Hot Rods 413 Chrysler Spark plug

Hey guys trying to resurrect a 1962 Chrysler 413 engine and they list a 3/8 and a 3/4 reach spark plug for that application. Any ideas on determining which one to use? Came out of a Chrysler 300 with single four barrel. Hoping maybe one of you Mopar guys might know? Thanks

 

Wouldn't it be based off of the thickness of the area its going through?

 

My guess is that the 3/4 is the industrial head, but it's only a guess. What size are the head size 13/16"or 5/8"?

 

Who is "they"?

Should be 3/8

 

"Any ideas on determining which one to use?."
Look in the hole where the plug goes. Are the threads 3/8'' deep or 3/4'' deep ?

 

>>>Who is "they"?>>>

Looks like RockAuto. They have a closeout sale on the 3/4" Champion RN14YC. Only one third the price of the correct 3/8" RJ14YC. Plus he'd get an extra 3/8" of thread with the cheaper plug. How can he pass up a sale like that? 8^) Jack E/NJ

 

3/8's the winner......

 

"They"is always the ones that people think have the answers.

 

Rock-auto explains a lot.
The 3/4" length is a small block plug used in the 318 and maybe a 324.
A 383 and the 413 should be a 3/8" long plug, unless you have some really special heads.
The 3/4 long plugs will screw into the hole, but they won't look very good after the piston smashes them. Gene

 

Gene, not familiar with Rock Auto or Island you refer to? The reason I ask is to keep that from happening. They is referring to the Champion Spark plug website https://www.championautoparts.com/. Would anyone know the OEM spark plug for the application I mentioned earlier? Thanks

 

J12Y maybe?

 

J12Y would be a big block Mopar plug number (383, 400, 413, 426 W and 440).

The "J" is the plug thread style and size, or how it seats in the head, how long the threads are, and the thread size and count.

An "R" in front of the "J" would indicate the plug is a resistor plug, or it has radio noise suppression built into it.

The number "12" is the heat range of the plug, it could be anything between a 9 and an 18, with the 9 being the coldest range, and the 18 being the hottest range. Most big block Mopars use between an 11 and a 13 heat range. A 9 was used primarily for racing purposes and would have been a cold plug that would foul easily in most normal applications, and the 18 would have been a very hot plug used on an extremely used motor with a plug fouling habit to gain more life out of the plugs. The heat range would be determined by how far the electrode and the porcelain around it protrudes into the cylinder more then the thread stop does. The hotter ranges protrude into the cylinders more then the cold plugs.

The "Y" is the material the center electrode is composed of. Some also may have a "C" after the "Y" and that would indicate there is more copper content in the electrode, that became more available as the plug gaps began to increase in the mid - late 70s.

All that means is that a plug number RJ12YC plug will also work in your 413, gaped at .035. Gene

 

Use the 3/4 and get a little compression boost.

 

361, 413 & 426 industrial engines use the 318 style (3/4" reach) plug. They have a weird head and the plug sticks up on an angle. If you have a passenger car engine it will use the 3/8" reach plug. That plug sticks out the side just like a SBC. The older Champion number was J12YC. Or RJ if you want resistor type. And I think Autolite is number 74 or maybe 75. Gene.

 

Thanks fellas. Gene, I wondered why Champion offered both the 3/8 and 3/4 reach for the same application on their website. Appreciate the clarification!