I used the 70 mm bolts with the helicoils. Helicoil length info attached.
Bolts have M8 threads.

Attached Thumbnails

 

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1986 300E (3/2002) Rear ended and totaled (10/2009)
2000 Xterra (5/2000)
1992 400E (11/2009) -Sold
1986 300E (12/2009) - Sold
2004 E500 Wagon (6/2013) - Sold

Thank you for that answer on the length of helicoil, hs 300e

the 73mm bolts won't help you on the bolts with inserts.


I'd go 1.5 diameters with a helicoil on aluminum(if possible).
1.5X8mm= 12mm if you have the depth.


Michael

Searched through threads to no avail. Can anyone tell me the allowable stretch of a m103 head bolt, (mine are w/ washers) and the PROPER way to torque them (with specs) when re assembling head to block. Also does Peach Parts sell the "Preferred" head gskt set? Thanks guys and gals, this site is AWSOME because of you............
Have a great weekend!!!

Most of the answers are here:
factory service manual

There are some very good inputs by forum members

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'88 300TE, 175k, black RENNTech 3.6L Recaro C's AMG 1 SOLD
'92 500E, 110k, Spruce green, stock SOLD
'94 E320 Cabriolet, 130k, E500 wheels, Emerald green SOLD
'94 E320 Cabriolet, 110k, black, stock, SOLD
'88 300TE, 229k, dark grey, SOLD
'90 300CE, 212k, white, new paint, SOLD
'91 300E, 209k, white, rebuilt head SOLD
'74 914-6, grey, 2.7L 325hp twin turbo Audi conversion

I didn't realize that reading a manual was a pre-requisite to asking questions on this forum. Not everyone on this forum has a service manual or access to one. I thought one of the functions of this forum was for people to help people. If someone on this forum ask a question that I know the answer to, then I just give them the answer or help them any way I can. IF I had a manual, do you really think I'd have to ask the technical questions I've asked. Thanks for your reply and link--but you really didn't answer my questions.

No "pre-requisite", I provided the manual because it was apparent you didn't have it. If you don't see that as helping, you have a skewed expectation...

__________________
'88 300TE, 175k, black RENNTech 3.6L Recaro C's AMG 1 SOLD
'92 500E, 110k, Spruce green, stock SOLD
'94 E320 Cabriolet, 130k, E500 wheels, Emerald green SOLD
'94 E320 Cabriolet, 110k, black, stock, SOLD
'88 300TE, 229k, dark grey, SOLD
'90 300CE, 212k, white, new paint, SOLD
'91 300E, 209k, white, rebuilt head SOLD
'74 914-6, grey, 2.7L 325hp twin turbo Audi conversion

pifcat2
Again, Thanks for the link (very helpful) and your time in the form of a reply. Nothing "skewed" about asking a question and "Expecting" an answer............