Spark plug preference...Curious
 

IS there a preferred "Brand" spark plug for your flathead? What prompts the question is my best friend is a "Willys" guy and all the guy's on his support page prefer the Champion J8 for the Willys Jeeps!! They say they run best with them.....SO before I go buy a new set.... is there a particular brand like "Champion that is preferred say over Autolite??? Flathead in question is a 1939 Merc.

Re: Spark plug preference...Curious
 

NGK or Autolite for me.....some folks are not happy with Champion quality.

Re: Spark plug preference...Curious
 

I use only NGKs

Re: Spark plug preference...Curious
 

Fifty + years ago, the only thing I ran in several "go-fast" Chevies was Champs. As time went-on, the Champs became more and more prone to fouling. Later in the early '80s and to this day, I had some STOCK, factory hi-horsepower Corvettes that were all impossible to keep Champs running clean in. Changed to Factory-type AC plugs and the little Chevies love 'em. I've had the same bad results with Champs in my flatheads. Only Autolites for me any more. I know that "Kiwi" is gonna hate me for chastising his Champions. Just my experience! DD

Re: Spark plug preference...Curious
 

I use Autolite #216 in a stock motor. I’ve had the electrode pull right out of the porcelain when I pulled the wire off on two plugs. As of now,I haven’t changed to another brand.....Mark

Re: Spark plug preference...Curious
 

Would that be the NKG 7131???

Re: Spark plug preference...Curious
 

I use a NGK B6L when I need a 7/16 reach plug. They work well on both street and high-performance flatheads. Part number is 3212.

Re: Spark plug preference...Curious
 

It's Dead stock 39 Flathead.

Re: Spark plug preference...Curious
 

I use NGK # GR4 2635 plug with 11/16 reach on MCF heads vintage 1999.
That was the plug suggested by Mark Kirby of MCF.

Re: Spark plug preference...Curious
 

I also went to NGK for 2 reasons....first they have never so far failed in mysterious ways for no reason...and i can buy them in bulkpack for a reasonable price.

Re: Spark plug preference...Curious
 

1940, are you 12 volt Or 6 positive earth ?

Re: Spark plug preference...Curious
 

For the 3rd time, STOCK. 6V system, positive ground. Original 39 Mercury engine....NO aluminum heads, NO high performance JUST STOCK. AND numbers sure help a fellow, I've got 3 different NKG numbers, 3212's seem to be the one (Thanks Bored&Stroked).....but NKG's web page only has to 1950 SO not sure if an 8BA plug is good for 39 Merc???? The "plug" cross reference page I looked at listed "several" NKG numbers 3212 being one and 3112 being one, not seeing where 7131 is listed for a flathead BUT That is what NAPA's web page shows for a 39 Mercury????

Re: Spark plug preference...Curious
 

Re: Spark plug preference...Curious
 

I use the Autolite 216's.

Re: Spark plug preference...Curious
 

Any pros or cons using a resistor type. I know the newer cars w all the electronics & computers need them but also I’ve used them thinking it prevented radio / stereo interference?

Re: Spark plug preference...Curious
 

Me too !

Re: Spark plug preference...Curious
 

I use NGKs 3212 in my more or less stock avatar 40 engine. I like them because you can clean and regap them multiple times before they get tossed. I have never used Champions but had been using Aurolute 216s - more of a personal preference using the NGKs .....

Re: Spark plug preference...Curious
 

NOS 3 piece Champion C7's in my 1934.
20000 miles on the current plugs and still going strong I have a spare (and a half) set if I ever need them. When I got the car it was running Champion D21's . Nothing wrong with them just not original. The D21's are still doing sterling service in my 1910 Hupmobile-Bearing in mind that the fire is lit in this by a an early HT Bosch magneto -If the plugs aren't tip top you would know pretty quickly

Re: Spark plug preference...Curious
 

The best choice of plug for your Flathead as others have mentioned is the NGK B4L or B6L the NGK plug works perfectly for stock as well as modified applications being 6 or 12 volt neg or positive ground has no effect over the spark plugs performance. The Autolite 216 is a second choice but is in no way as good as the NGK . Champion plugs being made in mexico are prone to failure so what ever you do stay away from that brand. Ask your NAPA salesman for the B6L plug no need to try and figure out the part number.
Ronnieroadster.

Re: Spark plug preference...Curious
 

Never use a resister type plug with a 6 volt system their design is for much more modern ignition systems the original flathead systems do not fall into that category. In other words not enough coil potential to get a good spark with 6 volts
Ronnieroadster