Correct plug heat range for 360

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smokinnjokin

smokinnjokin

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Greetings all.
I am doing some research and trying to select an appropriate plug for my engine. I have a 360 smog motor in my car, with what I assume is a stock cam (I did not do the swap and have no idea what the engine internals are), edelbrock intake, carb and headers. So basically almost stock. Car came with autolite 64's in it.
I would like to put some NGK's in it, looking at the GR4 or GR5. I generally run 87 octane, and it seems a hotter plug would be appropriate for such a mild, low-compression motor. The FSM isn't much help in this matter with today's poor quality fuel and the different timing specs we are running. What do you guys think?
 
NGK’s are a waste. All those fancy iridium plugs etc. are made for one reason. 100,000 mile plug changes. Other then that they have no advantage. IMHO that is.
 
smokinnjokin said:
Greetings all.
I am doing some research and trying to select an appropriate plug for my engine. I have a 360 smog motor in my car, with what I assume is a stock cam (I did not do the swap and have no idea what the engine internals are), edelbrock intake, carb and headers. So basically almost stock. Car came with autolite 64's in it.
I would like to put some NGK's in it, looking at the GR4 or GR5. I generally run 87 octane, and it seems a hotter plug would be appropriate for such a mild, low-compression motor. The FSM isn't much help in this matter with today's poor quality fuel and the different timing specs we are running. What do you guys think?
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May be 1 step hotter than what is recommended. Champions were stock. Some swear by Autolites and NGK. Your choice. I would look up by application first then Cross reference the original plug number just to be safe.
 
fklskv said:
NGK’s are a waste. All those fancy iridium plugs etc. are made for one reason. 100,000 mile plug changes. Other then that they have no advantage. IMHO that is.
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I don’t see how they are a waste as they cost 1.50 a plug on rockauto, A couple cents more than autolite copper. I agree with you about all the fancy stuff, I just picked them because they were cheap and seemed like a decent set of plugs.
I don’t want to get into up spark plug brand debate, there’s pages of that in the forum already. I was just curious if anyone had some actual experience with spark plugs in a warmed over smog 360 running pump gas.

toolmanmike said:
May be 1 step hotter than what is recommended. Champions were stock. Some swear by Autolites and NGK. Your choice. I would look up by application first then Cross reference the original plug number just to be safe.
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I have no idea what the original application for this motor is, I was kind of thinking along the same lines with the GR4. Or an autolite 65, 66.
 
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318willrun said:
correct. Not sure what year he has, but I'd run RN12YC. 14's may work great as well
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Watch the cold plugs though. They can cause a rough idle/ misfire. I chased that issue around on my 273 for a couple seasons.
 
318willrun said:
RN9YC would be a cooler plug that many would run. 12's are really not considered a cool plug. I consider 14's a hair hot
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The 14's are the stock plug. any plug from a 13 on down would be colder than the factory heat range.
 
I got the car with a 160 degree thermostat and autolite 64's, with a points gap of 0.005". Right now I have autolite 65's, 180 degree thermostat and points back to 0.014" as per fsm. So sounds like I have the right plugs. I will looks into the champions as well, thanks all for the tips.
 
smokinnjokin said:
I don’t see how they are a waste as they cost 1.50 a plug on rockauto, A couple cents more than autolite copper. I agree with you about all the fancy stuff, I just picked them because they were cheap and seemed like a decent set of plugs.
I don’t want to get into up spark plug brand debate, there’s pages of that in the forum already. I was just curious if anyone had some actual experience with spark plugs in a warmed over smog 360 running pump gas.



I have no idea what the original application for this motor is, I was kind of thinking along the same lines with the GR4. Or an autolite 65, 66.
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It's a waste of money because that plug wasn't designed to do what you are asking it to do. Use a copper core plug and be done with it.

I stopped using N series Champion plugs back in the early 90's. Use the C series. Instead of the 13/16 hex the N series uses, the C series uses a 5/8 hex. It's much nicer to use a 5/8 plug socket than that big, clumsy 13/16 socket, especially if you have headers.
 
yellow rose said:
I stopped using N series Champion plugs back in the early 90's. Use the C series. Instead of the 13/16 hex the N series uses, the C series uses a 5/8 hex. It's much nicer to use a 5/8 plug socket than that big, clumsy 13/16 socket, especially if you have headers.
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I've never tried the C series... it's a good thought. I'll have to check that out. Only thing that changes is the socket size?
 
yellow rose said:
It's a waste of money because that plug wasn't designed to do what you are asking it to do. Use a copper core plug and be done with it.

I stopped using N series Champion plugs back in the early 90's. Use the C series. Instead of the 13/16 hex the N series uses, the C series uses a 5/8 hex. It's much nicer to use a 5/8 plug socket than that big, clumsy 13/16 socket, especially if you have headers.
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Is RC14YC the plug you are referring to?
 
What ignition are you using? With the headers and intake an RN12YC gapped to at least .035 would be my choice. As 318willrun noted, 14's are fairly hot plugs, made to stay clean in a cooler chamber temperature EGR engine. My present 9.5-10:1 combination is really happy with an RN11YC-4 gapped to .045, so I'm going to say no hotter than a RN13LYC. RN14s act like an absolute glow plug in my setup.
 
smokinnjokin said:
I got the car with a 160 degree thermostat and autolite 64's, with a points gap of 0.005". Right now I have autolite 65's, 180 degree thermostat and points back to 0.014" as per fsm. So sounds like I have the right plugs. I will looks into the champions as well, thanks all for the tips.
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It's not really about coolant temperatures. It's about combustion temperatures, and more specifically how much of that heat transfers into the plug. The R9Ys were for the higher compression engines (340, maybe 273 HiPO I'd have to look) 12s and 14s are on the lower compression engines. You can start with 12 or its equivalent and then if you see need to keep 'em a bit cleaner, bump up to 14 or equavalent.
 
With no other changes you should be running timing close to stock. If you want better idle, then yes you can bump up initial a little but a lot of stuff is interelated so I'll leave it there. With EGR especially may have to back off the vacuum advance a little to avoid part throttle ping.

Don't see anything to be gained by running a 160 F thermostat. Get oil and coolant up around 190 - 200 F as soon as possible. That gets the oil viscosity in the design range and will burn off moisture.

edit: I'll add it should help the getting the cylinder termperatures up sooner as well. Once the fuel droplets are in the chamber and the valves are closed, within reason, more heat during the compression will help vaporization and make a better burn.
 
Because the OP didn't say what he had for a 360 and what has been done to it I looked up a 1980 360 out of a pick up to find the 14 Champions. Have to start somewhere. I didn't look up whether the 80 had a egr or not. At least I looked it up and didn't just pull a number off the top of my head. "I use a *** in mine but it has more compression or a such and such ignition or headers or the like" doesn't work here. We really don't have a clue what the op has for a 360. The stock plug is the place to start. Pardon me while I look up other 360's to see where the heat ranges go between the years.
 
Garrett Ellison said:
What ignition are you using? With the headers and intake an RN12YC gapped to at least .035 would be my choice. As 318willrun noted, 14's are fairly hot plugs, made to stay clean in a cooler chamber temperature EGR engine. My present 9.5-10:1 combination is really happy with an RN11YC-4 gapped to .045, so I'm going to say no hotter than a RN13LYC. RN14s act like an absolute glow plug in my setup.
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Stock compression for smog motor is listed as 8:1. So it seems unwise to go to a colder plug.

Mattax said:
With no other changes you should be running timing close to stock. If you want better idle, then yes you can bump up initial a little but a lot of stuff is interelated so I'll leave it there. With EGR especially may have to back off the vacuum advance a little to avoid part throttle ping.

Don't see anything to be gained by running a 160 F thermostat. Get oil and coolant up around 190 - 200 F as soon as possible. That gets the oil viscosity in the design range and will burn off moisture.

edit: I'll add it should help the getting the cylinder temperatures up sooner as well. Once the fuel droplets are in the chamber and the valves are closed, within reason, more heat during the compression will help vaporization and make a better burn.
Click to expand...

No EGR, the original smog ports are plugged and I have headers. And I agree with the thermostat. I have no idea why a 160 was in there, maybe a band-aid for overheating at some point. Or perhaps someone just wasn't paying attention and got a generic thermostat at the auto parts store. It runs fine with a 180.
 
toolmanmike said:
Because the OP didn't say what he had for a 360 and what has been done to it I looked up a 1980 360 out of a pick up to find the 14 Champions. Have to start somewhere. I didn't look up whether the 80 had a egr or not. At least I looked it up and didn't just pull a number off the top of my head. "I use a *** in mine but it has more compression or a such and such ignition or headers or the like" doesn't work here. We really don't have a clue what the op has for a 360. The stock plug is the place to start. Pardon me while I look up other 360's to see where the heat ranges go between the years.
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That's what I was thinking putting in autolite 65's, seemed like a reasonable place to start.
 
toolmanmike said:
Pardon me while I look up other 360's to see where the heat ranges go between the years.
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Here's 1973 Dodge, 360 2bbl
upload_2019-8-13_14-18-16.png
 
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