How Do You Date Spark Plugs

[Tom Wesenberg]

At the last swap meet I bought 4 AC spark plugs mainly because they were only a buck each and NOS in the box. They are number 83 SPECIAL, 18 MM thread and 7/8 Hex. I was wondering what time period they were made and what they fit? I know they fit the Model A, but don't know if they are correct for it. The last patent on the AC box is 2,272,338.

What's really unusual is they are sealed in cosmoline, so I'm not sure if I should open one up.

The small Autolite plug is PR-4 10 MM resistor. I know Chevrolet used a small thread for a short period in the 40's, but don't know if this plug would be correct for them.

Plugs change shape on the porcelain every so often, and I'd like to find a chart or pictures to show when these and other plugs might have been made. Does anyone know of a site with such information, or a good book on spark plugs? Thanks.

[Mitch//pa]

did you do a patent search for the time period?

[gwhite]

From my experience, the patent search won't help much...

Sometimes the boxes have printing dates on them...I've got a set of Champions that have 4-41 printed on the boxes.

Another good method is to look at advertising, for instance, Champion advertising shows plugs with brass tops from 1935-41;



The brass top evidently went away by 1942 as evidenced in this ad;



In 1948, advertising shows a different insulator (different ribbing);

[Mitch//pa]

the patent search i did came up with 1935

[Tom Wesenberg]

Mitch, I've never done a patent search, so may have to try it.

gwhite, sure glad you posted those pictures because the second and third Champions are the exact plugs I was trying to research yesterday, and had no luck.

[Roadster62]

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As a rule of thumb anything packed in cosmoline is a WWII surplus item. Bob

[Tom Wesenberg]

Originally Posted by Roadster62

As a rule of thumb anything packed in cosmoline is a WWII surplus item. Bob

That's what I was thinking, as the only things I've seen packed in cosmoline have been for the military.

[700rpm]

I dated a real spark plug in college. She was easy to date: I just asked. Manufactured about 1945, but she still ran hot in 1965.

[emf]

I know I'm new to A's, but 18 mm plugs don't fit my head....

Frank

[steve s]

I understand that you can find any kind of date you want on Craig's List.

[Big John]

emf....i take it, it is not for your head, but for your a's lol Big John

[GrandpasA]

Originally Posted by 700rpm

I dated a real spark plug in college. She was easy to date: I just asked. Manufactured about 1945, but she still ran hot in 1965.

I like your style.. I was thinking on these lines as well when I saw the title to this thread..
I only date hot spark plugs...

[gwhite]

Hey fellas, my apologies for the poor photo of the 1948-up plugs...here is a better one (this from a 1948 Canadian ad);



And a scan from a 1938 Champion catalog (shows the brass top design). Note: 14mm plugs such as the J8 shown below appear to have not used the brass top.



Here's the set of NOS Champion brass tops I picked up for my Winfield-powered "hot rod";

[redmodelt]

Them sparking plugs like live wires! Keeps them feeling young and alive.

[GrandpasA]

Originally Posted by redmodelt

Them sparking plugs like live wires! Keeps them feeling young and alive.

now thats funny and true..

[BILL WILLIAMSON]

Originally Posted by 700rpm

I dated a real spark plug in college. She was easy to date: I just asked. Manufactured about 1945, but she still ran hot in 1965.

Ray, you a dirty old man! And, did this "SPARK PLUG" chick have an expiration date, or does that apply to SPARK PLUGS?
I cooked 2 Lbs of low fat hamburger from Gregg's freezer, dated, 7-29-2010! Cooked a test patty & gave the Dog a bite he smiled & I ate the rest. We had taco/burrito meat for a week, it was DELICIOUS!
Gettin' back to spark plugs, Vermin has like new Champion C-16-C's--Wunder how old they are? Engine was built in '87 & barely run. His 6:00 X 16 Firestones still had nubbies on the tread, but the sidewalls were ROTTEN, but the tubes held air for 3 years
My point is, should we keep our spark plugs & tires & tubes in a FREEZER?
Bill W.

[Tom Wesenberg]

Originally Posted by emf

I know I'm new to A's, but 18 mm plugs don't fit my head....

Frank

You are right emf.

I think I have a loose solder connection in one of my brain cells.

[gwhite]

Originally Posted by emf

I know I'm new to A's, but 18 mm plugs don't fit my head....

Frank

They fit mine (Winfield head)

[19ED30]

Gwhit , is your Fuel Delivery set up a type of Mechanical Injection?

[gwhite]

Originally Posted by 19ED30

Gwhit , is your Fuel Delivery set up a type of Mechanical Injection?

No, it's a early 1930's Winfield SR-B carburetor. The only challenge I have with this combination is getting fuel to it (no fuel pump on the A motor and it's got a '27 roadster body on it, so gravity feed won't work). As my goal was a true period-correct late 30's-early 40's hot rod, I ended up using a hand pump from a '22 Cadillac to pressurize the fuel tank.

Carb;


Hand pump;


Pressure gauge (from a 1918 Dodge);


To maintain pressure in the tank, I needed a non-vented gas cap...I lucked out and found this '22 Cadillac cap; it's got a neat pressure release valve built in (the T-shaped bolt threads into the cap and puts pressure on the steel disc and leather seal);


Sorry for all the non-stock discussion.