Spark plug

[1956-400]

I'm in high school and I just bought a 1956 400 gas tractor. Got it home last night. It seems to start, run, and drive pretty good. I pulled the number one spark plug. It's a Autolite 3116 and it looks like this. How does it look to you? I know nothing about tractors or engines. Yes, i only pulled 1 plug in the dark yard last night. I'll get to the rest later today.
Thanks you

 

[DanielW]

The 'business end' looks pretty dang good to me - looks like it's burning at about the right temp and with no significant oil/soot deposit. A smidge more carbon starting to build up than a brand new engine might have, but still better than 90% of old tractors out there being used every day. And that slight build-up could very likely just be because it doesn't get worked as hot as it might have been back in the day: That's the case for a lot of old tractors. Back when they were built it was anticipated they'd get the holy heck worked out of them. Not uncommon to work some tractors back in the day so hot that you could see the exhaust manifold glowing a dull red at night. These days most folks don't use their old iron nearly that hard, so the plugs/heads run a little colder than what the manufacturer might have anticipated. With any of my older tractors only seeing light use (usually raking, mowing, pulling wagons) I often put new plugs in one or two heat ranges hotter than the original spec. for that reason. But yours look good enough that I wouldn't worry about that.

I do notice the oily threads on the outside. If I had to guess, I'd say yours is like many old tractors where the valve cover gasket has some small, hardly-noticeable leak or blowby and the plug area on the outside of the engine is a little oily/gunky because of it.

Good luck with your tractor! You've picked a good model to start with, and a good site to ask advice from.

 

[1956-400]

My cousin took out all 4 plugs. This is what they look like. He also sent along a heat range chart for Autolite plugs. I took out 3116, should I replace with 388 s? Stay with the same plug. change brands or just put these back in? I relly don't understand about heat ranges.
Thank you

 

[Duner Wi]

IMO plugs look OK .Save your money for now. I see nothing to be concerned about as we don't know prior use up to there removal.

 

[DanielW]

I'm with Duner: Plugs look good to me. I'd keep running them - save your money for fluid changes and other maintenance/tune-up/repair.

Regarding heat-ranges: The 'heat range' refers to how fast a plug dissipates heat. A hotter heat-range plug dissipates/conducts heat to the head slower, so the plug itself will be hotter and burn off oil/carbon/fuel easier. But you don't want to run hotter than necessary and cook/crack the electrode/ceramic. Those plugs don't look too new, but still look quite good. So if they look that good after (presumably) being in there for at least a few years, I'd think the plug spec and heat-range is good.

Share some pics and videos if you have a chance. Folks on here love to see other folks' new iron. And always good to hear of a younger generation working on old tractors.

 

[John Saeli]

My cousin took out all 4 plugs. This is what they look like. He also sent along a heat range chart for Autolite plugs. I took out 3116, should I replace with 388 s? Stay with the same plug. change brands or just put these back in? I relly don't understand about heat ranges.
Thank you

The Autolite 3116 is the only plug I recommend for your tractor. It is a Non-Resistor, Extended Tip. The 388 is a resistor plug, regular tip for use where there are radios, ect. The less resistance the better. Check your wires to be sure they are Copper Core and not "Resistor" wires. If they say "Carbon Core", or "Resistor", replace them. As nice as those plugs are burning, my guess is that you have Copper Core wires already.

 

[tomturkey]

Love all three of my CASE 400's 2gas 1 diesel. Gonna see if I can wake up Mr. Diesel from its long winters slumber in the next few days. gobble

 

[rustred]

My cousin took out all 4 plugs. This is what they look like. He also sent along a heat range chart for Autolite plugs. I took out 3116, should I replace with 388 s? Stay with the same plug. change brands or just put these back in? I relly don't understand about heat ranges.
Thank you

Good idea to do a compression test also. Number 3 looks more fouled. The others look pretty good. Heat ranges ,… the harder the tractor gets worked the colder the plug u use. The lighter stop and starts you need a hotter plug. That’s one of my favorite cases , the 400. Post a pic of it.

 

[LPakiz]

I had a 400 for 20 years or more. Down pressure on the Eagle Hitch, live PTO and live hydraulics.
I added an aftermarket power steering unit.
Toughest tractor out there, bar none!