Re: Spark Plugs

Posted by Kevin AZ On 2012/5/19 16:11:42

Would someone please "Unconfuse" me!

Machined dome and cast dome spark plugs.

Okay, I went out to the 400 and determined that the part numbers on the heads are "440689" (dang six looked like an eight) because of being thickly painted. So I then go to my Packard parts book and see that under 5.0503 (page 89) "440689" correlates to 5540. Hummm.......but I have a 5587-4182 ....and the SC doesn't get into that ? I'm confused.

So a couple of questions and assumptions....

# 1 -I can assume that I definitely have a machined head which calls for a 7/16" reach plug and not the 3/4" reach that is for 1956 and late production 1955's?

# 2 - What determines late production other than the number in the heads present on the car?

# 3 - Heat ranges - Why are they important to me? These AC 43LS plugs I have on the shelf are at the "cold" end of the chart that Owen provided? Should I care? Hank said in a post that his early production heads had H-10's in them? Will I injure my engine if I don't get this right?


# 4 - In a perfect world, if another one of you guys had a car much like mine ......with it's newly rebuilt engine, 4GC Rochester carburetor, Delco distributor, what would be the best choice for me living here in Arizona at 2300' elevation and warm temperatures most of the year?

Many thanks in advance.