Read my Spark Plug

Messages
2,205
Location
california
NGK GR4GP
~25K miles
Rebuilt Mopar LA-318 / 5.2 liter V8 w?~ 60k miles on rebuild
Plugs removed after completing 2500 mile journey in 4 days.
Some Gumout regane still in tank at beginning of journey

https://www.ngk.com/ngk-2763-gr4gp-g-power-platinum-spark-plug
20210116_162110.jpg

20210116_162127.jpg

20210116_162141.jpg
 
Messages
1,759
Looks like the engine is healthy, no signs of burning oil. But it does appear there is some deposit up, usually from excessive fuel additives.

It also looks like the engine runs a bit rich. Could be an engine tune issue or could be certain fuel additives being used that inhibit proper combustion. Not bad for 25k miles.
 

wrcsixeight

Thread starter
Messages
2,205
Location
california
Thanks. Engine burns very little oil. Its about 1/8" below where I started at 2500 miles ago and some of that loss is the freaking valve covers whose bolts love to loosen up.

The Gumout Regane was added about 2700 miles ago and perhaps every ~11K miles before that on these plugs.
The last tank of gas of the 2500 mile roadtrip was Chevron, then Shell, then Valero twice, then Pilot. About 425 miles between fillups, can go farther on a tank but prefer to not draw it lower. Not sure if Pilot qualifies as top tier fuel, but Shell and Valero and Chevron do.

Pretty much getting the expected mileage, but always hope and try for more.

Wondering about opinions regarding heat range. When not doing long cross country drives most driving has been extremely short trip as of late, generally to store and back 1.5 miles away..

Engine calls for Champion Plug Type RN12YC.

Seems to run the same no matter what plug I have used in the past.

Someone suggested a slightly colder plug with an extended reach on this engine for better driveability and MPG's.

This plug is a 4 the 'someone' recommended plug is a 5 on NGKs heat scale.


HEAT-RATING-AND-HEAT-FLOW-367x362.jpg
 
Messages
6,878
Location
Roanoke Virginia
Doesn’t look too bad. As far as the hotter or colder spark plugs I’m not sure but one of the Mopar guys on here I’m sure could tell you more about them and if they are recommended for your vehicle or not.
 

wrcsixeight

Thread starter
Messages
2,205
Location
california
It's a rebuilt 32 year old engine with throttle body fuel injection.

My old man (83yo) thought it looked a bit lean.
That is plug number one. Number 8, furthest from water pump, is not as happy looking but my pics of it are not as good.

20210116_163154.jpg 20210116_163207.jpg 20210116_163212.jpg

Champion's 12 heatrange corresponds to NGK's 5 and a 4, in the photos above, is a hotter plug.
 
Messages
2,304
Location
Seattle-ish, WA
My instinct is also to say a little lean, BUT:

2,500 miles in four days.
Regane (I'm a big fan of it myself, use it regularly on all cars) in before the run.

I'd say fine all given, take a peak after more normal use. This isn't a fair sampling.
 
Messages
5,162
Location
Ohio
2500 miles in not much. Does look somewhat lean. If you look at the ground electrode, you want the color change about in the middle of the bend. Yours indicate too much timing. You also want about 2-3 threads "discolored" which indicates a good heat range. Yours are hard to tell from only being in use for 2500 miles. They do seem to be "slightly" towards the hot side. Long ago when I had the 318, I always found that engine ran best for me with the Champion RN12YC plugs. The engine was quite finnicky with the plugs used.
 
Last edited:
Messages
15,868
Location
N.H, U.S.A.
I would prefer non extended tip plugs in that engine. What is the Coil setup any CD boxes or MSD.
You can loose some spark peak firing voltage and change timing with the "easy to spark" Ir or platinum fine tip plugs
which would require a tuneup adjustment.

Looks like a lot of previous buildup was toasted off - like taking Grannies car out for a HIghway blast.
 
Messages
7,981
Location
MI
You can loose some spark peak firing voltage and change timing with the "easy to spark" Ir or platinum fine tip plugs
which would require a tuneup adjustment.
I never heard this. Can this concept be explained? Would this apply to a modern computer controlled engine?
 

wrcsixeight

Thread starter
Messages
2,205
Location
california
The plugs have ~25k miles.on them.
~2700 miles since the gumout Regane was added to fuel tank.

Engine is throttle body fuel injection in a state with smog inspections meaning little tuning i can actually do.

Ignition coil is new. Just a standard motor products uc-16

Ignition timing is set to 16btdc.
Has to be set to 10 btdc for CA smog tests but throttle response feels way better at 16 soi bump it up after passing.

Most of 2020 in between the cross.country jaunts... it only sees short trip driving. Perhaps 500 miles worth.
 
Messages
1,096
Location
Arizona
The emissions system is designed to run/cruise lean so it looks OK for that. A little more tan on the insulator would say it had good get up and go fuel mixture. A good tuner could make it run better and still pass emissions. I would not mess with different temp plugs, Hotter could overheat especially running lean. and colder could abruptly foul out if oil starts burning in one of the holes.
 
Messages
15,868
Location
N.H, U.S.A.
The plugs have ~25k miles.on them.
~2700 miles since the gumout Regane was added to fuel tank.

Engine is throttle body fuel injection in a state with smog inspections meaning little tuning i can actually do.

Ignition coil is new. Just a standard motor products uc-16

Ignition timing is set to 16btdc.
Has to be set to 10 btdc for CA smog tests but throttle response feels way better at 16 soi bump it up after passing.

Most of 2020 in between the cross.country jaunts... it only sees short trip driving. Perhaps 500 miles worth.
That is a BIG timing bump. I never change base timing more than 3 degrees in either direction and typically 2 at most. I would guess your vacuum advance control or mechanical advance is not working properly. I have done hundreds of tune-ups professionally in the 70s and 80's

Some of that junk on you plug may be due to ping
 
Messages
15,868
Location
N.H, U.S.A.
I never heard this. Can this concept be explained? Would this apply to a modern computer controlled engine?
Yes, its basic ignition physics. But most modern engine have "miniature" coil on sparkplugs with finewire Ir centre electrodes.

I would do my own research into this, instead of getting "misinformation" off a non-professional forum.

here is a link to start:

 

wrcsixeight

Thread starter
Messages
2,205
Location
california
That is a BIG timing bump. I never change base timing more than 3 degrees in either direction and typically 2 at most. I would guess your vacuum advance control or mechanical advance is not working properly. I have done hundreds of tune-ups professionally in the 70s and 80's

Some of that junk on you plug may be due to ping
Tbi. No vacuum advance. Have to unplug coolant temp sensor to set base timing.
Does not ping until about 19 btdc with 87 octane at near sea level.

California allows.+/-3 degrees to pass smog, and they do actually test obd1 vehicles.
My next test is in July.
 
Top