It may just be the "Old's-COOL" mechanic in me (or the fear the guy I apprenticed under might hop back out of his grave and wack me 'up-side' the head for not following good procedures
) - but ... I always run an engine to heat soak and break-in internals and then allow to cool before re-checking all the torque setting (heads, manifolds, fittings & etc.) and then go test drive or dyno it.
I know the majority of composite gasket suppliers say 'it's not necessary' - but what can it hurt?
Besides, I've ran into way more than one that a bolt or two DID move some while going through torque pattern again!
As stated, no need to back them off - just set your torque wrench to recommended setting and run the bolt pattern again to check the final torque.
The Sealer you use on the bolt ends should be a non-hardening type - in other words, it should not dry hard and should be somewhat pliable even after it is 'set-up' (even years later when the engine is disassembled again).
Permatex 'Aviation Form-A-Gasket' #3 liquid in the small can is a great product for use in this area, as well as most of the wet contact seal areas (like the coolant gaskets, timing cover seal outer edge and other seal mating edges).
GM also sells a very good product, but it is only available in the 'large-economy' size, so a can would be a lifetime supply to most ...
Truthfully, the SBC design (along with many other truck/fleet engines) is so robust and forgiving, that even if you didn't re-torque steel-shim gaskets (GM didn't
) it would probably still lead a long and healthy life unless severely overheated or abused.
The shop I apprenticed in in the early 60's had a "Flat-Rate Freddie
" mechanic that only liked to work on the fleet trucks and buses for the city and county - because no-one opened the hood when they picked it up to check the quality of work you did ...
He only had one 1/2" impact gun, a set of deep impact sockets - 1/2" drive, maybe 5~6 wrenches (2 - 9/16" I think
) and some really beat up "Pry-Drivers" (screwdrivers that seldom saw a screw in their life, just used to 'pry' $hit apart ...) and a couple other tools, all that could double as ' the hammer of Thor'
when needed ...
He had a surprizingly (to me anyway) low 'come-back' rate
He NEVER torqued ANYTHING! He removed and installed heads with an impact
This guy would knock an engine apart with his mighty impact, smack the retainers off the valves, grind the valves and seats and reassemble - without EVER touching the rocker(s) or their adjustment! - then just reassemble and re-install ... and only touch the rocker adjustment if the lifter had a noticable tick
Watched him do it hundreds (literally) of times and 99% of them he never adjusted anything before signing the card and turning it in - they never seemed to have problems and seldom came back on him - still don't know why ...
He rebuilt huge truck rearends - with an impact - no dial indicator!
He did hundreds of manual trans overhauls - same impact ...
Never cleaned a part, painted a part or wiped grease off a door handle or steering wheel in his life.
Hardly ever used any gasket sealant - just slapped them on dry - said " if they needed sealer the parts store would have sent it "
- or something like that.
And he told the raunchiest jokes I've ever heard
He was hardly ever allowed to do regular customer work
(I did all the carburetor, electrical, performance and high-dollar stuff - you know, any work that required being clean, detail oriented or painted before the customer got to see it or get it back
So anyway ... long story to illustrate how forgiving an engine can be ...
But, don't follow his example