Electrical: R series spark plugs

[Hawklover]

So I am hopeful I can get the answer to the following:
What is the difference between Champion UJ-12Y and Champion J-12Y?

[Bud]

The Champion UJ-12Y is a really old plug that was produced in the mid to late 60's. It has an internal spark gap that was supposed to improve the spark which I have trouble thinking it did. Even the J-12Y is an obsolete number. I would have to check my Champion spark plug catalog to see what the new designation is. Anyway if you have UJ-12Y plugs they will work fine in an R engine. Bud

[Alan]

The J12Y's were same as AC 44S, Autolite A42, Bosch W145T6, KLG FS55P, Lodge CANY, NGK BP6, Mopar P-3-5P, Napa X505, Prestolite 1442, Texaco 4A-8S.

[Hawklover]

The J12Y's were same as AC 44S, Autolite A42, Bosch W145T6, KLG FS55P, Lodge CANY, NGK BP6, Mopar P-3-5P, Napa X505, Prestolite 1442, Texaco 4A-8S.

Yes, but what is the specific difference between the UJ-12Y and the J-12Y??

[Alan]

The J is a projected tip. and the UJ has the tip recessed down in the shell and the electrode that the spark jumps to is flush to the end of the shell, it was thought that the extended tip would get hot and cause pre ignition.

[studediesel]

https://www.championautoparts.com/Technical/Tech-Tips/decoding-champion-spark-plugs.html

[Mike Van Veghten]

Yes, but what is the specific difference between the UJ-12Y and the J-12Y??

Hawk -

Did you read Buds comment (right after your question) ?
Along with the big poster above.

Mike

[Hawklover]

Hawk -

Did you read Buds comment (right after your question) ?
Along with the big poster above.

Mike

Mike only thing I can see is that the UJ is a "booster plug, if I am incorrect tell me, its ok I have a very thick mid 70s skin;-) .......also it would seem "J" is a non resistor plug.

[Bud]

The U series plugs have an internal spark gap in them and a UJ12Y has the internal gap. A J12Y is a non resistor plug and an RJ12Y has an internal resistor meant to reduce ignition noise. The R added to both Champion and AC plug numbers means that they have an internal resistor inside of the porcelain part of the plug. Bud