fivepoint

I have set of rebuilt heads that I have questions about. The casting number on them is 4006452. My research says that these are 400/440 heads used from 1976-1978. The problem is they have the smaller spark plug hole. I thought that these would use a plug like a RJ12YC. Instead, a plug like a RC12 will fit from my 93 dakota 318. The parts stores I visit cannot find a 440/400 equipped vehicle that required the smaller plugs. They say all 400/440's in that time period call for RJ12 or RJ14. Has anyone run across this before? What are the correct plugs for these heads? Any help will be appreciated.

1966sportfury

the autolite part# is ap85..85 with a .35 gap.. that refrences with your rj12yc.. rc12 crosses with nothing that i can find... sounds like a champion plug..im sorry

fivepoint

Today I tried the AP85 plugs. They will not thread in. I have confirmed that it is a 14mm thread. The problem is the length of thread. Even when I try to screw in my compression tester, I have to use the adapter with the longer thread. Were there any 400/440 engines built in '76-'78 that used the longer threaded plug? If so, what plug number.

1966sportfury

not that im finding i went thru the autolite data base. and they are all the same plug.

2002ram440

i had the same problem, i have the same casting number on my heads. mine came out of a 78 motorhome. They are 81.5cc heads and they use a plug with the 5/8" socket. I finally just went to parts store and asked for a plug for a 78 corvette. These are the right fit but i was not sure of the heat range. I found a guy at my Advance auto parts store that used to have several mopars and he sold me the plugs that he said were the right ones. I am at work right now but I will look when I get home to give yout he number. They work just fine. Also, the corvette plugs worked fine too.

fivepoint

Hey thanks Ram440. When I saw motorhome , I did more digging into the books. The correct plug is a Champion RV9YC. Its a taper seat plug and fits the 440-3 engine. I wounder why Chrysler put those in motor home engines? By the way, I kind of miss Florida, I was stationed at MacDill for 6 years.

2002ram440

that number looks familiar, it may be what i have in mine now. I will confimr back.