question for spark plug pros

[73chargercali]

when i tuned up my 440 2 years ago i just replaced the plugs with the same type autolite 85 now that i'm shooting for more power my edelbrock nitrous kit calls for champion RC-12-YC so i bought them and installed, checked for clearence and found no issues but the threaded shank is almost twice as long? is anyone using the same champions or had problems? i wanted to know how far into the combustion chamber the old and new plugs sit?

so are the autolite 85 the correct length of threads my guess would be about 3/8" or are the RC12YC the right length my guess about 3/4". will i run into problems? any help/info will be much appreciated.

[tan top]

  champions with 3/4" thread will reach too far into the combustion chamber .champion plugs the correct  length start with J,  example  original plug was  J 12 YC , witch is about 3/8"s reach. every type of plug made for mopars  R AND RB  engine  with factory OEM and cast iron heads  had a spark with 3/8"s reach,  unless i am mistaken hope this helps

[73chargercali]

so if i get j-12-yc it will be correct? does champion make this size?

thanks for the answer the car runs well enough but i'll try and pick up a set of the j plugs. thanks tan top.

[tan top]

just checked the manual , as the information i gave was from memory , champion  j 11 y plugs were factory equivlent , then i believe they discontinued them, i have run  champion j 12  y  &  j 13 y  and  currently run  ngk  plugs on the street   can't tell you the number yet, as my charger  is locked away in storage, but for running  NO2   , i think you might need a plug with a colder heat  range , but i  can't be 100% sure i forget.  try  phoning  some spark  plug  tech lines , accel and autolite   would probably do the plugs you need in different heat ranges,
or some of the guys on hear who run NO2 in their 440 might be able to help  with more info.
  the current champion plug for a 440 is RJ 12 YC , don't no what the R means though , may be radio suppression ,probably totally wrong on that though.

[greatwn73]

Just checking the current Champion catalogue

R= resistor
J= 14mm thread,3/8reach, 13/16 hex
12= heat range
Y= standard projected core nose
C= copper core

this is the correct plug for standard application 440 4bbl from 67-74,the 440 2bbl took a hotter plug RJ14YC

a colder plug will dissipate the heat from the tip of the plug better but is more prone to fouling-- the next heat range down from the 12 is a RJ8C

there is a Champion tech line 1-900-486-0040 (chargeable) and a free fax back line 1-888-819-5681 for any questions
ps for Canadians the tech line is still free.

best suggestion I could give would be to run the 12s and remove and check the the tip of the plug black=too cold,white too hotand brown just right

[73chargercali]

i picked up j-12-yc they arn't "rj" so no "resistor" for radio noise, i don't even have my antena(sp)  hooked up. the other plugs i bought before were already different colors, some black, some tan, a few had white on them after only one day of use (20 miles, if that). thanks for the help everyone.

[73chargercali]

so i drove the car today and over 1500rpm it runs like crap. i can hear little "booms" from the exhaust and it idles and accelerates like crap. my unexperienced guess is now my heat range is too cold on the plugs, i adjusted timing and it idled better but still had pops and booms from exhaust.( sounds like downcompression noises) i haven't looked at the plugs since they are a pain to get in/out. please help

[Nacho-RT74]

I would love to find Rs sprak plugs, but here is imposible, only J12YC.

ase Rs plugs still available up there ?

that what Haynes manual says to our cars ( RJ12YC )

[73chargercali]

yeh the "r" plugs are avalible but both stores i called said they would need to order them as they didn't stock them. so i just got the j12yc instead, was told the resistor is bad for performance.

[greatwn73]

73chargercali;  if you have multiple colored plugs its time to look at some of the basics

       1. did you gap the plugs before installation
       2. check your plug wires and if two plugs fire in sequence make sure the that the wires are seperated (crossfire will cause detonation)
       3. make sure you don't have a manifold leak a lean burn will whiten the plugs

all plugs should be the same color if carburation and ignition is correct.forget the heat range for now and find the cause.

nacho; I can get you some plugs and i'll check to see if there is a flight going down , if not i'll check the cost of postage. keep in mind the resistor plug has less voltage at the tip

[firefighter3931]

NGK XR5 is an excellent plug for iron headed big blocks. 

Ron

[TylerCharger69]

I'd start with checking distributor cap for cracks....then wires, then points, or rotor  whichever you have   points should be at .017...  gap i believe... and the electronic  is supposed to be .008 between the pick up coil and the shaft....if anyone feels those are the wrong  measurements...please tell me.  look for vacuum leaks...at the carb base, manifold base, and hoses.....sometimes those pesky headlamp door vacuum systems could have a leak....even at the switch itself.  If those  seem okay...maybe  try a higher heat range plug.   Otherwise....you may have mechanical problems.  By the way.....I'm assuming you have a stock ignition system??

[Nacho-RT74]

I don't know points but that's correct for elec pick up gap.

and .035 for spark plug gap

[TylerCharger69]

 

[73chargercali]

fixed problem two plugs had almost zero gap one was touching the electrode??? i guess i just wasn't paying enough attention when installing. but it runs fine and has the normal ehaust tone.

thanks for everyones info and help.

[TylerCharger69]

I'm glad that it was nothing serious.....Sometimes  when we install plugs,  we kinda close the gaps trying to install them by not getting the plug in the right place.  Also..food for thought.....a lot of parts houses say the plugs should already be pre-gapped,  but  getting shaken in the boxes,  or being dropped during shipment changes them...I always  gap them myself just to be sure.