Many Fiats (124 series, 1200s, X1/9s) require an aviation–style nut to hold the air cleaner down on top of the carburetor. Often, shops or owners unknowingly replace this special aviation–style nut with a regular nut with washers.

Unfortunately, any nut other than the original equipment one is likely to back itself off the stud due to engine vibration. Once loose, the nut and washers will fall into the carburetor and get swallowed by the engine, potentially causing severe damage. A few lucky ones may get pushed through to the exhaust system where they'll rattle around the muffler.

Tightening the incorrect nut down super-tight won't do the trick. In fact, you may pull the stud right out, creating a new and different problem. The hard plastic on the edge of the O.E. nut is the key.

So if your old one is incorrect, replace it with a new correct one. If yours is correct but loose, take it off and whack it with a hammer on one side, enough so that when you screw it back on you'll have to use a wrench or nut driver to tighten it down to the sleeve (in other words, it needs to be more than hand-tightened but not so tight you pull the stud out).

2. The second part of Chris' Tech Tips which appeared in the premier issue of Ciao!NEWS is our online Tech Tip for April 1998 " The Long & Short of it." All about the correct radiator cap for your Fiat.

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