You will if you fill it completely. And also fill the bores via the spark plug holes as I suggested.
Filling it totally will.
I conceed it may leak through some of the seals - although this usually happens with hot thin oil unless they've disappeared. So I'd fill it slowly and check.
I'm talking supermarket oil here at a few quid a gallon - not Mobil 1.
How? You'll just get air trapped under the pistons. The only way you'll fill it completely is to immerse it in an oil bath and turn it upside-down to let the air out, then seal all the breathers etc. If you do that you're likely to get the clutch full of oil too, so it's not worth the trouble.
Incidentally it's worth spraying the flywheel lightly with WD40 on both sides (back via the starter hole) and the starter motor Bendix screw.
You won't get anything much under £3.50 for 4.5l.
You'll guarantee just how a liquid will flow? Besides, even if it does trap air, the rusting properties of that are limited due to no fresh oxygen getting in.
Since it's an unknown engine, the clutch will be unknown too.
That'll do the clutch a lot of good.;-) And WD40's crap at preventing rust
- best to use a proper wax.
I'd call 3.50 a few quid. YMMV.
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