Head bolts / non-turbo
05-24-2016, 04:47 PM
#1
Junior Member
Thread Starter
Head bolts / non-turbo
Hello all,
I have a new to me 1979 300D, I have oil in my coolant so I needed a head gasket.
I have the head removed currently and its at the machine shop getting a basic valve job and checked for cracks / warp.
I had a mismatch of head bolts on the engine, I cant find anywhere in the factory manual where it says which one should be 12 point and which should be 6 point, or what length goes where. I wanted to make sure I have the right type of bolt for each position for reassembly. I planned on purchasing new bolts regardless if they are within stretch limits or not.
Currently bolts in position 14, 13, 6, 4, 12 and 20 are 12 point head and are the same length. All the rest are 6 point. In the manual there are different torque specs for a 6 point vs 12 point bolt. I don't think I have the right bolts.
Does anyone know what bolt goes where?
Thanks!
I have a new to me 1979 300D, I have oil in my coolant so I needed a head gasket.
I have the head removed currently and its at the machine shop getting a basic valve job and checked for cracks / warp.
I had a mismatch of head bolts on the engine, I cant find anywhere in the factory manual where it says which one should be 12 point and which should be 6 point, or what length goes where. I wanted to make sure I have the right type of bolt for each position for reassembly. I planned on purchasing new bolts regardless if they are within stretch limits or not.
Currently bolts in position 14, 13, 6, 4, 12 and 20 are 12 point head and are the same length. All the rest are 6 point. In the manual there are different torque specs for a 6 point vs 12 point bolt. I don't think I have the right bolts.
Does anyone know what bolt goes where?
Thanks!
05-24-2016, 09:53 PM
#4
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2013 ML350 Bluetec
As far as the length of bolt goes, a bit of measuring with calipers (head thickness) and a depth guage (block bolt hole depth) and some arithmetic should answer that question.
05-25-2016, 02:13 PM
#5
Junior Member
Thread Starter
So I got a call from my machine shop. The head is warped, they said it's about 3-4 thousandths out. Pressure test checked out okay. They quoted me 400 to disassemble, clean, pressure test, mill the head, and a valve job with new valve seals.
My VIN is;
123 130 02 111381
Production date 9/78
My VIN is;
123 130 02 111381
Production date 9/78
09-06-2016, 01:05 AM
#6
Junior Member
Plutoe is a troll phishing for your VIN, you should remove it from your post ASAP!
6 and 12 point bolts CANNOT be mixed.
Your engine can only use 6 point bolts. 12 point bolts will not torque correctly because the block is threaded deeper for engines that use the 12 point bolts.
Which is why your headgasket failed, the 12 point bolts were bottoming out in the bore rather than compressing the headgasket.
The headbolt section is 01-405 in the factory 1982+ service manual.
Torque
70 Nm
90 Nm
Let set for 10 minutes
100 Nm
6 and 12 point bolts CANNOT be mixed.
Your engine can only use 6 point bolts. 12 point bolts will not torque correctly because the block is threaded deeper for engines that use the 12 point bolts.
Which is why your headgasket failed, the 12 point bolts were bottoming out in the bore rather than compressing the headgasket.
The headbolt section is 01-405 in the factory 1982+ service manual.
Torque
70 Nm
90 Nm
Let set for 10 minutes
100 Nm
Last edited by OM617.95; 09-06-2016 at 01:08 AM.
10-09-2022, 09:56 AM
#7
Senior Member
DO NOT have the hear refaced. It is well with-in specs. Proper re-facing requires removal of all the valve guides and anything on top of the head, then resurfacing BOTH sides to keep them parallel---that is uniform THICKNESS. The cam runs in pedestals bolted onto the head and they must be uniform bearing heights. Mercedes does make SHIMS for the pedestals if needed.
