440-1 spark plugs

[alterego_k]

Hello DaveBA78Chieftain. Do you have the spark plug specs for a 440-1 which is non-tapered?  Going in a '78 (dodge m400) Executive, The Diplomat II with dodge 440-1 (verified on block; head seat is visually verified as non-tapered) Thanks.

[DaveVA78Chieftain]

Altergo_k,
I am answering here rather than private e-mail for the benifit of others.   Your M400 chassis originally came with a 440-3 so someone along the way either replaced the engine with a 440-1 or just the heads with 440-1 heads.  Given we do not know what a PO did, the first step is to determine which head casting number you have.  Unfortunantly that does require removing the valve cover.  Once you have the head casting number, you can then cross that over to year the head was actually used: http://www.mymopar.com/headcastnumb.htm



Lets say it was 3769975 (1975 400/440).  You also know that only cars used the 440-1.   Because of the emissions changes, about the only car that had a 440 in it in the mid to late 70's is a Chrysler Imperial.  So, looking on NAPA you find AC Delco R43S as the base plug for a 1975 Chrysler Imperial with a 440.  Cross ref to other brands: http://www.sparkplug-crossreference.com/convert/AC_DELCO/R43S

Specs for R-43S:
Flat shoulder with gasket
14MM threads
9.5mm reach
Gap 0.40"


R43S crosses to Champion number RJ12YC however Champion site says RJ14YC for a 75 Chrysler Imperial which is a hotter plug.  I would start with a cooler plug (i.e. RJ12YC) to help avoid pre-ignition and plug tip overheating.  If that exhibits premature fouling then move up the hotter plug (i.e RJ14YC).

Just remember this a workhorse application not a racing application.  You want cooler plugs to pull the heat away from the chamber which is why Dodge designed the 440-3 heads with "extra" cooling passages around the plugs.  Hotter plugs can also induce pinging with today's gasoline mixtures.

Dave

[Elandan2]

Our motorhome has a 440-1 engine.  I re-built it in 1985 with a 440 from a 1973 Chrysler Newport Custom.  I have had the best luck with NGK V-Power, XR5 plugs.  Just a standard plug, with the V-groove.  Rick