Measure piston stroke?

[Illusion01]

I have a question. Is it possible to find out the what stroke a crankshaft has, while it is mounted on an engine, without taking the whole engine apart?

Our idea is as follows:
To simply remove the spark plugs, then turn the engine manually on the bolt on the crank pulley (is that what its called, the place you can manually spin the engine?). And then measure the highest position/place the piston is in and after some spinning the lowest position it is in, doesnt this measurement tell you the piston stroke, and thus also the stroke of the crankshaft? And you should be able to double check on the other pistons.
Does this make sense?


The car and engine in question is a classic Saab 900 2.1l, B212i -93



A little more history about the car for the interested:
We know from the previous owner, that his mechanic restored the engine (many years ago), replacing among other things the cylinder head and he said they used one from a Saab 9000 2.3l if we recall.
Since the car was working fine atm, we didnt think about it much more at the time. However a few years later we had some troubles and we took apart the engine as well and we had bought a new crankshaft for the car. But when we were going to mount the new crank we concluded it wasnt the same as the one in the car (we recall it as having a different stroke length). Therefore we could not mount the new crank, instead we were forced to take out the original and have leave to a workshop who "grinded" it (dont know if this is the right word, but when they polish it enough to fit new higher-dimension bearings).

Since then, after we put the engine together I have been measuring the crank bought and it has 78mm stroke, which is suppose to fit, leading us to believe previous owner might of changed the crank as well, and since the crank from Saab 9000 2.3l has 90mm stroke, that would explain why we concluded the new one didnt fit.
I know it sounds unlikely but we know he was a Saab mechanic and he had been doing major work to the engine so thats why we suspect this... and we would really like to know once and for all, what crank is in this car, to find out if we simply remember it wrong and that it was something else that leaded us to believe it didnt fit or that he actually changed it.
The crank we bought is measured to be 78mm and also the Saab nr on it indicate it should fit any B202/B212. So here's our little mystery.
However, since the car has been working great since we put it together again, we really dont wanna take it apart.

Thanks for any help/suggestions
Also sorry for bad english

[DrewP]

Yes, you can measure it that way. A long socket extension dropped down the spark plug hole works well.

If the car is a manual transmission I usually find it's easier to spin the engine from the flywheel, even easier than that is put it in gear with the brake off and 'bump' the car forward repeatedly to turn the engine.

Your English is fine, no need to apologize! And welcome!