340 Sparkplugs

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Duster72

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I recently had my 1972 Duster 340 engine rebuilt to factory specs,except a little hotter cam was installed..The manual calls for Champs N9Y plugs,however I would like to try NGK plugs..What NGK plug would work good for this application..The gas nowadays is crappy,so I wasn't sure if I should go with a hotter or colder plug..I was thinking of installing the NKG 2763-GR4GP G-power plugs..Really need some insight here..Thanks everyone..
 
Run the Champeons , I've never had a problem running with them I use the rn12y
 
Thanks for the quick reply..The RN12y..Is that a hotter or colder plug??..also would the gap still be .035..I have about 1300 miles on the engine,but seems to miss a bit at higher rpm's..N9y's are currently installed..just thought I'd try different plugs as lot of the guys seem to be using the NGK's..
 
If you are running the stock compression (8.5:1) the NGK GR4 V-Power (part # 2635) will work. A colder plug is the GR5 (2851), this will work well with 10:1 compression.
 
A step cooler or hotter plug will not make a big differance in a mild mill. Racers do this and find some ET or MPH I. Very small amounts. Stick with the stock heat range. 1 up or down is more than enough. Plug brand is often drivers choice. I stick with the Champs.
 
rumblefish360 said:
A step cooler or hotter plug will not make a big differance in a mild mill. Racers do this and find some ET or MPH I. Very small amounts. Stick with the stock heat range. 1 up or down is more than enough. Plug brand is often drivers choice. I stick with the Champs.
Click to expand...

True expect for pinging it can help/hurt. I wen from a projected plug to a non projected plug and kissed my pinging issues good bye, I'm using racing plugs...NGK R5671A-8, cheap at $3.49 a plug--was $2.49 last year
 
Isn't NGK made for Japanese cars? I remember working on Mitsubishi Eclipses etc. back in the 90's and those engines didn't like running on anything but NGK'S. Mopar ran Champions stock through the 60's and I am not sure if they still do. The modern engines are high tech and Champions were always regarded in the circles I used to hang with as lawnmower plugs. I always ran Autolite in my small block Mopar. I think Autolite 65 in my 340 and 63 in my 318.
 
Nevermind what the plug came in or what it was made for. The bottom line is how it acts in your engine and car. Considering the inexpensive price of plugs, this is something you can afford to do a trail and error test.

Personally, I can't stand Autolites in my MoPars.
I've run a lot of different manufacturers plugs and personaly like the Champs best. But that's me and my engine!

It is IMO that you start with the stock 340 plug and then try a step cooler. Then 2 steps cooler. See what the engine like the best. Dodge Freak makes a good note. HIS engine like one thing, MY engine like another.

At there cost, enjoy the experimenting. Go enjoy some track time for back to back testing (be aware that conditions change through out the day and will effect the slips more than the plugs will) or long distance traveling for mileage and drivers feel.
 
My plug is close to perfect, it will foul in cold temps if I let it run under 1,500 too long. The projected plug is the way to go IF you got enough octane for it. My engine was border line with straight pump fuel, most of the time it was OK but not all the time. So I tried non projected plugs without touching the timing and I have yet to hear it ping, HP did seem a tad off..I have yet to re ET it at a track

I run a MSD 7 box and HVC with those plugs, I';m sure the cold fouling issue would be worst without a hot spark

BTW if you have a miss now, new plugs likely won't cure it..the only time I had a miss at high speed was when one plug boot was crack and leaking the spark to a header pipe..so check those wires and boots if you do change the plugs..I'm running Champion wires I got off Ebay..Nascar Wires I looked under
 
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