I had the engine on the car rebuilt and when the shop tried to start the car they found out that they had to use new phaser bolts. In less than 10,000 kilometers the engine is overheating and I suspect head gasket. When a 4.6 liter mustang engine is rebuilt do the head bolts need to be replaced? I know the shop purchased news headbolts but after the engine was torn down again to install new phaser bolts I don't think another set of new head bolts would be required?
If by phaser bolts, you mean the phasers on the cams for Variable Valve Timing (VVT), you don't need to remove the heads to do this, so the head bolts should not have been touched the second time around. The cams sit on top of the heads. You'd have to tear down the front of the engine as well as taking the valve covers off, but the heads would stay in place.