Packard Forum Index » V-8 (1955-56)

Champion N-16Y are in my 320 V-8. These are the long reach with the projected electrode. A photo of them is on my project blog. Recently, I also bought a NOS set off of eBay for a spare.

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Hi everybody:

Here is a cross-reference I found for these motors:

No guarantees on the total accuracy of course.

AUTOLITE 65.

NGK P/N: BP4ES
NGK STK: 6928
Accel: 114
AC Delco: R43XLS
Beck Arnley: 176-9020
Bosch P/N: WR8DC
Bosch STK: 7506
Champion P/N: RN12YC
Champion STK: 404
Denso P/N: W14EP-U
Denso STK: 6010
GM OEM NR: 5613522
Mighty: M4GR42
Mopar: 4091713
Motorcraft P/N: AGS42C
Motorcraft STK: 16
Napa: X562
Splitfire: SF426E
Valley Forge: 33R

NGK TYPE: AUTOM.

Thread size: 14MM
Hex size: 13/16
Reach: 0,75
Seat type: GASKET
Projected tip: YES

THe AC R43XLS should be way too cold of a plug for the PackardV8 or even any engine unless it's running under extreme heat/load conditions. R45XLS should be alot a closer. For rather cold intermittent use of the engine a R46XLS or 47 mite be even better yet.

AS for the other brand of plugs listed it's difficult to determine (maybe except for AL and MotorCraft) because they change their numbering system about as often as i change my socks.

According to my AC spark plug book dated 1976:

55-56 V8 7/16" reach 43LS or 3/4" reach R45XLS or 3/4" 45XLS.

Personal note: on the 43LS listed above i would definately move up at least one heat range to 44LS.

I've fought spark plug heat range problems for DECADES and across a variety of engines!! Here is what i have found:

In order to determine the correct heat range for a spark plug one must first determine the desired heat range in AC DELCO NOMENCLATURE!!! Then if one is so inclined to insist on some other brand of plug cross the desired heat range of the AC into the other desired brand of plug. Then clutch your rosary beeds close to your breast or kneel on your prayer rug or what ever it is that u do and pray for the best. OR just run the AC's and get on with life.

Avoid all of the platinum tipped and gold plated and ivory inlaid and gap less or what ever other hokus-pokus nonsense that the spark plug manufactureres try to promote.

After going back and looking the lady was right (to a point), advance lists the short plugs as being correct for the car, they also list the long ones as bieng correct for the car too.
I'm putting the long ones in but wanted to see if I couldn't clear up any confusion on my part.

Just for those curious ones, they were part # Autolite 437

I've always found this chart from the 1962 AC catalog to be useful, perhaps some of you will want to print it off and save it. Many of the actual plug numbers are no longer valid, though most of the 10mm plug numbers (like M-8) are still current.

For current AutoLite plug numbers I've never been mislead by using the AutoLite website. Its data for Packard goes back to 1899. Select "spark plugs", then "passenger car", and then enter year, make, model and/or engine for a current recommendation. I've used this data regularly and have always found the recommendations to be spot-on.

autolitecatalog.com/Application.aspx?b=A

If you request for a 1955 Clipper, you'll find recommendations for both the 7/16 and 3/4 reach plugs.

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The website additionally offers an overview for antique cars, prior to 1960.


source: www.autolitecatalog.com

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Thanks for the AL website. It's a great resource.
However, the AL web site does NOT give ANY information on HOW TO READ THE HEAT RANGE. (or i couldn;t find any such nomenclature/documentation/instructions/prose/rhyme nor reason in the AL website regarding ANY deciphering of plug characteristics whatsoever in any way shape form or fashion).

Let me put it another way:

If one is handed at random some RANDOM spark plug that is NOT AC Delco then how does one determine CHARATERISTICS of the plug???? I'll even limit it to how does one determine the HEAT RANGE ONLY of the NON AC Delco plug????

I have checked a few Autolite books and they sometimes give very sketchy rules for deciphering the plug number. Sketchy at best. Other brands nearly non-existent info.

Bottom line:
One must be able or have some kind of intructions or decodeing chart or table or SOMETHING to determine the characteristic of the plug that one is physically holding in their hand and viewing with their own eye in real time of the real world.

To the best of my knowledge AC Delco plugs are the only plugs that satisfy the above criteria.

Also note that the AL website crosses 66 into R45XLS and to 45XLS. So the 66 is Autlites answer to BOTH a resistor and a NONresistor plug but does not indicate if the 666 is resistor or not. Again we have an inability to determine from the AL # just exactly what it is or is not.