It's possible that the rings are rusted to the cylinder walls and can be replaced. It's also possible that the connecting rod is seized and can be replaced. Look for those two areas.

If the engine was running, and suddenly stopped, did it make a loud BANG, or did it just sort of slow down and then refuse to turn, using a wrench or large pliers?
If either of those questions apply to your engine, i'd say you might just as well go buy a new short block, and transfer the parts from the blown engine to the new one, such as carburetor, flywheel, cylinder head and ignition parts.
And, don't forget new oil before you start it, if you get that far. From your questions, might i advise you to seek professional help! With these modern engines, they do not take kindly to some inexperienced person messing with their innards, or outer parts, either! Spend a little-save a lot!

For rustyj -- The engine "came with no oil in the crankcase." That's how it was when I bought it -- no oil, and seized up. I am new to small engines, but not new to engines and machinery. I started this thread to see what other people's experiences were. My goal is to be able to work on these engines as I restore the lawn tractors they came in. I have three Allis Chalmers and one on the way. If I contract all of that engine work out, I can't afford it. So I will master the small engines, eventually. Now are you saying that a flat head single cylinder Briggs and Stratton from 1977 is a modern engine? Frankly, I don't have any desire to work on OHV or OHC models. I like old iron. Can you tell me how to determine if the cam and crankshaft are timed properly without splitting the engine?

Marvel Mystery Oil in the cylinder and a pipe wrench should do the trick. IMO the 8hp Briggs is like the Ford 300 six of the small engine world

Well, i think you will be pleasantly surprised when you get the crankshaft to turn! If you do. Get a 5 gallon bucket, dump the engine block into it, fill with drain oil, allow to soak for 6 weeks, then reassemble it all, and try to turn it. I know you will be pleasantly surprised when you learn that----it didn't do any good, so you must dismantle the engine, which from your statement you don't want to do.
Know this: There aren't any short-cuts in engine repair, especially severely stuck engines! The only good thing about them is the fact you might be able to salvage the carburetor, and the ignition coil and possibly the flywheel and spark plug! And then, if you haven't found a good engine, used, go buy a short block. Know this: You might open it up, and find lots of things broken and stuck inside! How do i know this? Been there, found that!
I was given a really nice dark gray Craftsman lawn tractor, with a stuck engine. Just today, i used the ignition coil from it, and some carburetor parts, to get another machine back on the lawn. And, i re-powered the tractor, and sold it. Did i open up the stuck engine---???---Heck, no. It'll give up its head, and a few other parts, and then take a ride to the scrap yard! Along with several other ones! It'll be like going on a picnic, with some other engine friends, that are stuck, too!

Ouote: IMO the 8hp Briggs is like the Ford 300 six of the small engine world

For those who aren't old enough, these engines were legendary for lifespan.

There are no short blocks or direct replacement engines for the old 19 cu in flat heads so you might as well tear it down and familiarize yourself with it. As was suggested it may have stuck rings but with no oil the rod is likely seized to the crank. A pipe wrench won't solve that problem.
Muriatic acid and scotch brite will clean aluminum deposits off the journal. Use a micrometer to check for out of round.

this was a very common engine with aluminum bore and synchro-balance. The "type" number is needed to identify the crankshaft. Most crankshafts were the 1' diameter X 3 5/32" extension with the 7/16" bolt hole and a keyway.

397815 or 397816 were common short blocks for these. You will not likely find a short block.

If the existing engine cannot be repaired, check the larger mower shops to see if they have a boneyard with a core engine.

IMO unless the BLock has hole in it or the piston is broke it could be repairable. Most likely the cylinder walls are scored, But, it maybe honeable. If you have to have it. then there is no limit to making another engine work. This includes V-twins, singles or sbc if you have access to a welder, cutting torch and metal fabrication. So If you have time and deep pockets that tractor will run again one way or the other!

90% of the time this Engine can be Resurrected , definite small engine experience and $$$ for parts and rebuilding will be required not impossible but potentially frustrating for a Rookie ! Donor Engine would be the quick fix , but a Short Block Conversion may be feasible . But as Rusty has advised not for the feeble of Heart lol .

I've never heard of checking valve timing other than by marks. Valves that are controlled by a chain or belt can jump, but valves controlled by gears don't jump unless something is severely worn out or broken.

I found an article covering "valve overlap" at TDC on the exhaust stroke.
The degree of valve overlap varies by engine design and is not a constant standard that can be applied to all engines.

The statement: "the exhaust and intake valves will be open the same amount at TDC on the exhaust stroke" might or not be true (regarding this 19 cu in Briggs L-head).
I have not ever seen Briggs publish any valve train specs on their engines (other than cam lobe diameter)) so there is not an easy way to find out exactly "when" each valve opens and closes in the 4-stroke cycle for a specific Briggs engine.

You need to start somewhere in finding out why this engine is seized.
Begin by removing the cylinder head.
Once the head is off, you will (hopefully) be able to see whether the engine is seized at the piston/cylinder by rust and corrosion, which would mean the engine had been stored in very damp (or WET) conditions for a long time.
OR.............if the piston has seized to the cylinder because of overheat (cooling air flow from fan obstructed, or run low of oil).)
If the piston happens to be at BDC when you take off the head, so much the better as far as being able to see the cylinder walls (and any damage there).
The way to determine whether the crankshaft or the piston is what is locking up the engine is as follows.
Does the flywheel (and thus the crankshaft) move even a little bit in either direction?
If you can sort of "rock the flywheel" back and forth with your hands, the piston is most likely what has seized.
If you can't feel even the slightest movement of the flywheel when you rock it by hand, the crankshaft has probably seized to the connecting rod journal, or in the main journals, or both. It's also possible the engine could be seized at all 3 places (in that having 1 defect does not rule out having more defects).
If, while the head is off, you can in fact rock the flywheel a bit, and you can also detect movement in the piston, this could indicate the camshaft is seized.

So, get that head off and begin your search there.

Here is a link that might be useful: Valve overlap

You guys have answered one of my original questions: "Is the engine a total loss, or could it be somewhere between marginal and fixable?" The answer is yes. It�s junk, it can be fixed with enough money and effort, and there�s not much wrong with it. It�s a matter of how I want to spend my money and my time. I will pull the head first, then the sump, and analyze the situation. And post the results. If an overhaul is called for, the engine will stay at the end of the bench until I am ready for it. In the meantime, a donor engine of similar displacement and physical size is not a problem. The valve timing question came up while I was working on another engine that was firing through the exhaust. Someone stated that more than once they had encountered an engine that had been assembled (by a rookie) with crank and cam out of time. There is no apparent reason to open the crankcase on that engine except to check the timing marks. Seems like a waste of time and money to me if there is another way. I guess I will have to become the expert on that one. Get back to you later. I am grateful for all the good answers and opinions and suggestions. You can�t get experience off of the shelf, but you can borrow some from other people. One more thing, to whom it may concern, please remove my name from that list of faint-hearted types! Hey, rustyj, my birthday is September 13. So I am one day smarter than you.

Well, that may be true, but-----time will tell. I think, when you finally realise that the info we all gave you was correct, that you will have the courtesy to admit it to us!
We're waiting----
by: S.A. Rusty Jones

Hello, Rusty -- The info all you guys gave me was correct.

Bth: Did not mean to infer you were faint of heart but rather the Reality of the Work Involved would be Daunting within Time Frame and Economics.... If You have the Ability (Technical and Financially) and Tools and Time You Fluid Baby lol .

I get it. Time and money. Nothing new here. Thanks for the cautionary messages -- I know you guys are trying to help someone out. You are sharing your experience with me, and that is what I am asking for. I intend to learn these engines from the inside out, and I appreciate the advice. All of it, including the bits that don't work for my particular situation.