C1 spark plug trivia

[Roy B.]

I hear a lot of questions on spark plug choices .What heat range to use and what AC number to get, and the original look of the plugs for= high speed or racing. I don't know if the plugs are judges for the condition the Corvette is used for . I never hear any one mention a Commercial plug but they were recommended and installed at dealers for those owners that didn't only use their Corvettes for going out to get a pizza. This started in 57 on all C1's that I know of but could be wrong.
Also on this page is how to tell a C1 correct converter for the year PG you have. if you go looking for one to buy. Can also determine if your looking at a Corvette trans or a trans to but, but for the tail housing. My second post has a pic. of a original AC 43-5 Com. plug. I can seem to put two pic. up at the same time

[Roy B.]

Re: C1 spark plug trivia

How many of these have you seen??

[Clem Z.]

Re: C1 spark plug trivia

back in the early days the "C" plugs were used by corvette racers but they used "RAJAH" terminals on the packard "440" plug wires because the rubber boots would burn off. if you are looking for a odd ball spark plug i have a brand new "edison" spark plug in the box. these plugs are made to be taken apart so you could clean the carbon from them.

[Dave S.]

Re: C1 spark plug trivia/Second question

Roy,
What year were green rings introduced on AC spark plugs??? There was a period of time when AC went from the smooth shanks )like in Roys photo) to a ribbed shank but the ribs were white.

[Roy B.]

Re: C1 I don't know think early58???? *NM*

[Jeffrey S.]

Re: C1 spark plug trivia/Second question

Dave:
Based on Delco ads, ribbed porcelains were introduced in mid to late '55, probably for '56 production. The ribs were plain (no green stripes). Ads for AC sparkplugs beginning in late 1959 showed green stripes. It is very likely that the '60 model year cars came with green stripes. I have copies of ads for almost every year throughout the '50's and '60's as documentation. The unribbed plugs as pictured above were designated "Corolox" although later stock did not have the words written on the plugs. The first ribbed plugs were designated "Hot Tip". The green rings were called "Fire Ring". There was, of course, plenty of overlap out in the field as old suppplies were depleted and new stock brought on line.
Hope this helps.
Jeff

[Jack H.]

According to one source....

Type 1 AC plug (53-57) has no green bands and lacks circular ridges on the ceramic tower.

Type 2 AC plug (58-59) has no green bands but introduced the circular ridges on the ceramic tower.

Type 3 AC plug ('60 & up) has both green bands and ridges with later, service replacement plugs have the top green band thicker/wider than factory originals that had for equally sized, thin green bands.

[Dave S.]

Re: C1 spark plug trivia/Second question

Jeff, Jack, Roy,
Thanks for the detailed information. Based on my AC spark plug collection and studying examples over the years I would have said 1960 was the year of green rings as well. All 1961 dated AC plugs have green rings. Don't have any with 1960 dates but 1959 are definately without the green rings. Sounds like we have solved this question. Thanks guys.

[Roy B.]

Re: According to one source....Jack

Would NCRS except a commercial plug as original ,say if a Corvette was showed as a factory 283 high air box engine.

[Clem Z.]

GMs explanation for the ribs

was they needed a long path on the outside of the porcelain to prevent arc over to the metal shell. could this have happened when they went to resistor plugs?