How many's a few?

Four or five!

I guess if you've had the starter motor & cylinder heads off and there's nothing else physically stopping it turning, there's ony one thing for it!! You say the valves look fine, but will they actually open? If you can't turn the flywheel, there's no way of knowing I suppose.

imo,
That business with loose carbon or other debris in the cylinder, which can prevent an engine from turning over following a long period of storage, won't be a problem once the engine has been successfully started and run, even if only for a few minutes...

Also, the chances of the starter motor managing to engage with the flywheel ring gear at anything above a fast idle are next to zero

Unfortunately, the odds seem to be on a more serious problem with this engine.

Just how high did the revs go under a condition of no load and for how long?

Ken

p.s. Now that the starter motor is out of the way, is it possible to get a screwdriver in position to lever the flywheel round?
Don't use excessive force, just enough to determine how far the crank will turn in each direction.

Hmm! I see....I saw the engine running before I bought it and was running round town in it for three days!


OH Dear! The revs went higher than I've ever reved! only for a few seconds then again for a fraction of a second!:(


Yes I've done this! only a couple of notches actually!

Hmm.. 2 bent exhaust valves methinks....

stab in the dark, but if the engines actually siezied (as in pistons) then rock flywheel back and forth gently and not excesivly

you could do this by releasing tension on alternator belt, and using a 14mm socket (right size?) on the bolt that holds the fan on? not sure if that will work but as i said stab in the dark!

hope you get it sorted

Don't James!... one day something in the dark may stab back!

I've never trashed an engine that badly (not an a series anyway) but assuming the valves have made contact with pistons, and bent, what parts will be needed? I assume pistons and heads, or is it possible it's only the valves? I might sound like a dumbshit but I have a few engines in bits here and if I can, I'll post the bits up.

Iirc, ( if not, hope Roy will correct me )
on those occasions when a race engine had been 'buzzed' high enough to bend an exhaust valve, more often than not fitting a replacement valve was all that was needed.

( Mind you, that was in the good old days when camshafts with the original profile were in use.
Nowadays, the shopping bill would be considerably longer... )

What I don't understand about imo's engine is why the crank won't rotate more than a few teeth, which is why I suspect something more deeply rooted is amiss.

ken