Packard Forum Index » Pre-War (1899-1942)

I recently purchased a 1938 1601-D and all of the information indicates that 10 mm spark plugs are used with this model. The plugs that are in the vehicle are 14 mm. Were certain 38's equipped with heads that were tapped for 14 mm plugs, or is it more likely that the head was swapped with a different model?
Any idea as to what the right plug would be to use. There are currently Champion UJ 12Y plugs in the car.
Thanks for any info you may be able to supply.

Packard kept with 10mm plugs until partway thru the 23rd series (1949/50), as did Buick and a few others. They may have later offered service heads for your car in 14mm, I don't recall but others will no doubt comment, in any case the answer should be in the parts list or service letters which are available to you here.

However, many the corner gas stations made nice money doing conversions to 14mm. Easy to tell if your head is off if you were so converted. Since the 14mm have a greater depth of thread, if converted a few turns of plug threads will protrude into the combustion chamber when the plug is installed. These tend to fill with carbon and sometimes make plug removal problematic.

Autolite 306 is a suitable 14mm plug and available at any good local parts store.

G'day Oldrookie,
to PackardInfo, and I invite you to include your '38 1601-D in the Packard Owner's Registry.

Just found a number on the head. "Stamped" in 5/16" numerals - 0341006 on the front top of the head. I haven't been able to find anything with that number. It appears to be a cast iron head.

341006 is a casting number which is often one digit different than the part number

Part number341005 is the standard compression cylinder head for 1935-36 120 models with 14 mm spark plugs

Thanks for all the info! Sure explains a lot!