Single use bolts

[Crazy Paul]

There's a massive amount of mis-understanding on this Forum surrounding bolts which GM instructions specify to discard after a single use.

There are 2 different reasons why GM will call for a bolt to be discarded.
1) The bolt contains a single use thread sealant (usually a dry powdery blue substance on the threads). In GM speak "Important: Bolts with micro-encapsulated thread sealant must be discarded after removal."
OR
2) The bolt is designed as a Torque to Yield (TTY) bolt, which means the bolt threads are designed to permanently deform at the final specified torque setting.....which prevents the bolt from backing out in service.

Note: TTY bolts may also have thread locking compound on them from factory, eg: head bolts and crank balancer bolt.

How to tell which bolts you can actually re-use.
1) Check the GM specified torque setting for the bolt in question. If there is only 1 torque figure given eg: 30 N·m (23 lb ft). Then if there is any blue goo remaining on the thread you can clean the bolt thread, apply new thread locker/thread sealant and re-use that bolt.
[GM doesn't recommend recyling bolts in this fashion, but there is no real reason you cannot if you wish.]

Which bolts are actually TTY and cannot be re-used.
2) Bolts with an initial torque figure + a stretch (angular measurement).
In the example below the final application of the 150 degrees is the TTY process......the bolt threads are being stretched permanently on purpose.

Example:
Tighten

• Tighten the bolt to 100 N·m (74 lb ft).

• Tighten the crankshaft balancer to crankshaft retaining bolt an additional 150 degrees

[wreckwriter]

Good explanation of an important point. Stuck.

[ULTRA Z]

Very Good Info

[Crazy Paul]

And another important point.
The torque values given by GM in their instructions always refer to stock GM bolt materials.

So if you are replacing a GM bolt with an aftermarket bolt then the GM torque values go out the window.

Case in point....replacing a stock GM TTY crank balancer bolt with an ARP (234-2503) multiple use bolt.

For an ARP bolt use the ARP provided torque value eg: balancer bolt =235 ft/lbs
{Note there is no additional angular twist for ARP (non-TTY) bolts}

Believe it or not you can actually break an ARP bolt by trying to wrongly apply the much lower GM specified torque + an angular twist (for stock GM bolts). The twist part will get you every time if the bolt is not designed to yield. :)