Green markings on AC spark plugs

[Mike M.]

have several sets of AC 44 plugs , been with me since dirt was young. can't remember if the 4 green lines in the porcelain are equal in width or the green band closest to the wire end of the plug is wider than its three brothers closest to the electrode end of the plug. i have both types and am installing them in my 57 250 hp engine.all this pertains to vintage 1957 ac delco plugs.mike

[Bill I.]

Re: Green markings on AC spark plugs

There were 2 ways Mike. The earlier ones had 4 equal markings. Later, say 1970, they changed to 3 fine lines and 1 wider one at the wire end of the plug. Bill.

[Mike M.]

Re: Green markings on AC spark plugs

thanks bill. 4 skinny green bands ones get the call. mike

[Roy B.]

Re: Green markings on AC spark plugs

[John D.]

Re: Green markings on AC spark plugs

have several sets of AC 44 plugs , been with me since dirt was young. can't remember if the 4 green lines in the porcelain are equal in width or the green band closest to the wire end of the plug is wider than its three brothers closest to the electrode end of the plug. i have both types and am installing them in my 57 250 hp engine.all this pertains to vintage 1957 ac delco plugs.mike

Doc, I see u r having a sr. moment. Happens to the best of us. I lost a customers 810 baseplate yesterday. Looked and looked. Couldn't find it no how and was hitting the panic button.
So I went out for nice Chinese lunch and came back and wouldn't you know the tooth fairy put in on top of the workbench. It only gets worse. JD

[Vinnie P.]

Re: Green markings on AC spark plugs

Only 250 hp???? Did you ever own a Corvette you restored with ONLY 250 hp? (real hp)...so what's the real hp? Can fool some of the people etc....

[Dick W.]

Re: Green markings on AC spark plugs

Vinnie, NOS, dry ice, boring bars, long arm cranks, four bolt blocks with 548 casting #'s, amazing what a little of the "beast" can do in Western Maryland

[Mike M.]

Re: Green markings on AC spark plugs

vinnie and dickie_how dare you two question my restoration efforts. when i dyno'd the 283, it made 253 HP so i disassembled it and installed a pair of head gaskets. mikie

[Gary C.]

Re: Green markings on AC spark plugs

Mike, me thinks the green stripes didn't start until 1960. Here's photo of a NOS box of 1958 AC46 plugs on the right and 1960 AC46 plugs on the left. Attached is a copy of the Chevy Technical Service Bulletin that shows the change in '57 from AC44's to AC46's. Gary....

[Roy B.]

Re: Green markings on AC spark plugs

Gary!
So did plugs having those ridges with no green lines start in 58 and 57 dint have any ridges .
My 57 FI 250hp dint have those ridges

[Gary C.]

Re: Green markings on AC spark plugs

Roy, have a couple of passenger car engines in the back of my heavy metal pile. They are Oct & Nov 283's. Both cars were wrecked in early '57 with less than 5k miles on each of them. They both have the 4 plain ribs and only the green AC. Bought these engines in the early 70's out of a wrecking yard. So, that what I've always based my conclusion on. Sorry, can't say for sure whether Corvettes in 56 & 57 left the factory with ribs or without. Am looking for some NOS '56 & '57 plugs, but so far no joy. Thanks for your info. Gary....

[Vinnie P.]

Re: Green markings on AC spark plugs

vinnie and dickie_how dare you two question my restoration efforts. when i dyno'd the 283, it made 253 HP so i disassembled it and installed a pair of head gaskets. mikie

Yeah...at 50% power

[Ian G.]

Re: Green markings on AC spark plugs

here's some info I was able to glean from TDB posts and my own investigation:

Type 1 AC plug (53-57) no green bands and lacks circular ridges on the ceramic tower.
Type 2 AC
Type 3 AC plug (60-74) 4 thin green bands over circular ridges on ceramic tower.
Type 4 AC plug (75-?) three thin and one thick band on top of circular ridges.


I came up with the 74/75 years because I inquired about some plugs and a box that was marked 1974 had the 4 thin lines, while one marked 1975 had the three thin and one thick... What do you think?

[Mike M.]

Re: Green markings on AC spark plugs

never got into spark plugs but it would seem the 55 model year was last for no ridges on the porcelain. however, when it comes to plugs(spark, not chewing) , i'm a rookie. mike

[Joel F.]

Re: Green markings on AC spark plugs

when it comes to plugs(spark, not chewing) , i'm a rookie. mike

What is your brand? Aren't you an MD?

I enjoyed the el cheapo Xmas story by the way.