Very possible to damage crank, bearings, etc. Somwhat depends on just how much wear on lifters and cam. Had a anti rotation yoky bust on one of my engines perty much toasted everything.
What engine do you have?
I have the 460, smog'd. 77 with D3VE heads. Came with the retarded crank sprocket, replaced with 0º sprocket. No performance upgrades. These engines were designed to run the way they are, so I'm happy with that. The retarded cam timing was the only thing that was really a bandaid to pass emissions and caused it to run hot and put the peak torque at an unusable high RPM.
PSIG, you've been very helpful. I'll drop the oil now and fill with Rotella T conventional diesel oil with a dose of zinc additive for first startup until the short oil drop (meaning I'm dropping the oil immediately after high-rev break-in and a few spirited runs to let the oil pressure and mist wash everything as best it can). Sticking with Motorcraft filter. Check the metal content (just sweep the oil drain pan with a magnet) and report back with that.
My timing was spot on when I took the distributor off, and everything was set to #1 and marked, so I should be absolutely close enough to start and idle high. I will have timing light clamped and in-hand. I'll unplug the vacuum choke pull-down so I will have plenty of time to slide a small shim under the throttle arm.
I'll be bleeding the radiator at the same time with a strong air-mover over the block itself so it won't stagnate.
The lobes will have plenty of the assembly grease on it and the lifters will have soaked in oil before hand, with the contact faces greased as well.
The manifold gasket will have set for at least 6-hours before starting. The last time, I did this so the RTV on the china wall will cure and had no issue with it what-so-ever. I know to retorque the manifold and carb bolts after letting it warm up too.
Would lowering oil viscosity help the oil squeeze into the bearings and prolong their remaining service time? Or would heavier oil allow it to stay in place and form a thicker film? I'm sticking with the Rotella T conventional diesel stuff either way.
You guys have been great. I'll post a video of it once it's running too!