M130 Engine Replacement Torque Bolts?

[1971 250/8]

Hello rebuilders. My M130.923 engine is fully disassembled and I need to replace torque bolts for the crankcase pan, manifold bolts, and perhaps a few others. My issue seems to be finding a single source that specializes in metric sizes for Mercedes.

A few questions: Does anyone know which engine bolts are single use torque and must be replaced?

Would replacing torque bolts with studs present a problem? (manifold)

Is anyone familiar with ARP kits? Why don't they have them for Mercedes? They have just about every other car.. including foreign metric engines.

I'm positive these get replaced all the time during engine rebuilds... but I can't find replacements!!

[97 SL320]

To get the terminology correct.

TORX This is a star shaped head that is an improvement over a Allen head as it is less prone to slipping / striping out.

Torque To Yield This is a bolt that stretches assuring that maximum clamping force it attained regardless of the torque it takes to turn it. These became popular in the 80's for cylinder to head bolts. Sometimes they are used on connecting rods and possibly flywheel bolts. A TTY bolt can typically be identified by a shank that is smaller diameter than the threads. A positive identification is when the tightening spec calls for a low initial torque reading then a further tightening of a certain amount of degrees

TTY bolts can generally be reused once but the official factory word is to replace as it can be difficult to determine if they have been reused.

Non TTY bolts can be freely reused if in good condition.

Mercedes tends to push for bolt / nut replacement when they have locking compound or are self locking. In practice bolts can be reused with new locking compound . peening of the nut.

[1971 250/8]

Originally Posted by 97 SL320

To get the terminology correct.

TORX This is a star shaped head that is an improvement over a Allen head as it is less prone to slipping / striping out.

Torque To Yield This is a bolt that stretches assuring that maximum clamping force it attained regardless of the torque it takes to turn it. These became popular in the 80's for cylinder to head bolts. Sometimes they are used on connecting rods and possibly flywheel bolts. A TTY bolt can typically be identified by a shank that is smaller diameter than the threads. A positive identification is when the tightening spec calls for a low initial torque reading then a further tightening of a certain amount of degrees

TTY bolts can generally be reused once but the official factory word is to replace as it can be difficult to determine if they have been reused.

Non TTY bolts can be freely reused if in good condition.

Mercedes tends to push for bolt / nut replacement when they have locking compound or are self locking. In practice bolts can be reused with new locking compound . peening of the nut.

Great to know info. There are no TORX bolts, all are standard metric bolt heads or allen heads. The info on TTY is a tremendous help (thanks!) and the only obvious ones I have seen (slim shank) are the connecting rods.

Any tips on where to get replacements? Machine shop nearby, I suppose I can ask them.

[BWhitmore]

ARP (Automotive Racing Products) are fasteners for race cars of all types. They probably sell fasteners for Mercedes in metric sizes, but unless you are in a racing environment, they are probably overkill.

[Frank Reiner]

Originally Posted by 1971 250/8

The info on TTY is a tremendous help (thanks!) and the only obvious ones I have seen (slim shank) are the connecting rods.

Any tips on where to get replacements? Machine shop nearby, I suppose I can ask them.

The connecting rod bolts do have a necked down section ("slim shank"), and are tightened with the angle-of-rotation process. The new diameter of the necked down section is 8.3/8.4mm; the reuse limit is 8.0mm.

They are specific to the MB rods, and are generally a dealer item, although there may be some aftermarket availability.

[Benz Dr.]

All of this stuff is readily available if you know where to look. MB wold be my last choice.

[1971 250/8]

Originally Posted by Benz Dr.

All of this stuff is readily available if you know where to look. MB wold be my last choice.

Except that it isn't, which is why I'm asking.

[Benz Dr.]

Originally Posted by 1971 250/8

Except that it isn't, which is why I'm asking.

Sure. Try Metrics. They're in CA.

[97 SL320]

And this all comes back to why are you wanting to replace bolts?

[1971 250/8]

Originally Posted by 97 SL320

And this all comes back to why are you wanting to replace bolts?

Mostly due to wear from previous disassemblies. Not all are worn, however since the engine is disassembled I prefer to replace all of them in the areas mentioned.

I called the MB dealer and they are checking stocks... I'll post the result. (I realize I should have done that first... go ahead and smack my icon... )

[97 SL320]

Worn as in the wrench will slip off or worn as in will fail at Pebble Beach?

This is going to be huge $$$ if the bolts are still available. Someone on the diesel side needed 4 clip in nuts for the trans cross member, they are $ 30 each ( thirty ).

If anything, go to the industrial supplier McMaster-Carr , their pricing is good and shipping usually next day.

[1971 250/8]

Originally Posted by 97 SL320

Worn as in the wrench will slip off or worn as in will fail at Pebble Beach?

This is going to be huge $$$ if the bolts are still available. Someone on the diesel side needed 4 clip in nuts for the trans cross member, they are $ 30 each ( thirty ).

If anything, go to the industrial supplier McMaster-Carr , their pricing is good and shipping usually next day.

Attached a picture of the worst head bolt. Note the stretched threads and pitting on the shaft (which is odd since there was no rust... all other bolts are smooth)

All the crankcase bolts need replacing (previous owner over torqued them/broke 2... I broke 3 more trying to remove them..)

I removed all the head studs and will replace all of those.

Finally... just about all propeller nuts and bolts are stripped. Some already were, I did one myself before fabricating a 17mm tite-fit wrench to remove all slop. These are a bear to remove.

YOWZA I hope they don't cost that much!!

[97 SL320]

OK got it. Yep, the head bolts need replaced.

[1971 250/8]

Originally Posted by 97 SL320

OK got it. Yep, the head bolts need replaced.

Turns out my one stop shop is MB dealership. Tried to avoid them but prices were not as bad as what I thought they would be... plus it was worthwhile working with an old pro in the parts shop.

The Head Bolts are 12 bucks each (long) and 9.75 (short)

Propeller shaft nuts/bolts come with the flex joints (which need replacing) and that set me back $98 each (within budget)

The Head studs (11 total) were decently priced at 6.38 (long) and 5.93 (short)

The starter gear bolts were 10.10 each (these are one time use slim shank bolts)

The crankcase bolts were 1.60 (short), 3.42 (mid-size) and 5.70 (long)

They all needed to be ordered, with some coming from Germany.

I have part numbers if anyone needs them.

Thanks for all your input.

---

[Frank Reiner]

Originally Posted by 1971 250/8

The starter gear bolts were 10.10 each (these are one time use slim shank bolts)

If "starter gear" is the flywheel, the necked down bolts have a service limit of the neck diameter, just as with the connecting rod bolts. Almost always they can be reused once, and frequently two or three times before the stretch limit is reached.