Since you brought up the discrepancy I have checked the 1969 Technical Data book edition and the value for the intake stayed the same but the exhaust valve clearance in a 230SL (M127) engine was revised to 0.20 mm. 
The 1971 edition shows the same numbers 0.08/0.20 mm for the 280SL engines. 
Thanks for bringing this up. I'll correct the value for the exhaust valves in the technical manual.

[SteveK]

This is a good catch and very interesting.  I have a BBB entitled "Service Manual Passenger Cars Starting 1968" and it does shows the .1 and the .2 on 00-0/4. 

I adjusted my valves a few weeks ago based on what was in the Tech Manual which also matches what is in the Haynes book (.08 and .18) and all seems fine.  I have a late 280SL engine. 

It would be really nice to know which one is right

[66andBlue]

Oops, Steve we posted at almost the same time. See my revision.
And just to be complete, the 0.08/0.20 mm values are also correct for a 250SL.
The 0.10 mm value for the intake valve shown on page 00-0/4 is for the 300SEL/8 6.3!

[SteveK]

Alfred, thanks for clarifying.  I'll probably adjust my exhaust valves to the .2 tomorrow just to see if it does anything.   

[Iconic]

And just to be complete, the 0.08/0.20 mm values are also correct for a 250SL.
The 0.10 mm value for the intake valve shown on page 00-0/4 is for the 300SEL/8 6.3!

Guys, thanks for all the input.
Alfred,
I will attach my BBB page which shows .10 mm for the intake side for the 280 SL and .20 mm for the exhaust side.
I hope you can read it.
My BBB has a May 1971 supplement in the back, but I don't see what year/edition it is.
This is a pretty small difference, and since there seems to be changes in the values as the BBB changes editions, I'm not too worried about it...
But it is interesting that it changed as they were printing new additions.
Temperature seems to be a factor, so in reality, it should be different on 50 degree F day and a 85 degree F day.

[Naj ✝︎]

A bit off topic but these manuals always say:

""For electrode gap, thread lenghts, list of approved spark plugs etc. refer to the Spark Plug Table""

Has anyone ever seen one of these tables?

naj

[SteveK]

Icon, I just checked and my BBB is identical to yours and its marked as a July 1973 Supplement.  My suspicion now is that the change in values has something to do with emission controls. 

The slightly larger gaps would mean that the valves will open a hair later, not open as wide and close a hair earlier and I would guess lead to a slight higher compression.  I'm going to think about this more before I start playing, but would love to hear comments.

[ja17]

Hello,

Consider that ambient temperature will vary and the wear on all the little valve train parts will cause minor inaccuracies. Such a minor variation should not cause any issues. 

I have always used .007" exhaust and .003" intake on used engines with the knowledge that the minor wear will make the adjustment a little looser than set.  The valve train in these engines will normally"wear loose" between adjustments.  In other words the valve adjustments normally become looser as operating time goes on. I suspect that the standard temperature for setting valves would be 68 deg. F . (std. lab temp.) Minor variations would occur above or below this temperature in any case. Anyway, don't loose any sleep over such minor details. Be more concerned about doing the adjustment accurately and identifying any wear problems which may throw your measurements off.

[Iconic]

Thank you all once again.
My first valve adjustment (first valve adj on an MB, that is) is complete and successful.
I broke my 10 mm allen head socket when trying to loosen my first head bolt (brand S&K). That was scary  .
It broke at less than 120 ft-lbs. So, it must have had a defect of some kind.
After buying a new 10 mm, all loosened with less than 120 ft-lbs.
All valve adjusted without needing to remove the rocker arm and use a 6-point socket.
Three of my intakes were "very" loose (greater than 0.15 mm clearance).
I can't believe how the car feels, revs, sounds, pulls, and shifts  BETTER.
I wouldn't have done it without the website. Thanks to all !