Your dream of turning the engine over but having it stuck is probably coming from something that often gets overlooked by people, open valves during storage.
I just got a Model T that had been under a car-port here in California. Someone had removed the #2 sparkplug long ago, and had removed the hood and everything, leaving it exposed to the air. No direct water ever got on it, but that's not good at all because there's water in the air and it condenses n anything it can when temperatures change.
This particular engine that was in the car was stuck.
I removed the head.
This is important:
Cylinder #2, which had been open was just fine. #3 was rusted with bright orange rust. There was a large dead insect on top of the piston. It had its spark plug still in and had been in a closed engine the whole time since being parked in 1972. The water galleries and head gasket were fine with no leakage. How did this come about?
I have the engine freed up now and did not have to rebuild it, so please read on, and this applies to most any car engine.
Here's the deal: When you park a car, there is unconditionally one or more valves open no matter where the crank stops. The car in my case had been parked in 1972 and not touched since. With an exhaust valve open slightly where it landed, it was exposed to the outside air via the exhast manifold and exhaust pipe.
There were large thin flakes from the wall of the cylinder raised off of the walls and it was very ugly.
If you store a car, it is best to turn it over, even without starting it, once a month so that the valves are operated and the cylinder exposed to air gets changed.
Remedy: Got a car that's been sitting for a decade or more? ALWAYS remove the heads and inspect. No Matter What! You will save yourself a rebuild nearly every time.
Once the heads are off, use a screwdriver to scrape at whatever rust is in there. Don't gouge the cylinder walls, but just go for the scale and loose stuff. Vacuum out. Now go back in with a rag wrapped around the screwdriver and try to be a little more aggressive.
After that's as clean as its going to get, drop marvel mystery oil in and walk away for 24 hours, repeating at least once. Put in enough to create a standing pool that will hopefully penetrate and soak in. It works even better if the top of the piston is parallel to the ground, but that's tough in a V8 without removing the engine.
If the rust is particularly bad, and you think that pouring liquid in will create a standing pool, you can use household vinegar which will dissolve the rust in 48 hours. You'll have to drop the oil pan to get the vinegar out, but you want to skip removing the block from the car, right? Suck out vinegar after 48 hours of refilling it so that it is immersed and soaking and replace vinegar with Marvel oil as described above.
You now have a rusted cylinder that hopefully has oily rust or dissolved oily rust, you now need to try to move the crank. Guess which way you want to turn? The piston must move down its bore, irrespective of the normal rotation of the engine - reversing the spin is OK. NEVER push the piston up the cylinder. You will not be able to tell which direction of rotation is up with the head on, so those have to come off for this reason alone, but you have to do the cleanout first, so it's all related.
There will be all sorts of junk on the cylinder wall. If you try to start the car, and the piston gets jammed upwards though a hole that's too small due to rust, you'll scrape all the rust off the wall with the rings. The rings will be destroyed, and you'll have a smokescreen of oil pouring out the pipe brcause the rings are no longer sealing or have shattered into fragments or whatever.
Dragging the piston down will hopefully mean that the rings are traversing cleaner walls that were not exposed to air and water (sealed off by rings) and won't be damaged.
Take the piston to bottom and leave it there. Take a rag and clean out the cylinder, getting what's left dry for inspection. Let's assume that there are no giant pits or holes or whatever that would be a deal-breaker. Use moderate grit sandpaper or emerycloth and sand the walls of the cylinder so that they are approximately smooth with no major irregularities. Get a cylinder hone, the sort with 3 long thin vertical stones and a flex driveshaft (not the bristle-brush type) and use a medium or fine stone. I like fine with lots more grinding time personally.
Make certain that as you spin the hone, that you move it up and down vigorously so that the scores that you're honing into the cylinder wall are not horizontal and in the same plane as the top of the block or parallel to the piston rings.
On mine, it took maybe 5 minutes of alternating between honing and using compressed air to blow dust out before I wound up with a semi-smooth surface. I don't know how fast a power drill spins, but if it spins at 1000 RPM, then that was maybe 3000 revolutions of honing. You'll never do that by hand, so get a hone to do this job. Vacuum out and clean cylinder with a rag.
Once done, I drop more marvel oil in, making sure to get all the way around the piston, especially at the top. Wipe it all over the cylinder wall.
Crank the engine now by hand. You've already lubed the other pistons, right? Pull the cylinder(s) that you've been working on to top-dead-center. You'll now have a rusty piston right up on top where you can get to it. Cover all exposed parts that like to be kept clean. Wire wheel that guy and clean it off. Shop vac off the top. repeat for other piston tops. Wipe clean and drizzle more lubricant into the crack where the rings are. I use a giant syringe for that, but you can use a turkey baster or whatever.
Crank the engine over by hand and loosen it through motion. Keep the cylinder walls wet with oil. When you get it moving freely, you're almost home. Drop the pan if you feel it needed. Clean and reinstall. Put in fresh oil. I like thicker stuff like 20/50. Reinstall the heads without the valvetrain and the plugs off. Torque to spec. Now that this is all done, you can crank the engine with the starter and spin it faster and see what happens. You should have a free-moving engine that is ready to be reassembled and run.
You have had a chance to have the heads off and have wire-wheeled them (I hope), so the combustion chambers and everything else is clean, right? Rewire/reinstall the plugs and start her up. Chances are that the thing will run. There may be some blow-by on that cylinder if the rings are not sealing properly, but it may improve with several miles of use, so don't be too concerned about a little oil vapor coming out the rear of the car. Some of that will be the oil that's in the rings and all.
You may get the heads off and realize the engine' is dead frozen and rusted solid, but I would bet against it. I would also bet against the engine being siezed on the bottom end, unless your car had an oil pump problem (unlikely), or was started without any water in the cooling system, which sould cause lots of bad things, including pistons and block getting swollen together from heat.
Hope that helps. It's a bunch of seemingly extra work as opposed to just starting the car up and driving it as one would wish, but this could make a huge difference in how your engine works over the long run, and could allow you to skip a rebuild for awhile.
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