I bought a brand new quinn torque wrench with a built in angle system
What is a "quinn" torque wrench?
Most any torque wrench needs to be cycled a couple of times before actual use. Removes excess friction from the mechanism.
I know the ultimate goal is to reach a certain stretch right?
No, the ultimate goal is to reach a certain clamp load on the parts.
TTY bolts--which these are not--have variable stretch, but consistent clamp load.
"Regular" bolts have restricted stretch, are reusable, but inconsistent clamp load. Gotta make sure all threads are in good condition, proper lube, etc.
The "compromise" between TTY and "regular" torquing is Torque-Angle. Reduces the effect of improper lube, damaged/dirty threads, etc.
The "big mistake" folks sometimes make is to lube the underside
of the head bolt washer
(if used) where it touches the head. (Lube the bolt-head-to-washer, but not the washer to cylinder head.) Then the washer spins on the head under torque load, reduces friction, leads to over-torquing and broken fasteners.
I found a first a while back I had not seen. I pulled the OEM 1987 TBI 305 out of the 87 G20. It had torx bit screws for valve cover bolts. It had 104K on it and by all appearences and the hardened condition of the valve cover gaskets had likely never been apart. I cannot think of another 87+ V8 I have seen with center bolt valve covers that had Torx screws holding them on.
Some of the later perimeter-bolt valve covers got inverted-Torx studs, with a kinda-self-locking nut. Nice set-up if your valve covers were thin enough (stamped steel) to work with them. The studs weren't long enough for most cast-aluminum covers.
In theory, once it begins yielding, you don't need to turn it anymore. I think they have these weird procedures because it's easier for the machine to turn X degrees than it is to "feel" it.
I've seen some charts showing the clamping force and it rises up until it yields, then it basically stays the same for a fairly wide range, and then if you keep turning it falls. There's no significant clamping difference anywhere in that plateau, so the beginning of it is just as good as the middle or end. In theory ...
Kinda depends on whether the fastener is Torque-To-Yield (TTY) or merely uses a Torque-Angle procedure on a non-TTY fastener.
TTY fasteners are one-use, disposable. Using a Torque-Angle procecure, but not a TTY bolt, may be reusable. GM is "big" on Torque-Angle head bolts that are not TTY.