About 45 years ago, before I was bitten by the "buy American" bug, I bought a 1970 Toyota Corona, with about 150k miles. It was ready for a major tune-up, and I noticed there was only 1 screw (and 1 empty) hole holding the choke plate in place. Didn't hear any strange racket, so drove about another 50k miles, and then rebuilt the engine. Number 3 piston top had a perfect indentation of a choke plate screw. Evidently, the screw made it through both intake and exhaust valves; at any rate, it was no longer in the engine.
If it were mine, I would TRY:
(1) Installing a new bag in the shop vacuum
(2) Gently rotating the engine by hand until a piston was at top dead center
(3) Remove the spark plug from that cylinder
(4) Put the adapter on the vacuum that allows it into tight places, and go through the spark plug hole.
(5) Replace the spark plug
(6) Repeat 2 through 5 five more times
(7) Check the vacuum bag.
No guarantee, but what I would try.
Jon.
