Spark plug cross reference???

[Guest 49 Packard]

Can anyone recommend a suitable cross for my Autolite P-4 plugs? I don't seem to be having much luck.

Whether Autolite or not, these would be the plugs used in a 22nd series 288.

Thanks very much.

[Guest imported_Speedster]

Will the Autolite #308 fit?

See Link: (this website lists the '50 but not the '49)

(mouse-over 'More Info' button for specs)

http://www.sparkplugs.com/results_app.asp?productTypeID=1&AAIA=1435141

[Guest 49 Packard]

No, that's a 14mm and the original is a 10mm. The 23rd series (1950) evidently had two different types at different times.

[Guest imported_Speedster]

Sorry, I went thru a very extensive 'Cross-reference' list and could not find a P-4 listed anywhere. (There are 10mm plugs in the list tho, go to far right side to see size)

Here's the link if you want to check, but I want to warn you it is a very big list and takes awhile to download and search thru.

http://www.angelfire.com/extreme4/skidoolympique/SPARK_PLUG_CROSS_REFERENCE.htm

[Guest imported_48DLX]

I think I used Delco M-8's in my 48 288, not positive, but I think that is what is in there. Seems to run fine.

[Owen_Dyneto]

My 1962 AC conversion chart shows the Autolite P-4 to be equivalent to AC 104 and Champion Y4 and Y5, and the Autolite P-6 to be equivalent to AC M8 and Champion Y6 and Y8. For your Packard, the 1962 recommendation (with the gasoline of that era) was for AC M-8 for light service, and 104 for normal service.

Have you considered just going to the Autolite website and getting a current recommendation? I've had excellent luck with their plugs, and additionally like the fact that the shells are not cadmium or bright-plated which makes their appearance correct for your vintage. One supposed advantage of getting current recommendations is that changes in product and gasoline are taken into consideration. Can't assure you that is true, but that's what one plug manufacturer told me a while back.