The Stovebolt Site Forums The Shop Area Engine Shop Anyone ever used the ACTRON Volts/Dwell/RPM Meter on a 6 Volt Setup?

I have a 1948 Chevrolet 1/2 Ton Truck with 1962 235ci engine on a 6 Volt Setup.

Using the ACTRON Volts/Dwell/RPM meter -anyone ever used this on a similar 6V setup? For RPM reading is the correct application, GREEN Clip on (-) Negative Ignition Coil terminal, and BLACK Clip on Engine Ground?

Appreciate any feedback!

No feedback from me, but 0-16v and around $25 looks appealing.

Let's hope someone post advice/experience.

Found this on-line (it might help you?):
"Question: How Do You Connect It To The Engine
Answer: There is a ground connecting wire to be grounded to battery or engine, and connecting wire that will be connected to Points, distributor, or to power out put on alternators or generators."

The instruction manual is supposedly at this link.

I read the poorly worded/edited instructions the same way you do:

green clip to the negative terminal on the coil (negative ground system?) - diagram shows coil lead to distributor
black clip to battery ground (negative on Chevrolet)

Thanks Tim! I went ahead and ran it, it works! The black clip to engine ground and the green clip to coil (-) negative terminal that is also wired to the distributor.

So a follow-on question, the shop manual says to drop Idle to 500 RPM and then run the vacuum test. But in terms of regular Idle setting (day to day operating) , seems like 800-900 RPM is a much smoother, stable idle. Do you have a 235ci in any of your trucks? Just curious, what do you set the Idle to?

As long as the engine doesn't try to "run-on" when the ignition switch is turned off, idle speed can be set pretty much where you like it to be. Idle speed that's too high can cause an engine to "Diesel" from compression ignition which can damage pistons, etc. Above 800 RPM, you're probably going to be getting into the intermediate fuel range between idle and high speed, so the idle mixture screw adjustment might not be very effective.
Jerry

Took your advice, and it's sounding great!! Disregard what I said about 800-900 RPM. Using this ACTRON Tach meter, I just dropped it down to the specified 500 RPM (via the Throttle screw) and then adjusted the Idle screw (counter clockwise, letting it out some) with an eye on the Vacuum gauge and I could see the dial going higher on the Vacuum, from 15 going up to 17-18 in/Hg with each turn I was letting out the Idle screw. Basically, as the Vacuum increased, (holding at 500 rpm), the engine sounded better and has a much quieter, smoother hum to it. Many thanks Jerry & Tim.

With the valves adjusted properly and good compression on all cylinders, these old engines will slow down until you can almost count the fan blades and still run smoothly. A long stroke, a big, heavy flywheel, and close to a hundred pounds of crankshaft working together has enough inertia to keep on turning at some really slow speeds.

There's the remains of a big single cylinder stationary Diesel engine at a closed-down cotton gin in Hazel Green Alabama. The flywheels are something like 8 feet in diameter, cast in pie wedges and bolted together, and the stroke is about 3 feet. Its normal running RPM was around 300 or so. Idle was about 60 RPM!

Something like this:



Jerry

I try to set my idle as close to 450rpm as possible (maintaining a smooth idle), 450-500rpm is the spec.

.

Basically, as the Vacuum increased, (holding at 500 rpm

This does not make sense to me. Increasing vacuum
but rpm stays the same.

Using the idle speed screw set the idle speed to 500 rpm 1st.

Then adjust idle mixture screw to get the highest rpm.
Do not leave the mixture screw turned past the point
where the highest idle speed was reached. You
will just be wasting fuel and increasing the amount
of gasoline to get into the crankcase to dilute the oil.

Then readjust the idle speed screw to reset the idle
back to 500 rpm

Then see if you can increase the idle speed again
by readjusting the idle mixture screw again to
see if you can get the idle rpm to increase.

Then readjust the idle speed screw to bring the
idle rpm back to 500 again.

Your carb is now zeroed in.
Jeffrey

Thanks Jeffrey, appreciate the info. So the Shop Manual indicated (step 3) to set idling speed to 450-500 RPM by adjusting the stop screw on the throttle lever. Then (step 4) to turn the idling screw Left or Right, until your gauge reaches the highest Vacuum, which should be between 17-21. I found that turning to the right, the engine started to stumble, but turning it to the left (counter clockwise) raised the vacuum.

Turn the mixture screw left/right until higest vacuum.
Then re-adjust the idle speed.

What manual did you use?

It's the 1948-53 Shop Manual. Yes, after (step 4) adjusting the vacuum with idling screw, (step 5) in the manual says to re-adjust idling speed, if it changed, via the stop screw on the throttle lever...

Tim, ran some [dry] compression tests, are these numbers alright?

Cyl #1: 120 psi
Cyl #2: 118 psi
Cyl #3: 115 psi
Cyl #4: 115 psi
Cyl #5: 118 psi
Cyl #6: 120 psi

You are right, but I'd say step 4 is wrong.
http://chevy.oldcarmanualproject.com/shop/1948_51truck/51ctsm0620.htm

Unfortunately, the 1954 manual does not use the same technique (no use of vacuum reading).
http://chevy.oldcarmanualproject.com/shop/1954truck/54ctsm0652.html

The 1947 manual is more like the 1954 manual.
http://chevy.oldcarmanualproject.com/shop/1947truck/47ctsm0648.htm

Here is the carburetor/timing tuning technique that I use. It can be argued that this is not optimum, but it is close enough and it is easy.

Wait to hear from others, but I would be very satisfied with those readings, especially since they are so close to each other.

The Shop Manual says 110 +/- 10 lbs

That's very interesting, the changes in the manual from those years. Wonder why?

Did you get a chance to see my compression stats, they alright?

Yes I did. Check the post above.

Super, thank you sir!