[BillK]

Ken,
They are not torque to yield, however ......

Most of the later model 454's use the "torque plus angle" method of tightening the head bolts.

There is a big misconception that any time a fastener uses the "torque plus angle" method of tightening ( such as 30 ft lbs plus 90 degrees) that it means the fastener is torque to yield. This is not always the case !!! This is simply a more accurate method of getting the required stretch on the fastener.

There are a lot of fasteners (Oliver rod bolts for one) that use the "torque plus angle" method of tighteneing, but are definitely not torque to yield.

Then there are some Honda head bolts that are strictly torqued to a certain ft lb figure, but those bolts are torque to yield and have to be replaced after each use.

Also, torque to yield bolts are certainly used on cast iron heads.