In any case , siezed or not , it should be dismantled and rebuilt.
The TV shows of finding a car in a barn , putting petrol in a starting it are just … TV stuff.
If it’s is siezed, one can leave the cylinders soaking with something like penetrine
AS a last resort I suppose you could fill the bores with Caustic soda and dissolve the pistons .
The value in any of these engines is in the basics NOne would be considered a reliable use-able item un-rebuilt.
Being a 3 1/2 litre the crank alone is a certain value,as is the block , The carbies are the original tall top type- nice.
Then there is the car it’s sitting in , Even if not restorable, it would still have a lot of useful parts.
And being a MK IV it will have alloy conrods , not something I would want to drive overly far on
I can’t see that turning the engine over , or not would markedly change the value
In fact if it’s going to affect the price , you would be better to convince the seller it’s siezed , get it cheaper and still have to do a similar amount of work to get it running .
I suppose if you want to check whether it turns, you could take outthe spark plugs, put some oil i the holes and try to turn it by the large nut on the front of the crankshaft.with a large spanner.
If the engine is located in a Northern zone subject to freezing, try to visually check the freeze plugs and engine block for possible signs of damage while sitting. At worse, depending on price, many valuable parts can be salvaged.
Popop
Plus I see its a Left Hand Drive, so there will be useful parts on the clutch and brake systems. As I recall Ed was working on a lefty and wanting some info.
Squirt some oil down the spark plug holes and leave it sit awhile. Try the cranking handle, or a 1-5/16" or 33mm socket and extension with a long handle, turning in the tightening direction, and if it doesn’t turn, negotiate for the whole car on that basis.
Make a note of the chassis number and other data plate info for saloondata.com
I see it is still fitted to the car. Does the car roll? If it does roll, stick in top gear and try to push it forward. This will turn an in-seized engine. If it doesn’t roll, have you tried a set of booster cables or a battery to give the starter a try. Assume seized and negotiate accordingly.
May not be practical in your case , but they say boiling oil in the cylinders works well on a seized Engine
If it was me , I would take the plugs out , poor a little fuel mixed with oil in the cylinders , then turn it slowly with the starting handle , your soon see if its seized ,if it was seized that would not put me off from buying it , engines like that are getting hard to come by !!
If this is part of the negotiations for purchase, then you probably don’t want to be able to turn it over. I would put minimal effort into it, say it’s totally rusted solid and negotiate downwards. Then when you get it home you can spend all the time in the world gently freeing it up.
I’ve had better luck hooking up a small water heater and circulating pump to a seized block.
Fill the bores with your original recipe of oil/penetrant/secret ingredient and let the hot water circulate.
Turn the water heater on and off with a water heater timer.
The thermal cycling on the block does wonders when you realize you are heating up the block as a whole giving you some extra clearance along with allowing the bores to expand just a bit to flow the penetrant solution.