Military Vehicles Magazine OCTOBER 2019 77
or you might end up having to replace the entire engine if it
throws a rod.
Always completely drain engine coolant before removing a
cylinder head.
BIG FEET
Would putting 20-inch wheels and 8.25 tires on my M37 give
me better road speed?
Yes. However, you would lose some power; and the truck
would be more prone to breaking rear axle shafts — a fault al-
ready common on M37s.
SCHOOL OF HARD KNOCKS
What is the purpose of the little rod on the right side of the
windshield frame of my M37? — Clark T.
Try working on your M37’s engine on a windy day with the
hood raised all the way back against the windshield. The purpose
of that little rod may become painfully apparent.
NO BIG DEAL
I have seen articles on converting jeeps from 6-volt to 12-
volt, but either I missed, or it wasn’t there concerning the voltage
regulator.
I am thinking of changing mine to 12 volt for easier starting,
etc. Will the stock 6-volt regulator that came on the jeep work or
hold up with a 12-volt system? Thanks in advance for your help
with this. — Barry
You will have to change your 6-volt voltage regulator to a 12-
volt unit if you convert your jeep from a 6- to a 12-volt system.
While 6-volt regulators can be adjusted to keep an 8-volt
battery charged, they can’t be adjusted to handle 12 volts.
You didn’t say what model jeep you have. If it’s an MB or a
GPW and you want to keep its stock appearance, you can fi nd a
12-volt regulator and generator from a WWII vehicle that used a
12-volt system, such as the Dodge radio carryall or some I.H.C.
trucks.
If appearance isn’t a factor, why not just use a 12-volt alter-
nator that doesn’t require a separate voltage regulator?
You will also have to change your ignition coil from a 6- to
a 12-volt model. I recommend using a coil that doesn’t require
a separate resistor. You can keep your 6-volt distributor, though
you may have to use a different condenser. Just try it on 12 volts
for awhile, and if the points don’t burn or pit, then keep using the
type of condenser you now have.
You can also keep your 6-volt starter. In most cases, a 6-volt
starter will last longer on 12 volts than on 6.
Of course, you will have to change all your jeep’s light bulbs
and headlights from 6 to 12. Your 6-volt fuel gauge may work all
right on 12 volts, but you may want to install a step-down resis-
tor. That’s really about it for this conversion. Hope this helps.
BREAKERS FOR BEGINNERS
I enjoyed reading your article (Breaker Points For Beginners
MVM no. 125). You covered the major issues very well.
I would like to take this opportunity to amplify on some im-
portant details. This may bump the article to “intermediate”
skill level for your readers.
*When installing breaker points there are a few things one
must keep in mind. When adjusting points you are maybe chang-
ing the engine timing. If the engine was properly timed on the
last point installation, you may not have much of a problem.
When discussing this with my son, he appraised me of what
happened to a novice friend. Upon installing new points, his car
wouldn’t start.
They found that the timing had been marginal, so when the
new points were installed the timing became too far advanced.
*When adjusting points, you must consider “dwell” and
“dwell angle.” The distributor dwell is the time that the breaker
points are closed to allow the primary circuit in the ignition coil
to absorb the electrical charge. It is measured by dwell angle.
Improper dwell angle may not allow enough time for the ig-
nition coil to reach full saturation for a proper electrical dis-
charge in the secondary circuit to the spark plugs. It is important
to make sure you have the correct ignition points.
One prominent manufacturer made their points with the in-
correct angle so you could never get the correct dwell and point
gap. This is why you must have a Tach/Dwell meter to measure
the dwell angle after adjusting the new points and condenser. If
you don’t, you will run into performance problems.
*The dwell angle is listed in degrees and the specifi cations
are listed in manuals. For longevity, it is desirable to set the mov-
able point arm within the proper spring tension if possible. The
tension is measured by a point scale and is measured in ounces.
For Dodge six-cylinder fl athead engines, a spring tension of
20 ounces is acceptable. Unfortunately, spring tension gauges
are probably no longer available, so do the best you can.
*After installing the points and possible other ignition parts,
such as spark plugs, distributor cap, rotor, etc., you must time the
engine according to specs. This is done with a neon timing light.
If there is a vacuum advance on the distributor, remove the
hose and plug it. This sets the distributor for base timing. This is
done with the engine idling.
Also, by using a vacuum gauge, you can set the idle air mix-
ture to the highest and leanest setting for best performance.
Plan on investing in a timing light, tach/dwell meter, and a
vacuum gauge. With these instruments you can do a fi rst rate
tune-up and you will be rewarded with a smooth-running ve-
hicle. — Sanford Danziger
LESS NOISE, MORE FIRE?
Would spraying my M715’s fi rewall and underside of the fl oor
pan cut down engine noise a little? Also, would there be any
danger of this stuff catching fi re in the engine compartment? —
Fred Gleason
It would soften the noise slightly, but not to a very signifi cant
degree. Rubber fl oor mats and acoustic padding would work a
lot better.
I sprayed the fi rewall of a 1947 Willys pickup with under-
coating. A year later, I had to use a cutting torch when installing
a different engine! While different brands of undercoating prob-
ably have different formulas, the stuff I had used didn’t catch
fi re in any major way, even when subjected to the cutting torch’s
extremeheat.
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