VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 spark advance question

Hello everybody,

The spark advance vacuum device of my 1940 (216 engine) was damaged and out of order. I did use a rebuilding service to get the original part repaired and am still waiting for it, but to be able to drive I did adapt a new part of FS in oregon, which I had in stock.

I have no idea how long my original vacuum device was out of order, but I guess it might be something about 1000 miles ago. Since that time I did realize there is more fuel consumption and less power.

The adapted new part works, but:
After starting the motor it pulls the distributor all the way in direction to get advanced spark.
If I grab the carburetor linkage and pull the throttle by hand there is less vacuum for some seconds and the distributor turns back to retarded position. After speeding up there is again strong and stabile vacuum and the spark gets advanced again to maximum.

In short words: As long the engine runs and there is vacuum, the spark is always advanced to maximum.
Is that the way it should work correctly?

If YES, that means more spark advance for higher RPM of the engine comes only by the mechanical spark advance by centrifugal force inside the distributor?

Who knows how it should work?

Regards
Stefangermany

From your description it is working correctly. At constant full throttle under load there will be no vacuum and the timing will be retarded. As the engine speed increases the weights in the distributor will advance the timing.

Hi Chevgene,

thanks for reply.

Now it is on me to combine and understand.
Fact is, immediately after starting the motor there is vacuum and the distributor turns to maximum advance.
This is the normal condition. More advance when speeding up happens only by the centrifugal advance system.

Means in general, the vacuum spark advance should only eliminate the previous system where the driver had to pull a knob at dash before pressing the starter pedal.

For me important to understand what the ingeneers decades ago had in their mind for drivers which are mostly to visit at graveyards today.

OK, enough of looking backwards.
Looking forward it seems I have to do a new ignition alignment or better: timing adjustment because maybe I made the last setting one year ago at a moment when my vacuum device was beginning to fail.
The logic followup must be, that my present timing adjustment is much too early. Made a short test last night after work and could not see the timing ball with the timing flash light. A clear sign that something is wrong...

But presently I have a hard work schedule and no time for timing...


Best regards
Stefangermany

Up on starting the engine the rush of vacuum when the engine starts and the throttle plate is past the idle position momentarrily the vacuum advance receives vacuum. One the throttle plate is in the regular idle position the vacuum port in the carburetor in not exposed to vaccum because it is above the throttle plate. The advance only gets vacuum when the throttle plate is open beyond the idle position.
On a 1940 the throttle is automatically opened to about 1/3 when the starter pedal is depressed. So the advance gets a shot of vaccum and when the starter pedal is released it gets none. This wasn't done for any purpose it is just what happened when they added the "automatic throttle opening" feature in 1938. It was used on passenger vars up trough 1948. Then the starter button was moved to the dash and the operator had to slightly depress the gas pedal when starting the engine.

Ya, Gene Schneider

In the "FWIW" category, last month's G&D reprinted the booklet on the 1933 Octane Selector. Aside from the general interest, I thought it was particularly noteworthy that the octane range mentioned for that time period varied from a low of 40 to a high of 78. We are burning super Ethyl from our motor's perspective.

I agree that my 1940 seems to like the "super" octane gasoline. I drove it 400 miles in one day to a tour several weeks ago. My GPS said that on the highway, I averaged 62.8 mph. I have the optional but original 3:73 gears in my 1940 coupe. It loves to cruise at 60 to 65 all day long.

dtm

Good morning Chevgene,

Thank you very much. You did show me the way to another path.

Yes, I know, timing settings and carburetor settings are together, have influence to each other. Now the weather is preparing to winter here, all day cold and wet (rainy) so it is no need of any hurry in working on the car.
You are a good teacher! In fact I was too stupid to think about the position of the spark vacuum port and the logic consequences of that position. Have to continue with work, means combined setting of spark and carburetor. I should set the timing only after beeing sure I have the conditions you wrote about (idle without vacuum advance).
Now I am able to understand the whole system and how it should work and that makes it more easy for me to find the right alignment.
But my car has more funny surprises in stock.
With my previous 1931 it was more easy. I could find the right timing wth my ears. Setting forward degree by degree until the motor begins to ping and going back until pinging is gone under all conditions and I feel maximum power and less fuel consumption.

Not possible with the 1940.
I found out it is a 1950 block with a 1940 head on it. The casting numbers say that. Checking the cars history I found out, the winter 1950-1951 was extremely cold at the place where the car was located and the block did freeze up. So they made a simple repair and did just put in a new block.
Now I have a mad combination with less compression rate than it should be and it is impossible to get the motor at the pinging point.

Have to clean the flywheel area and have to mark the timing ball with a dot of any signal colour to see it better, additional I think to make some additional marks maybe at 10 or 15 degrees earlier, just for same experiments.

Yesterday I got an email by FS my package with the repaired original vacuum advance unit is on the way now. Usually it arrives in germany within 5 days and sticks at custum up to 6 weeks after arrival. Long time, but they told me, there is too much work with forbidden fake medizines from asia and the "normal" packages must wait.

Will be patient...

Best regards from rainy germany (have been at Oktoberfest in Munich yesterday, its not far from me)

Stefan

One thing I didn't see noted above is that the vacuum line needs to be disconnected and plugged when timing the engine. Timing is done with no vacuum advance.

You didn't see it because it is not necessary to disconnect the vacuum line when setting the timing because the throttle plate is below the vacuuum port in the throat of the carburetor. Therefore the advance is not getting vacuum at idle speed.