At 11:57 AM 3/13/01 -0500, you wrote:
>Boy a little bit of knowledge sure is a big problem. I called around looking
>for Autolites 3923 and there was a store locater for Autolite plugs, not the
>least of which was Wal-mart but they didn't have that number. One of the
>suppliers said they didn't carry Autolites but could sub a Champion and
>came up with a number RC9YC4, and when I told him it was for a 98Dak 5.2L
>he mentioned RC12LC4 as was suggested by Chrysler. He said that the one
>I'm looking for was a whole different plug. Can someone inform me of the
>reason for this type of plug. Keep in mind I do not go to the track and the
>only time I see 5K RPM is when I look at the far right side of the speedometer
>but my needle never sees anything above 4K and that s rarely. This quest for
>perfection sure is confusing . Leonard A. Price
The Champion RC9YC4s, which are equivalent to the Autolite 3923s, are designed
with a bit thinner and shorter center. This design is what the
manufacturers came
up with as a best compromise in driveablility/wear/economy for cars. The books
will list these plugs for the 5.9L magnum or LA 360 engine but does not mean
that they will not be fit for the 5.2L magnum or LA 318 engines.
The Champion RC12LC4s, which are equivalent to the Autolite 5224s, are
truck plugs with their thicker and longer centers. This is what the
manufacturers
came up for pickup trucks as a best compromise for plenty of low end torque and
for drivlng mostly of in the 2500-3000 rpm range.
The 3923s are one range colder plugs while the 3924s are the normal heat range
plugs. Colder plugs are used if the engine is pinging a bit in hopes of
eliminating
the pinging because colder range plugs will dissipate heat away from the
combustion
chamber quicker. Colder plugs will also tend to foul up more/quicker with
normal street
driving.
Why you see the 3923s mentioned so much on the list is because they produced
a bit more rear wheel horsepower and torque (dynoed by DMLer Jon Smith) on the
5.2L and a number of DMLers were experiencing pinging in their engines. I
don't
know what Autolite does in their design/manufacturing process but they
contininued their reputation for putting out performance plugs which began
with the muscle cars of the 60s.
General experience on the list (mine included) is that the Autolites produce
a little smoother idle and wear longer than the Champions. They are also
not very expensive.
While different manufacturers list equivalent part numbers for plugs, this does
not mean that they perform equally for a particular engine.
First you need to decide if you want a truck plug or a car plug. Then you need
to decide which manufacturer, and, finally, what heat range. If my driving
needs
matched your driving needs (and assuming your engine does not ping), I would go
with the Autolite 5224s gapped at the recommended 0.040", having experienced
how my truck ran and how the plugs wore during the first year with the stock
Champions. Notice that this is a 'truck' plug with the normal heat range ...
the only difference being brand selection.
Personal 63 years opinion/experience: If you're searching for perfection,
you'll never
find it.
Hope this helps.
Bob
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