plug help for 440

[fastback340]

what spark plug would you recomend for my 440 (see sign.) I tried a set of ACs but they car hasnt run right since and i threw away the old plugs (autolites) so I'm not sure which to get. I'm use to using stock heat range plugs but this motor doesn't seem to care for them.

[JoeGrapes]

Your 440 is much like mine. I tried Accel 137, Bosch Platinum, Autolite Racing AR74 and Champion. The one's I like the best are plain old Autolite 75's Try 'em and see if you like.

[dirty dan]

Are you sure about the (75) auto lite? the book says 85 for a big block .
I have also found the auto lite to be best. Ilike to use 86`s in my stuff. Once upon a time champion was the way to go.
I don`t know what happened.
Either champion went to the dogs,or Autolite has come a long way. AC`s are for chebys and motor cramp is for ferds.
happy trails

[JoeGrapes]

Hi Dan, Autolite 75's are the one's I'm using. I get a nice light tan color on the tip. Your right about the Champion's, back in '72 on my '70 Roadrunner the Autolites were the only one's that lasted. Have a good one

[Belvedere65]

Autolites

[jlcoffell]

I myself have a 440 and have had on going plug problems.

From what I understand the Autolite 75's are the same heat range as the Autolite 85's. The 8 series are simply the resister
version of the 7's. This is what I have been told so accuracy ?

To go to a colder plug you want to drop to either a 74 (non-resistor) or 84 (resistor).

Problem is is that most places don't carry them.

I did some research and found through old manuals in the local library that 1969 440's used 2 different types of spark plugs.
The standard 440 used a champion rjy12c or something like that and the high performance model used the Champion rjy10c.

At the local NAPA store we crossed the heat range of an Autolite
85 as being the same as a Chanpion rjy11c.
If you go to a discount auto parts store they will give you the same plug for both the high performance engine versus the
standard. Makes since since they don't have to stock 2 different
plugs.

I run the Autolite 85's but they seem to only last a couple of weeks before I start getting miss-fires. Change plugs and eveything is good again for a couple more weeks.

Just figured I would pass along some of the info I have learned but will also follow this posting to see what some of the experts
have to say as I am curious as well.

[ehostler]

The Autolite website confirms that the 85 is a resistor plug and the 75 is a non-resistor plug and that both are correct for a 440. If you like Platinum plugs the AP 85 is the correct one.

[dirty dan]

Jlcoffell
When you pull them out what do they look like?
By the way thanks for the info.

[jlcoffell]

Well the plugs don't look good. When removed you can tell they are to hot of a plug. They almost have a silver like color to them.
Thats when I went to the library. Mopar in 1969 calls out like a champion rjy12c (or something like that, its been a while) for the standard 440 with like 9.5 to 1 comp. The HP version called out the rjy10c (again ?) with the HP having like 10.25 to 1. The discount auto parts stores call out the same plug for both the standard and HP models. I would bet that the autolite 75/85 is comparable to a rjy11c. 1 part that can be used for both minimizes inventory.
I am thinking that if I could find some champion rjy9c plugs they
would probably be very close.