My shop CD gives 2 sets of tightening torques for headbolts:
1st
Hex. socket cylinder head screws (with engine cold)
Step 1 70nm
Step 2 90nm
Setting interval 10minutes
Step 3 100nm

2nd
Hex. socket cylinder head screws (with engine cold)
Step 1 40nm
Step 2 70nm
Setting interval 10minutes
Step 3 90degrees
Step 4 90degrees

I take it a "setting interval" is simply a 10 minute wait to allow the headgasket time to "settle"? Is there any difference between the option1 or option2? This seems very strange to me. Thanks, RT

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Yes, ten minutes is just ' getting a cold drink , or cleaning your hands ' time.
I have never seen the " 90 degrees" TWICE information for the 616 or 617... may be there .... but I have never seen it... all I ever saw was a max torque... then ONE 90 Degree additional turn.

There are two types of head bolts which you may encounter on these engines... are you sure those two types of instructions are not meant for those differences... I thought the difference could be told by the type head on the bolt.... ???????????

Not really an answer ... just a heads up... to do more looking before choosing the procedure...

And keep in mind... though you did not ask about it yourself....
that all torque readings are for Clean and LIGHTLY LUBRICATED threads...
To me this means you must run a tap into the block and get out the residue... and wire brush old bolts.... ( much better to use NEW ) ...and that the torque readings will only be close if you put a lubricant onto the threads... preferably in the BLock also... because putting it on the bolt may allow too much of it to be smeared off at the top thread as the bolt hits the block....
This is not new info.... a search will reveal long discussions on this...

RWT,

Greg is correct.

The first set of numbers that you posted is for hex socket cylinder head bolts with a cylindrical shank.

The second set is for double hex socket cylinder head bolts with a "necked down" area between the head and the threads. This set shows the diameter of the "necked down" area to be smaller than the O.D. of the threads. And, you are correct in that these cylinder head bolts get two 90 degree angles of rotation (total of 180) after the setting interval.

I thought that there were two kinds of bolts the 10mm hex head and the star pattern head bolts. These tightening references were for these two distinct types and if you have the star head bolts that require the additional 90 degree turns they are NOT reusable. You must go with new bolts when reinstalling the head.

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

The "hex head" are the "hex socket cylinder head bolts" as I noted above.

The "star pattern" are the "double hex socket cylinder head bolts" as I noted above.

Six point (hex head) are non-stretch bolts.

Twelve point ("star" head) bolts are stretch and get the two 90 degree turns. Benz started using the stretch bolts in the mid 70s, and what you have will determine both the head gasket you use AND the proper torque procedure.

I've not seen many turbo 617's with hex head bolts -- in fact, I don't belive I've seen ANY. Some early non-turbo 617's have them.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

The 12 point bolts that most of us probably have are actually "triple square" despite the unfortunate translation as "double hex" If you look at them carefully you will see that they consisst of three square patterns offset at 30 degree increments. This creates a fastener with 45 degree pressure angles, much better than a "double hex" which would have 60 degrees. The bolts are allowed a maximum of 1-1.5 mm permanent stretch beyond which they must be replaced. 104, 119 and 144mm length M12 bolts are considered serviceable up to 105.5, 120.5 and 145mm length respectively. I had no more than 50% of allowable stretch and reused mine.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

Cleared up my confusion quickly once the semantics got worked out...

I did not know that about the stretch allowed. Very interesting.

__________________
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Thanks guys! I have the head off now. New headbolts to go on and they are the stretch 2X90* kind. See post on "Tearing the head off" for update. RT

__________________
When all else fails, vote from the rooftops!
84' Mercedes Benz 300D Anthracite/black, 171K
03' Volkswagen Jetta TDI blue/black, 93K
93' Chevrolet C2500HD ExCab 6.5TD, Two-tone blue, 252K