John,
In addition to my 300G, I also
have a 2006 300C Heritage, with the 5.7 Hemi. Factory
recommends 30K spark plug replacement, which I did. Plugs
did not look worn, so I did a bit of research and asked around, it seems there
is a concern that if the plugs are not changed at recommended intervals, the
plugs can become difficult to remove and the threads bond to the
head. Due to this concern, I always use anti-seize on spark
plug threads before installing.
From: John Grady [mailto:jkg@xxxxxxxxxxxxxxxxx]
Sent: Monday, December 28, 2015 12:32 PM
To: 'Bob
Jasinski'; 'list server'
Subject: RE: [Chrysler300] G spark plug
recommendations
I saw a long
test somewhere on plugs, a real objective test ---and yes , Bob, Autolite won
it , for “normal” conventional plugs, also NGK was right there . Champion came
out at bottom. Why? Who knows, just the way it came out. They reduced volts,
ran hard , dyno HP , etc etc Cannot remember details perfectly
now. But if you went above the “normal” $ plug, dual ground electrode Bosch
(platinum) came in as best plug. Interesting that more expensive Bosch ones
with 4 grounds did not. Discussion was there, saying 4 grounds ?? shields
initial lightoff, so ?? HP drops slightly . Bosch English descriptions
confusing, one with 2 ground electrodes called 4 gap or something.
Watch out. Got wrong ones first.
Why I was SO
into that plug info , about 5 years back, I had an interesting experience, for
what it is worth, on 97 JEEP 4.0 from new ; had factory HD long service
special plugs , platinum I believe , supposed to change at ~ 30K(??) , I did
not, they were firing fine . My own .02,= if they light the gas, no
skip, they are working fine. Rest of it (the widely dispersed BS) gets filed
alongside 2000 mile oil changes . I eventually drove that JEEP to 305k. And
similar 02 4.0. I think 4.0 right up there with slant six. Maybe
even better. Interesting fact, 4.0 AMC had more HP and torque than MOPAR
truck 360 v8 in 80’s..
Although
Chrysler managed to screw up AMG design with dirt cheap, thin wall
pistons that crack the skirts at oil ring at 150k. About 2000 MY
up.
But one day,
JEEP with hi miles on plugs started to skip / run rough occasionally at 60-70
mph at about 105k after engine change . (ex ran it out of oil—that took 35 k
miles) . So thought ,hmm NOW I do have to change the plugs. One day soon,-- as
soon as rush is over. ! Within 1500 miles it basically suddenly stopped
running, after limping for 5 miles, died at side of road. My “mental
diagnosis” went immediately to coil (had died before --coils crack on 4.0 ,
before coil pack design, as rust on exposed E-I type coil core mounted
near front of motor causes mechanical swelling, cracking the coil epoxy(
bring back oil filled coils!) ) ; so changed coil again . No go..went
though ignition etc all that stuff. Finally got into plugs, new Bosch dual
ground plugs , it started right up, ran perfectly. So ALL the plugs
failed essentially at once at about same miles. Really wild thing that is!!!.
When pulled, ground electrode was almost gone, very wide gap, sharp
point left (sharp was/should be good!) . Lots of knowledge-- in my opinion--
in this. Gap opens, by itself , by burning ground, you should check it, reset
it, certainly ~ 30k or so. –gap too big, =no jump. . Dual grounds on
plugs are probably very good things , ought to help this 2X? . Platinum or
Rhodium sharp small center electrode that does not burn is a very good thing.
I bet if I had bent what was left inward it would have run another 50k .
Not advocating any of this, but really good info . After all, from engineering
view, a plug only has to carry electricity in , to the gap; if ceramic
insulator is clean and not shorted, (says engine is ok, rings etc—no
carbon ) what else goes wrong? Deposits? Maybe in 1960. Lead. But clean gas ,
clean running, and high power spark from electronic ignition, now the ground
side apparently burns off first, and it cannot jump the larger gap..or it
jumped somewhere else outside the plug due to higher volts needed outside to
jump inside gap (tower to LV 12v nuts not uncommon on MOPAR , almost
says loudly to you: burned ground electrode , or open wire ---if you see that
jump at night—resulting skip drove me crazy on B block 383 Charger and 440
challenger back in the day, when ~ new—mainly in rain by the way—one wet night
opened hood in dark and saw it jumping to nuts at coil tower !!) Silicone
grease fixes that, and cleaning tower.
Lately
revisited this plug story for slant six with a slight one cyl skip, about 25
-30 k since rebuild. Went to slant six guys site, they swear by certain NGK.
So spread the love. Put NGK in it. But for high performance and longevity,
would still go Bosch with two ground electrodes.
Aside from
above, all regular plugs of correct heat range will work. New. Differences
really should be non existent?
And Autolite
or NGK may be best of those, over the long term
New is
apparently less than 30k on them.
John,
I run Autolite 85 plugs in my G,
and it runs fantastic, even with fuel containing ethanol. Follow the
tune-up procedure in the factory service manual.
Happy
Holidays!
What is the latest recommendation on spark plug type/brand
for 61G?
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