The J9's are a colder heat range plug than the J12's. Colder plugs are recommended when the engine is operated at high RPM's (3000-5000) as they are less susceptible to detonation. But if you plan to operate your engine at low RPM's (1000-3000) the colder J9's will most likely foul more easily. For low RPM operation, J12's or J14's are recommended to prevent fouling.
Now the last time I attempted to purchase Champion spark plugs, the only one's available were J-10Y or J-14Y so you may not have much of a choice of heat range as in the old days. Autolite 85's and 86's are equivalent to Champion J10's and J14's.
My "two cents" for what it's worth. I hope this helps.
Chris the K MANIAC
-----Original Message-----
From: Jim Maiani <jmaiani@xxxxxxxxxxx>
To: Chrysler300 <Chrysler300@xxxxxxxxxxxxxxx>
Sent: Fri, Apr 18, 2014 8:46 am
Subject: [Chrysler300] Spark Plug Question
Hi Everybody. I hope most of you are not looking at snow
yet. Unfortunately, here in northern Michigan, we are...
My survivor 1962 H needs new plugs. (127,000
miles) I’ve read where the recommended plug is Champion J-9Y; and the
1-4bbl 413 wanted J-12Y. The current plug (no idea how old) are Autolite
85. The local Advanced Auto Parts says I need Champion J-12Y. My
friends say just get the J-9Ys. If there’s anybody in the world that would
know for sure, it’s you guys. Comments and opinions please.
Thanks in advance for your help.
Subject: [Chrysler300] FW: 1961 Chrysler Newport
Wagon
-----Original Message-----
From: Anthony Ballato
[mailto:anthony.ballato@xxxxxxxxxxx]
Sent: Thursday, April 17, 2014 5:01
PM
To: CHRYSLER 300 CLUB
Subject: Fw: 1961 Chrysler Newport
Wagon
Check out my 61 Newport wagon for sale here and let me know if you
have
any
interest.
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