Packard Forum Index » V-8 (1955-56)

Greetings, V8ers,

I just finished building an Autolite distributor with a custom Pertronix electronic ignition for the 364" V8 going into my E12 Studebaker pickup. This was necessary because last I checked, Pertronix did not have a fitment for the Autolite. They do have a bolt-in module for the Delco and I built one of those while I was at it.

In setting up the centrifugal and vacuum advance curves, I had to do a bit of research. I've found three different Autolite numbers and two Delco numbers.

Autolite IBJ4001B, C and D Was there an A?

Delco 1110865 and 1110873

Are there any others?

That there were five differing centrifugal and vacuum advance curves and two different initial timing settings indicates the Packard engineers were working to control pinging with the highest compression ratio in the industry.

Another thing I noticed was the shaft end play was on the high side of the already generous specifications. I shimmed mine back below the minimum. This will improve spark timing accuracy. When the distributor shaft can move up and down, the spiral gear advances and retards the timing.

Any current recommendations on spark plugs for the 374"s? Every time I learn a manufacturers numbering system and heat range system, they change it and discontinue those I recognized. Anyone tried the NGK plugs? Which ones worked for you?

thnx, jack vines

Jack, I run an NGK non-resistor plug BP4ES 6928. I have been running these in my 400 for a couple of years. I put them in the Caribbean and Patrician also. I do run the Delco rotor with a built-in resistor.
They cost me $1.98 each.

JV writes: "Every time I learn a manufacturers numbering system and heat range system, they change it and discontinue those I recognized."

Such an epiphany!!!! Maybe look at some AC Delcos for a change. But then again noone seems to like AC for some reason. I've never been able to figure why. Sure wish someone would tell me.

According to my 1976 AC book:
1956-55 V8 7/16 Reach 43LS.
3/4 reach R45XLS or 45XLS.

The AC numbering system has been very consistant from 1955 thru about 2002 that i know of, maybe even later. IT's real EZ to interpret the numbers, suffixes and prefixes.

This subject never ceases to amaze me.

Also try this:
https://packardinfo.com/xoops/html/modules/parts/searchform.php?PartDesc=spark+plug

However note that the AL or MotorCraft numbers are resistor/nonresistor based on the odd or even first number (double check that).

Amazes me after all these years our forum interchange list still shows the same part numbers for "All '55-56" when the '55 and '56 heads take completely different reach spark plugs.

thnx, jack vines

I checked my maintenance log. My 56 Exec came to me with AL 66 plugs. Most likely came from Kanter since the former owner bought everything from Kanter.

I bought a set of 45XLS at a local autoparts strore some 4 years ago and those are in the car now. Also bought a spare set on eBay later on.

THe 45XLS deciphered:

"4" = 14 mm.
"5" is middle Heat range (3 thru 8(3 is cold 8 is hot )).

"XL" = extra long reach (3/4 for 14mm).

"S" = Extended Tip (except 7/8 threaded plugs).

Maybe use that info to 'build' a number for plugs from your favorite manufacturer.

Note that my AC book indicates a 43LS (heat range 3) for the 55 V8. Seems odd to me that such a rather cool plug would be used except under extreme heat or racing conditions.

The 45XLS (heat range 5) would be about rite for middle temerpature plug.

Autolite is the most commonly available spark plug and they have changed their nomenclature three times in the fifty years I've been buying plugs. Their 56 plug was one which worked well in Packard V8s, but recently it is showing as discontinued and they are trying to substitute the 66, which is a hotter plug

To add to the confusion, with US plugs, as the numbers get larger, the plug heat range gets hotter.

With Bosch and NGK, as the numbers get larger, the heat range gets colder.

Throw in the platinum, platinum-plus, iridium and iridium-platinum plug variations, none of which really apply to our cars and most of what comes up in searches is all over the map. The sparkplug.com site will give heat ranges from #5 to #14 as interchangeable. NOT!

thnx, jack vines

Yes. I got into the AL 66 vs 56 controversy some 3 or 4 years ago. According to the book at a CarQuest auto parts store the 56 is NON resistor and 66 is resistor. I looked at the book at my own hand and my own eye. And yes, the 56's were listed as discontinued.

That's why i went with the AC 45XLS. But those are getting hard to find now. Even on eBay.

BUT, maybe the codes i decipherd above can be used to "build" a more secular number for plugs.

Jack Vines wrote: Quote:

"Back in the day" of H-O Racing, I used to sell an "Accuracy Kit" for the Pontiac HEI distributors, which included custom weights, vacuum advance and shims. Of course, the shims were to minimize the distributor housing to gear end play. I'm glad to hear that you took care of the "spiral gear" timing change problem on your rebuild. FWIW, most seem to overlook that problem.

Craig