I have a 2007 cobalt 2.4 l "B" engine. I replaced head gasket and bolts ,Victor, torqued and additional turn degree to specs. I then had to remove the head again, so can I reuse and retorque these new bolts?
Engine never run.

 

Short answer - I wouldn't do it.

Once the bolt has been "stretched" you will (almost) never get a proper torque value on it again.

You might get lucky but I wouldn't want to chance it for the cost of a set of head bolts......

 

Just buy a set of ARP head studs. Better holding and you don't have to replace them

 

The problem is, whether the engine was run or not, when you do that additional angle turn, you actually push the bolt into it's elastic range and right to the end of it, to the point where it can distort a little bit. While you should be ok because the bolts have never been heat cycled or subjected to any force of combustion, as mentioned above you may not get the same actual torque, because now you are stretching bolts that have been stretched once.

I would re-use them only if you had no intentions of making any real power with the engine. The stock MLS head gasket (which is also one time use for the same reasons) will take up plenty of slack, but may be more prone to failure under heavy boost or extended high-rpm use than a motor with new stock head bolts and a fresh gasket.

 

Get new bolts end of story