spark plug recommendation

[Brads70]

I'm fed up with NGK I think? Or I have the wrong plugs for my application ?
I've been using NGK R5671A-7 stock # 4091 plugs for a few years. Problem is they seem to just quit for no good reason?  Today was the first warm sunny day since last year, I've been firing it up letting it warm up once every other month or so, ran fine. Today fired it up and was going to go out for a nice cruise, it was hard to start which is not normal at all. Ran like crap then realized it was missing on a cylinder.    I have been having to replace these plugs every year and I don't put a lot of miles on it like maybe 3000 miles a season? I'm no spark plug genius but sheesh they should last longer than that!
What do you all recommend? I'm ready to try something else. I have a new set or NGK 4091's sitting here ready to use but....
Another local guy uses autolite AR3924 ? I use Champion RC12YC in customers lawn tractors? I have heard of people using them in cars too?
Any thoughts , opinions?

Engine specs
451 stroker
Stage 6 aluminum heads
lunati hyd roller   http://www.lunatipower.com/CamSpecCard.aspx?partNumber=60312
headers
850 DP quickfuel
always use 91 octane ethenol free gas ( shell premium )

@Chryco Psycho

[Chryco Psycho]

That has always been my experience with NGK , Glad I am not the only one !! Maybe NGK is No Good Krap
I have used RC12YC as well  , beeter plug IMO
Autolite is a good plug also

[RUNCHARGER]

I've had good luck with Autolite, even AC Delco.

[fc7cuda]

Autolite here too. 

[BIGSHCLUNK]

Ya.... Autolite in my HEMI too

[JonH]

Just a thought, but are you sure you have the right heat range plugs? You obviously have a non stock application and if your plugs are too cold it will run poorly. How did you arrive at your current choice (heat range)? I have used NGK in many engines over the years, and never had a problem. (have used most of the other brands as well without issue)

[Chryco Psycho]

The heat range seems to fine while driving , it is the cold winter starts where the plugs don't get a chance to fully clan off the soot , other makes seems to resist fouling far better .
My experience over a lot of years is that NGK will foul & quit firing far faster than most plugs , you cannot clean then & get them working again either , I have always had better results with Champ or Autolite Plugs

[ledphoot]

Autolite Double Platinum works for me. Champions are OK until you go to remove them, they get brittle with heat.

[Brads70]

Just a thought, but are you sure you have the right heat range plugs? You obviously have a non stock application and if your plugs are too cold it will run poorly. How did you arrive at your current choice (heat range)? I have used NGK in many engines over the years, and never had a problem. (have used most of the other brands as well without issue)

I suspect they are not the correct heat range?  When on long runs they are fine. I've pulled a few plugs ( Neil has also) after a 8 hour drive to Carlisle are they are great. ( tan coloured) it seems to be idling and short trips around town where they foul up. I do try to start it up once a month during winter( when/if temps get above freezing), let it warm up to operating temps.  I do have an Air/Fuel gauge and watch it constantly. Carb is tuned fine, runs great otherwise. Car is great on fuel for what it is. Seems plugs don't like idle/low rpm ?

[THE ZUKE]

   I want to follow the discussion 

[JonH]

Not an expert here but plug color is not an indication of heat range. It is an indication of fuel mixture. I have had plugs that were too cold and the idle was horrible. Google heat range and how to check if you have the correct plug. If it was me, I would go 1 step hotter and see what happens. Might even need to go further than that. Keep us informed as I am sure others with modified engines would be interested in knowing how you solved your issue...

[Chryco Psycho]

I agree to a point , but a too cold plug will not burn off the over rich contamination  properly

[JonH]

I agree to a point , but a too clod plug will not burn off the over rich contamination  properly

True statement, but he is indicating he has a well tuned carb. Issue appears when idling and start up. Classic heat range symptom on an otherwise well tuned engine. Starting the engine and idling until warm will not burn deposits from the plug as well as sustained driving under load. Hence I think a hotter plug is called for. In looking at the ngk plug chart, he is using the absolute coldest plug made for his application. I think he would see a tremendous difference by going about 2 steps hotter. Also never have been convinced that racing plugs are a good idea in a street car....

[HP_Cuda]

I've used Champion RC12YC plugs and they work well. My rich condition is my fault and I have AFR just haven't installed it yet. One other reason I use them as they are recommended for my heads as I need the longer SP.

I'd recommend taking a look at this chart so you can get a better understanding of heat ranges across the different brands:

https://www.briskusa.com/spark_plug_cross_reference_heat_range_chart

[Brads70]

I've used Champion RC12YC plugs and they work well. My rich condition is my fault and I have AFR just haven't installed it yet. One other reason I use them as they are recommended for my heads as I need the longer SP.

I'd recommend taking a look at this chart so you can get a better understanding of heat ranges across the different brands:

https://www.briskusa.com/spark_plug_cross_reference_heat_range_chart

I will try those next as I keep them in stock for Brigg's lawn tractor engines. They have a extended tip so I'll have to install one and roll it over by hand to make sure nothing hits.
Sounds like I'm not driving it hard enough! 
" But officer, the guy on E-Bodies.org said....."