SPARK PLUGS - WHAT KIND DO YOU USE ?

[MATT47025]

Hey Guys,

 

I have a '51 Express with 6 volt system still in operation. What spark plug should I use? I bought a set of Champion RJ12 

but I dont know if this is what I should be using. 

 

[Don Coatney]

Suggest you do a forum search. This has been discussed many times with many different opinions. Bottom line is the choice is yours.

[Jeff Balazs]

Autolite 306 is a good plug in these engines.

Jeff

[JBNeal]

Flathead Tech 

[HanksB3B]

Autolite 306 is a good plug in these engines.

Jeff

 

+1 (what I've used for years)

 

Hank 

[jeffsunzeri]

You can use this site as a good conversion table:  http://www.sparkplug-crossreference.com/

 

RJ12's will work. You don't need a resistor plug, so anything from a J8 to a J12 will do as well. Check the plug color after running a few miles to see if the heat range is good in your motor.

[NiftyFifty]

Autolite are the best choice for any vehicle IMO, but the NGK plugs also work very well, I just replaced mine because they got a little rusty back when the headgasket blew a few years ago. I wouldn't put a Champion spark plug in my worst enemies vehicle

[Jeff Balazs]

Autolite are the best choice for any vehicle IMO, but the NGK plugs also work very well, I just replaced mine because they got a little rusty back when the headgasket blew a few years ago. I wouldn't put a Champion spark plug in my worst enemies vehicle

I would But I know what you mean.

[Merle Coggins]

Autolite 306 is a good plug in these engines.

Jeff

 

What he said... That's what I run.

[MATT47025]

Thanks for all the input. I always wondered why Champions plugs are so disliked. They been around forever it seems but no one likes them. 

[NiftyFifty]

Working in a shop where guys came in with "fresh tune-ups" only to have a miss within 5000k and almost every time they used Champion, it was a bad plug....gives you a bad taste. About the only thing they work well in IMO is single cylinder outdoor equipment, with the exception of sleds or dirt bikes etc

[48Dodger]

Resistor plugs are for ECU/PCU cars and trucks.....they keep the "noise" down in the ignition so the computer doesn't misread a condition of the engine.

 

Cold plugs: racing, towing, long hauls with a heavy load. 

Hot plugs:   daily driving, short trips, older engine.

 

Kind of gives you an idea of what you're looking at. Hot vs Cold plugs have nothing to do with spark energy, but rather its design to disapate heat. 

Think of a boxer in a cold enviroment (engine) or a hot enviorment (engine).......he's gonna throw the same powerful punch, except in one senario, he's wearing a long sleeve sweatshirt (Hot plug). 

 

48D

[Don Coatney]

Hot cold plugs explained.

 

[jeffsunzeri]

Seems like there are a number of "Champion Haters" and "NGK Haters" and so forth. All of them cite lots of experience with plugs going bad too soon, misfiring out of the box, or there being duds right out of the box.

 

The truth is that spark plugs fail for any number of reasons, the most common is mishandling, and right after that is mis-application.

 

You can never tell who has dropped or slammed a box of plugs in the trip from the manufacturer to your car's fender, and dropping a plug frequently leads to interior failures that you will never be able to see and may not be apparent immediately.

 

There is some overlap in heat ranges across manufacturers, so being at peace with a particular spark plug can sometimes take a little experience with a particular motor.

 

Champions are fine spark plugs. So are NGK. So are Autolite. So are Bosch. So are Delco. So are...

Edited April 23, 2015 by jeffsunzeri

[Don Coatney]

The truth is that spark plugs fail for any number of reasons, the most common is mishandling, and right after that is a mis-application.

 

You can never tell who has dropped or slammed a box of plugs in the trip from the manufacturer to your cars fender, and dropping a plug most leads to interior failures that you will never be able to see and may not be apparent immediately.

 

.

You may be very well correct on the mishandling. It has been my experience that Champion plugs must be delivered to the distribution centers via air drops sans parachute as I have had more failures with there plugs "out of the box" than I have had failures with any other automotive spark plug manufacture. To the credit of Champion plugs they do work well in air cooled lawn mower engines. But in automobile applications they are my last choice. 

 

As far as the miss-application that is the responsibility of the installer not the manufacture.

[Jeff Balazs]

My experience with Champions is they seem to foul much easier than the equivalent NGK or AC plug.. I've heard a lot of explanations for this.....and the one I have heard most often and makes the most sense to me is that Champions don't actually run within the specific heat range they say they do. I have seen a fair amount of evidence in the form of severely fouled plugs to support this. In two strokes and high mileage four strokes.

 

Jeff

[BobK]

 Started driving about 1965. First car a Ford Model A, then a '56 Chevy, and then only Mopar since 1968. Don't think I've bought any plug but Champion, and can't remember ever having a bad one.

 

 The discussion on plugs is on par with........

             Who is second best.... Ford or Chevy ( we know Mopar is #1)

              How to weld cast iron

              Holly or Carter carb..... etc.

[Dave72dt]

There was a period during the late 70', early 80's where Champion plugs  were running a about 50 % failure right out of the box and left a bad rep for a lot of mechanics, myself included.  That's a failure rate I witnessed first hand.  Company buyout, manufacturing facility change , material changes, quality control change, whatever,  something changed and the failure rate became unacceptable.  I assume they've made changes and the plugs are fine once again.  Sure, I've had other brands fail, but none like the Champions did during that period.

[cavisco1]

Use whatever brand makes you feel good. I've used lots of Champions in many MOPARS over the years without any issues. Currently running DENSOs, NGKs and Bosch Supers in our various daily drivers without problems. When I need plugs I usually just get whatever brand is on sale. I did have an Autolite plug blow out of the #6 hole on a Ford 300ci six, but I think it was more related to the poorly drilled and tapped hole from Ford than the brand of plug. Still running it with a thread insert, but lately the piston slap noise keeps whispering to me to trade soon.

 

Scott

[TrampSteer]

What he said... That's what I run.

What they said ...

[Bill Bartlett]

What about plugs like E3, or the fancy titanium plugs. Has anyone had experience with them?

[Jeff Balazs]

I have used Iriduim plugs made by NGK in an antique motorcycle I have. They work really well in old Ignition systems that have less juice going to the plug than modern systems. They will produce a real good spark with less pushing them.....in my application a 65 year old chain driven Lucas magneto. NGK's tech center used to be around the corner from my shop.....wish they had not moved.....they were very knowledgeable and helpful problem solvers.

 

Jeff

[Bill Bartlett]

Thanks, Jeff. Right now, my application is a stock '49 218 with stock ignition. The car runs pretty good. I have the parts to convert to a slant-six distributor. After I change it to 12-volts, I plan to put in a Pertronix electronic ignition. So the application will change as time goes on.

Do you happen to remember the number of the spark plug you used?

Thanks.

Bill

[Bill Bartlett]

I'm a dummy. I just re-read your post and rediscovered you didn't use them in a car.

What kind of motorcycle was it? Dad had a '47 Indian Chief. That was a cool bike.

[Jeff Balazs]

Bill;

I think you will find that due to the engine design we are dealing with all you are going to need is a plug like the Autolite 306. I have the 6 V Pertronix set up with a matched coil in mine. They suggest that you run a slightly larger gap... .040" but other than that nothing else is needed. I played around with some NGK's but settled back on the 306 as optimum. Gives a very easy start on the 6 volt system.

 

The bike I use an Iriduim plug in is a 49 AJS (Matchless) 500 single that has been built to 6 day trials spec. In the period from the late 40's until the early 60's these bikes by AJS were a dominate force in these events. In those days motorcycle sales were focused on the results in these 6 day events. All the european manufacturers placed great importance on these results.  Most of the AJS and Matchless winners were powered by the 350 version of this engine which had a square stroke. These engines could be lugged down to under 200 rpm and still produce usable power and good throttle response. This characteristic is especially useful in the technical off road sections considering the weight of these bikes and the limited suspension systems available at that time. The 500 I have is a long stroke engine which produces more power but is harder to keep running at these low engine speeds. It took a lot of experimenting to get the results I was after. In the end the swap to an Iriduim plug made all the difference.

I know most Americans have little or no idea about the ISDT or the other great six day events but to me they will always be the greatest and most valididated motoring events ever run. To this day the best score ever set in the Scottish Six Days Trials was one point off for 6 days and over 1200 miles of judged riding done by Gordon Jackson in 1962 on a 350 AJS.

 

Jeff