Packard Forum Index » V-8 (1955-56)

Gentlemen,

I purchased a set of AC 43LS spark plugs thinking they would work in my 1955 400. Frankly, it was a chance purchase without prior confirmation.

Can one of you provide me with the application details in which these plugs can be used?

Thanks

Kevin
Tucson

Brrrr, that's a mighty cold plug! According to my 1962 AC catalog its about the equivalent of Champion H-14Y which is also a pretty unpopular number. Only application I saw was 1961-62 Studebaker 6 & 8 cyl.

Thanks Owen,

As I mentioned I pretty much bought those plugs on impluse. Can you please recommend & provide a quick listing of plugs that will work in my Packard V8. If it matters, I have a '55 block that has been rebuilt to '56 374ci standards.

Thank-you.

Kevin
Tucson

R45LS, two steps hotter.

Frankly I'm reluctant to rely on old plug recommendations as the changes in gasoline composition, flame temperature and propogation have changed so much. So I usually take a current recommendation from one of the plug makers. Autolite's site is among the easiest to use, and for my 56 Packard they recommend Autolite 66 for a non-resistor plug (my choice). I've also used Champion RN14YC with good luck. You don't say if your upgrade of a 55 to a 56 V8 involved changing heads but I guess you know there were different plug requirements when they went from machined to cast heads (see Service Counsellors for info). If I still had the 55 heads, I'd hop onto Autolite's site and get their recommendation for 1955.

Kevin, you can go with R45S for short reach, with gasket, or R45XLS for long reach, with gasket. If I remember right, my '55 320 in the Pat takes the long reach, and it's the machined dome, so I'm thinking the Cast Dome heads take the short.

Someone wrote : "Autolite's site is among the easiest to use, and for my 56 Packard they recommend Autolite 66 for a non-resistor plug ...".

I can not find an AL site. HOWEVER, i went to a local CarQuest store and viewed the AL book with my own eyes and at my own hand. it said:
Plugs with a WXYZ numeric code (on the plug) then the last number (Z) is the heat range, 4 cold, 5 mid-temp, 6 HOT. The number, next but one from the last, (Y), indicates RESISTOR/SUPPRESSION. EVEN numbers are resistor/supression (-10 for non-resistor) and odd numbers are NOT resistor/supression (+10 for resistor). The first 2wo numbers (WX) indicate a plug "group family" such as thread, hex size, reach etc.
SO, the 66 is a RESISTOR plug and the 56 is a regular plug. I have seen the 56 and 66 reported as above and in reverse. This has been a major source of confusion for me.
DOES THE AL WEB SITE contradict the above info i have relayed??? I have 66 in my 56 Executive.

According to my 1976 FACTORY AC Delco book, the 55-56 Packard V8 uses 43LS (7/16" reach). R45XLS or 45XLS 3/4" reach. Note that the "R" indicates resistor plug.

It's AC which means This Is Biblical.

I am leaning away from the resistor plugs. I've noticed that my Executive wit hthe AL 66 plugs always had a VERY slight rough idle despite many exhaustive attempts to diagnose it. Running timing at 10 degrees BTDC seemed to help both idle and at high speed. Otherwise the car always started and ran fine in all conditions from -10 degrees F to 103 degrees F.
I'm guessing that the resistor plugs causes the rough idle and occasional low speed slight roughness. SMOOTH as silk at 2500-4200 rpm. Advancing the timing probably compensated for the resistence in the plugs ???????????.

Prior to the advent of resistor type spark plugs and wires, there was a carbon rod built into the rotor - at least in the V8s - for radio noise suppression.

I always felt that resistor plugs with an OE type rotor, and especially with modern resistor type plug wires, might add up to too much resistance.

However, there are rotors out there for an 8-cylinder Declo distributor that do NOT have that carbon rod. Though I do not have any part numbers, I suspect those are from an earlier application as there were significant changes in the design of the Delco distributor for 1957. It would be interesting to see what effect such a rotor might have with your resistor type plugs.