Spark Plug Heat range

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QuickDart360

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Currently have a 360 that has a few mods. Pistons are KB107's for heads 340 Xers and the 292 mopar cam. I have the rn12yc champions in the motor. Sometimes in hot weather or warm dry weather it pings even with 92 pump octane. This is the newer fuel we have. I have tried lately 91 non ethanol gas with a bottle of octane booster from stp. This helps. But my question is would rc9y3 spark plugs be a better choice? To alleviate detonation or ping I get.
 
I’m not a plug expert. Going with just the RN12YC, a step cooler would be the first move I’d make. I don’t know if that number changers to an 11 or what, but I also will be trying this in a day or two or 3….. Having several sudden weirdo issues in the new state.
 
A colder plug should help with pinging ( detonation) ! May need to check your timing also to make sure it’s correct ! Colder plug with cool off faster ! If you get to cold of plug , fowling could become a problem !
 
Champions are easy. Heat range goes cold, lower numeral, to hotter, higher numeral. 10's or 9's?
 
I read in an older thread that the early 340's with the higher compression used rn9yc from the factory. So my 360 has more compression than stock. So I would assume the rc9yc's may be the ticket. I have headers reason for ry's vs rn's.
 
I doubt your plugs are causing pinging, or that colder plugs will fix the problem.

Those are hypereuctectic pistons, right? One of the claims for this alloy is that it runs hotter [ needs larger ring gaps ]; this is supposed to make more HP because more heat is retained in the chamber & this keeps gas pressure high; more 'push' on the piston. But a hotter piston top is also more likely to ignite the mixture before the spark does [ detonation ]. They don't tell you that when you buy the pistons....

My advice is to try & keep the incoming air to the engine as cool as possible:
- cold air induction
- improve cooling system
- block off &/or reduce size of exh xover in the intake
- water injection
- all of the above
 
Bewy said:
I doubt your plugs are causing pinging, or that colder plugs will fix the problem.

Those are hypereuctectic pistons, right? One of the claims for this alloy is that it runs hotter [ needs larger ring gaps ]; this is supposed to make more HP because more heat is retained in the chamber & this keeps gas pressure high; more 'push' on the piston. But a hotter piston top is also more likely to ignite the mixture before the spark does [ detonation ]. They don't tell you that when you buy the pistons....

My advice is to try & keep the incoming air to the engine as cool as possible:
- cold air induction
- improve cooling system
- block off &/or reduce size of exh xover in the intake
- water injection
- all of the above
Click to expand...
Used to have an ld4b and the crossover was terrible for my engine. Now use a Victor 340 intake and so much better! I definitely plan for cold air to carb/intake. Also looking to add a 3 nipple fuel filter to recirculate the fuel to keep it cooler I suppose.
 
Pretty much almost most of its existence. Only recall early on in its 1st incarnation it had a bone stock 360 distributor with factory curve and all. Still kb107 pistons. Back then had the 280 mopar cam and 3.55's out back. Now has 3.91's. Any back in its old set up I don't remember it pinging much if any. But that was like 12 or 15 years ago. Fuel was different I think. That cam was a 110° lobe separation vs the 292 purple cam with a 108° lobe.
 
QuickDart360 said:
10's or 9's?
Click to expand...
Yeah like N96 or RN9Y

R means resistor, N is for the long reach threads (3/4") as opposed to a 440 that uses J (3/8" reach) The numeral is the heat range and Y is extended tip

I think YC would be extended tip copper, no idea what some of the newer stuff is, or the "mini" plugs

I used to run 9's in my 10.5 (advertised) 71 340
 
take mechanical timing out of your distributor, whats your current compression ratio? with that camshaft i bet your motor would like alot more initial timing and less mechanical.
 
Maybe. It did with mine a little. What thermostat do you run? The number one biggest thing you can do to combat detonation is cool the engine temp down and cool down the incoming air/fuel charge. Of course cooling the engine temp down does the other. I had a 180 stock style thermostat in mine when I put the modified engine in and had some light detonation issues. I tried several things, including colder plugs and each made a small difference but the one thing that finally knocked it completely out was a 160 high flow thermostat. I have the factory temp gauge and before the swap, it would normally run a tic below half way to a tic over half way depending on outside temp. Once I put the 160 high flow in it, it just does make it to the first mark, no matter the temperature, and no more detonation, regardless of how hard I lug the engine. I highly recommend the thermostat. But it doesn't just need to be 160, it needs to be high flow as well. The trick is getting the coolant OUT of the engine as quickly as possible.

Hot 225 slant 6 with 175 PSI cranking pressure and 250 @.050 solid cam.
 
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