What spark plugs are you using ??

[moparfever]

So what spark plugs are you using in your 1970 340 4 barrel ?
The service manual lists N9Y while Champion lists N12YC ??
Isn't the N12YC to hot of a spark plug ?

 

[Orangedog70]

How big is the 4 barrel? Stock? Even though I have a big block(440+.30) I use Autolite plugs, I have tried a bunch of other brands, I like the Autolites the best.

 

[moparfever]

Stock 4 barrel.

 

[Orangedog70]

I run a ton of gas, but, Autolites seem to hold up better than the rest, make sure to double check the gap before installing them.

 

[bc3j]

I run Champion RJ12YC in my N code 383 stock motor. Runs good.

 

[Tim Lynch]

So what spark plugs are you using in your 1970 340 4 barrel ?
The service manual lists N9Y while Champion lists N12YC ??
Isn't the N12YC to hot of a spark plug ?

N9Y is what I’ve used in my 340s unless racing then I use a colder plug at the track N8Y or N7Y . Autolite equivalent works good to .

 

[Steve340]

You are right an N12 is hotter than an N9.
I ran N9Y in my 340 with the stock irons heads for years with no problems.
I believe it is safer for the engine to use the standard heat range plug.
Too cold a plug it fouls. Too hot and you may get an extra hole in the piston you do not need.

 

[gzig5]

NGK. I think the GR4.