Packard Forum Index » V-8 (1955-56)

I tried to find a thread on spark plugs and point sets for the 56 Pats, but no luck. I started getting what I believe is detonation.
Question, Packard manual recommends Champion N-18 plugs. The plugs that were (and still are) installed in my Pat are Auto lite 57's. The car also came with new still in box set of 8 Champion H-14Y and Champion N-16YC. What seems to work the best for standard service use.
I also have 3 sets of points, one set is Delco-Remy 1918148,one set stamped Sorensen DR-13 and a set stamped with AL but no P/N. All three look almost identical. I did not find any of the numbers in my Packard Manual.

Check the ignition timing. Also check for a lean fuel delivery problem. I prefer the AL or Delco plugs over Champion. In fact, i just won't run a Champion plug if trouble is suspected nor on a new tunes up.

Preignition can also be due to gas formulation variations from supplier to supplier and even week by week. I've found that the E85 is the worst. SUPPOSEDLY Marathon is not E85. i NOW HAVE much better results from the Marathon than the Shell V power.

So try a different brand of gas first and check timing. The look for a lean fule delivery problem.

You have two or three different spark plugs and extreme care should be exercised in how they are used.

Talking only about the Champion brand, the H type plugs (as well as the J type) have shorter threads than the N type plugs. There is a difference in length between the J and H types, but I do not remember which one is longer. This is also true for Autolite and AC spark plugs, but they have their own identification numbers.

Using an H, J, or N type spark plug depends upon the size of the spark plug hole. Not the diameter, but the length. All of these spark plugs are 14mm. I believe the Packard V-8s used J type in 1955 and N type in 1956, but I am not certain.

Long threaded plugs (N type) in short holes designed for H or J type plugs may result in the piston hitting the spark plug, and certainly there will be carbon build up on the exposed spark plug threads in the combustion chambers. Many times these plugs cannot be removed without destroying the threads in the heads.

Short threaded plugs (H and J types) in long holes for the N type will result in carbon build up in the exposed threads in spark plug holes, and the proper longer threaded spark plugs may not be able to be fitted because of the carbon build up in the hole threads.

Check carefully to see which spark plug type should be used. Then there are other considerations: heat range, projected or non-projected type, and resistor or non-resistor. This does not even get into multiple electrode types, and or course the Platinum spark plugs.

Not simple, but not difficult to figure out.

Also if you look in the parts X-Ref here there are a few different recommended modern plugs listed.

Packardv8, I agree with your idea about the fuel. Just prior to this problem I was using reg 87 unleaded fuel and it seemed to be running okay except I had some hesitation on acceleration so I put in 5 gallons of 89 octane and also added some octane booster to see if that would help. I was going to retime the engine but first I wanted to make sure the plugs,wires and points were correct. The Auto lite 57 plugs have been working fine so I'll retime using them to see if I can get rid of the detonation issue. I did a dry compression (got 150# +/- 3 to 4#)in all cylinders,and vacuum test of 22inches. So that seems to indicate the internals are okay.

JW, The Packard manual calls for Champion N-18 for the 56. I don't have a N-18 plug to check it against the others as to whether it is extended or not. I went online but couldn't find any information on the N-18 plug, but I'll keep trying. There has to be a cross refrence somewhere.

Bowman, I believe the N-18 is not an extended plug. Champion used a "Y" suffix to denote extended core spark plugs. An N-18 would be a hotter range plug than a N-16. I think AC used an "S" suffix to denote extended core plugs. I do not know what Autolite used. At least that's the way it was ...

The Delco 1918148 points are the original equipment for 1955-56 Packards and correspond to Packard part # 530943. Used widely for many GM vehicles as well.

That same point set fits the sixes with Delco distributors according to the NAPA catalog.

Everyone, Thanks for the much appreciated info. Now that I Know I have the correct point set I can pull the distributor tomorrow, give it a look see, check what I can,(using the Packard manual as guide) fix what I can, install the new points, re-install the distributor and see if I can finally get the timing right, which should permit me to correct the carb issues, idle, hesitation, etc.

I use an NGK BP4ES 6928 non-resistor spark plug. If you are running the Delco D-403 rotor it has the resistor built in. I run straight Delco 440 wiring. NGK was the only non-resistor plug I could find as the originals were non-resistor. N-18s are very hard to find. I bought 10 in a pack years ago just to verify the length, but I never used them. I used to run AC plugs but they are now difficult to find.