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My 41 120 has piston slap in #4 cylinder. Short of re-boring the cylinder, is there another solution. After the engine warms up the noise disappears. Please advise, and what is a piston skirt expander?

I know they use to talk about knuralizing pistons before. Don't know if they do that anymore.

Old-fashioned remedies for piston slap when finances prohibited a proper rebuild: (1) knurling the skirt on the thrust face to expand the diameter of the skirt, and (2) install a piston expander. Both were capable of providing some short-lived relief, I did both myself many years ago. Plenty of descriptions of needed tools and materials in older editions of service manuals such as Glenn's.

A skirt expander is just that, a spring steel device inserted into the piston from below which exerts an outward, stretching force on the skirt.

If you need illustrations I can provide some from Glenn's Manual.

Never heard of Glenn's Manuals.....

In terms of teaching auto service fundamentals, IMO Glenn's was the gold standard of manuals.

PS - page from Glenn's section on piston service.

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I'd only ever seen Motors and Chilton. Of course now there is Haynes.

OD,
What years does your Glenn's cover?

The covers and front's piece are long gone; the listings of specifications in the back seem to cover the range of 1953 to 1963.

FYI I just checked ebay and found plenty of the manuals to go around.

I have the 1966 version. which there are many for sale on eBay.

I got it from my neighbor in the 70's. Even though it did not list Packard, It did help with basic automotive steps to take. I did not have any Information on my 55 Patrician. Started acquiring Chilton manuals as well until I joined the Packard Club and bought reprints from small world press.