Did the wing nut on the air filter housing work loose at highway speeds? That happened several times on my Mustang II 4 cylinder engine. It would get a little louder for a few seconds, then “zing” followed by various metallic noises. Kept spare wing nuts in the glovebox, lol. That actually was a decent little engine as far as reliability, hard to kill it as long as the oil was changed and not allowed to get low. Slow and sort of rough, though.
Did the wing nut on the air filter housing work loose at highway speeds?
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My dad fixed that - he replaced it with a lockwasher and a corresponding nut. I had to use a socket to take it off, but it worked. :)