AC Delco Spark Plugs

[Doug Meloan]

Needing to know factory correct spark plug for 1963 Cadillac.  I assume it is either the AC-44 or AC-45 spark plug with the green rings but can someone let me know if this is correct and if so which one?  Thanks, Doug

[Jason Edge]

Doug, It will be good to see you and the 63 in June!

[Doug Meloan]

Thank you for all the responses.  I ended up putting R45's in as they were readily available at the local NAPA store and fairly inexpensive.  Car is purring like a kitten so I will run them for a while and then pull them to check the burn color. Trying to get everything in top shape to hopefully avoid any issues when we drive it to the  CLC Grand National in June (1400 mile round trip). I have owned this car for nearly 25 years, but the furthest I have ever taken it was on a 500 mile round trip to Branson, MO about 8 years ago.  Still debating whether to drive our 1971 Coupe deVille or the1963 to the CLC, but really want to bring the 1963.   

[Jason Edge]

Doug, If you missed it be sure to check out John Washburn's Article on AC Spark Plugs in the Sept 2013 Self Starter.  I was trying to find another article he did on another subject and found that piece. Jason.

[Jason Edge]

If looking to stay original the R44 (resistor plug with part # 556 9993) was used with cars equipped with am/fm.

[William Cameron]

your post on spark plugs could be a good addition for "Help Topics" 

[David Thomas]

The AC 44 was the factory recommended plug for all around use. The 45 was an optional one step hotter and the 43 is optional one step cooler. You would use the hotter plug for low speed city driving IF there was a fouling issue with the standard plug, on the other end; you use the cooler plug for continuous high speed IF the standard plug ran too hot.