CraiginMO Allis spark plug page
I am doing this web page to pass along information on Spark plugs. My Gleaner E combine with a 226ci D-17 motor and my '53 WD 201ci engine, both have points ignition and both have the same tall head that can use a 3/4" reach plug. Original plugs for theses engines were AC 45 which are no longer available. Most people say to use the Autolite 295 or 303 plugs. These plugs only have a 3/8" reach leaving a lot of threads in the head to collect carbon, not to mention the fact that the spark is actually hidden from the combustion chamber by about 1/2". I also been told that the older motors (with points) do better with NON-Resistor plugs and originally had copper plug wires. The 303 plug is a resistor type and as a matter of fact Autolite make very few non Resistor plugs. The closest I found to a good match in these tables is the 295 but again the 3/8" reach may be a problem. SOOOOO, I am researching a better alternative to the Autolite 303 plug. I will post pictures of the plugs after 50 hours in my WD motor. This will take a year or so to complete and my hope is to find a better suited plug for my WD and Gleaner engines. (note: if I had the electronic ignition conversion installed I would only use resistor plugs)
Current Status:
22 Aug 2007 - Champion plugs pulled an checked last week. see bottom of this page for results
10 April 2007 - Changed from Autolite 306 plugs to Champion N9YC
Autolite 306 results HERE (updated 20 April 2007)
Latest results HERE (updated 20 April 2007)
Good explanation of plug construction and heat range HERE
Good explanation of plug wires and NON-resistor plugs HERE
Current thinking on Autolite plugs:
Allis Chalmers WD45 (226ci) Autolite295---Non resistor---14mm----3/8" reach---standard electrode (hotter)
Allis Chalmers WD (201ci) Autolite303---Resistor---14mm----3/8" reach---standard electrode (3 steps colder)
Plugs to be tested. Others may be added as test results are obtained.
3/8" reach
Autolite 295, 303, 306
Champion J8C
3/4" reach
Autolite 403
Champion N9YC
AUTOLITE DATA:
Autolite Recommendations:
Autolite Heat Range Charts:
CHAMPION PLUG CODES:
Champion Spark plug info:
Example: J8C
J shell (14mm and 3/8 reach)
8 heat (1 Heat= coldest plug, 25 Heat= Hottest plug)
Copper Plus
CHAMPION TEMPERATURE GRAPH
500 to 850 deg C is the optimum electrode temp
CHAMPION Choices for WD and D-17 Heads:
Example: N11YC
N shell (14mm and 3/4" reach)
11 heat (1 Heat= coldest plug, 25 Heat= Hottest plug)
Standard projected nose core and Copper Plus
Autolite 306 Testing Results:
~50 hours use
Plug 1: Carbon Fouling
Plug 2: Carbon Fouling
Plug 3: Normal but slightly dark
Plug 4: Carbon Fouling
Seems to indicate that the heat range needs to be higher or mixture is too rich
Champion N9YC Testing Results:
~3 hours use
Had to run a 14mm thread chaser into head because of carbon buildup on the threads from use of the Autolite short plugs. After 3 hours on these plugs I am very happy with them. Easy starting, smooth idle, plenty of power. More later
~40 hours (22 Aug 2007)
Tractor is still running GREAT. Pulled the plugs last week and the porcelain was black like the Autolites above. I think the mixture is too rich. I will adjust. Plan to change the plugs next spring
Aftermarket
Spark Plug Wires for NON-Resistor plugs
Some of the wire sets sold for tractors are simply repackaged auto wire
kits, containing automotive type suppressive wire. The stuff is junk, no
matter how nicely colored, because it is made of non-wire material. You also
don’t need to add any more resistance to the system. So keep that stuff away
from your tractor. Order your wire
from Parts Unlimited
or you can also go to a good old fashioned auto parts store and ask for
Delco brand Packard 440 spark plug wire, which is 7mm, copper wire
used on cars in the 1950s. It comes on a 100 ft. roll, part number 1851208.
A
little about Spark Plug Wire
Car
makers add resistance to suppress Radio Frequency Interference, not in the plug
cap, but in the wire, by making the wire itself resistive, i.e.
"suppressive. The wire
is not really wire at all, but a mixture of carbon and fiberglass. It is
therefore very resistive. Unfortunately, it is also, due to the materials from
which it is made, very subject to deterioration and very difficult
to make good electrical connections with. This is why in the car world where
plug wires are used they replace those wires very frequently.
The
benefit of staying NON-resistive in your ignition system
The
benefit of doing so is two-fold. First, there is obviously one less thing to go
wrong. Ignition secondary resistors are usually carbon-based, and therefore
deteriorate rather quickly. Eliminating the resistors in these systems simply
eliminates them as a maintenance item. Second, removing the secondary resistance
often increases potential ignition coil output, because it frees up more of the
coil’s voltage reserve to be applied to the spark plug. The real-world gain is
the ability to use a larger spark plug gap, with the attendant increase in
combustion efficiency that is often realized as quicker starts, smoother idle,
and better throttle response – most of the same things high output coils
offer, but without their cost.
Edited from http://www.motorcycleproject.com/motorcycle/text/plugwiretech.html (Thanks Mike Nixon)