K321 j19lm plug

[Mustang67ford 234]

Working on my k321.  I know it calls for a champion rh10 plug, which is now a champion rh10c plug.  I plan to use an ngk plug whih I believe is a b-6l.  However, when I looked to see what plug was it, I found it to be a champion j19lm.  Looking that plug up, I see nothing where it crosses over to my motor.  Specs seem to be the same as with respect to threads, but it is a heat range of 19 as opposed to 10 and the thread reach is a little less.  Any idea why this plug may have been used or is it a common plug to swap in these motors?  Figured I would check before changing.

[roadapples 6,983]

I'd be changing it...

[Achto 27,571]

1 hour ago, Mustang67ford said:

However, when I looked to see what plug was it, I found it to be a champion j19lm

 

Champion J19LM is the correct plug for a small block Kohler (K141, K161, K181) Chances are that it was installed because that was what a PO had on hand at the time. Champion H10 is the correct plug for a big block Kohler (K241, K301, K321, K341) 

Edited March 12, 2022 by Achto

[RED-Z06 2,221]

Funny you say this, my Magnum 12, started to start a little hard, idled a bit rough, the Correct RH10C Champion only has about 25hrs on it, i put in another, my last RH10C...and it ran better, i put in a J19LM and it actually runs alot better, no idea why...it shouldn't, but it does, im going to push dirt a bit and see how that plug looks.

[squonk 41,109]

A shorter reach will make it run hotter as well. I worked in a garage were the fellow next to me had to install 4 helicoils in the head of a K car. He didn't get the inserts in deep enough. So the plugs were moved away from the combustion chamber. Car came back a month later with 4 melted pistons.

[Mustang67ford 234]

3 hours ago, RED-Z06 said:

Funny you say this, my Magnum 12, started to start a little hard, idled a bit rough, the Correct RH10C Champion only has about 25hrs on it, i put in another, my last RH10C...and it ran better, i put in a J19LM and it actually runs alot better, no idea why...it shouldn't, but it does, im going to push dirt a bit and see how that plug looks.

Mine seemed to run fine as well but didnt really use it before starting the restoration.  Haven't pulled the plug yet as I just started looking into plugs last nite.  I'm interested to see what your experiment produces.

[JoeM 7,874]

I have had several machines come in with the wrong plug and it is hard to believe that would make a difference but is has proven so. I use the Champion or Autolite equivalent.

 

These two plugs will fit but are different reach and heat range. Another thing about heat range is the amount of exposed electrode up inside the plug. That will causes the ignition variation.

 

 

 

Can look the same on the outside but.....much difference. 

[gwest_ca-(File Mod) 11,042]

Never use a plug interchange to select a plug for a given engine. The thread size and length is about all that is common. Even the wrench size can be different.

Use the plug suppliers application chart for a final plug choice. They are the only one's that know the best plug for the application.

[squonk 41,109]

 Also use a recent plug chart. Gas formulations have changed over the years from better to worse. A plug that was spec'd and ran good in 72 may not be the recommended plug today.

[Mustang67ford 234]

On 3/12/2022 at 5:09 AM, gwest_ca said:

Never use a plug interchange to select a plug for a given engine. The thread size and length is about all that is common. Even the wrench size can be different.

Use the plug suppliers application chart for a final plug choice. They are the only one's that know the best plug for the application.

Went with a NGK B-6L which is what is spec'd for the K321 when checking the application guide.  It is also a cross to the chanpion RH10c.