Timing advance and retard

[dmdeaton]

Been trying to read and learn all I can on this subject. What is the total amount of mechanical advance with a timer? Range? Is this the same with a replacement distributor? I am talking strictly mechanical.

Thanks

[jab35]

Danny: This should help with your timer question, brief, clearly explained, and to the point. Best, jb
https://www.modeltcentral.com/support-f ... timing.pdf

[Norman Kling]

Although there is not a timing mark on a Model T, the spark is set to approx 15 degrees after top dead center on the power stroke. This is done with the spark lever all the way up. There was a tool for making this setting. The tool worked fine with the original timer. Now there are many makes of timers and the tool is not useful for all of them.
I will now describe the way I set my timing which works for all brands of timers. I push the spark lever all the way up. and with the ignition switch turned to battery, and a 6 volt battery installed, I turn the hand crank VERY slowly. I stop turning when one of the coils just begins to buzz. At that point, the pin through the front pulley should be just a little lower on the drivers side (U.S. car). This pin should be just a bit lower on the driver's side than on the passenger side. If this is not the case, the timer rod must be bent slightly to move the end where it is attached to the timer one way or the other until the buzz comes at just that point. If you are adjusting for the first time, you can accomplish this same thing with the rod detached and move the timer so it just begins to buzz when the pin is in that position.
For starting the engine, you always push the spark lever all the way up. This will cause the engine to run in the correct direction. Then with the engine running, you adjust the spark lever to the point where it runs the fastest and smoothest according to the engine speed. This can also be made while driving the car. At high speeds the lever is farther down than it is at lower speeds. With a magneto, you will find 3 and sometimes 4 positions of the spark lever where the engine will speed up as you move the lever. When running on battery, the engine will speed up smoothly with the advancement of the rod. This is normal and nothing wrong with the timer. On magneto, the spark timing is determined by a combination of rod movement and current alternations at the magneto.
If you have a distributor, The setting for starting the engine would be the same as with coils, however some distributors have centrifugal advance and or vacuum advance built into them and whether or not you move the spark lever or not would depend on the make of distributor. I personally run all my T's on magneto, so I won't comment anymore on distributors, but maybe some more familiar with Model T distributors can answer your questions.

[Steve Jelf]

This pin should be just a bit lower on the driver's side than on the passenger side.

If you think of it as a clock hand, that's halfway between three and four.

This page doesn't explain how the system works, it just tells how to set the timing: http://dauntlessgeezer.com/DG97.html

[TRDxB2]

Been trying to read and learn all I can on this subject. What is the total amount of mechanical advance with a timer? Range? Is this the same with a replacement distributor? I am talking strictly mechanical.
Thanksz

Good question: So this diagram indicates that the range of mechanical advance is 80° and the range is from 120.5° ATDC to 64.5° BTDC? If true, then it can be assumed that this is the possible operating range for solutions connected to the end of the cam shaft. Possible, because there can be limitations in Timer / Distributor designs, interference with objects preventing rotation and commutator rod set-up.

Example of quadrant positions

[John Codman]

I must confess that I don't understand the chart. 120.5 degrees is way more retard then a four-stroke gasoline engine would ever need, and most modern engines limit the advance to about 35-40 degrees. With 60+ degrees of advance I doubt that a T engine would run; if it did there would be holes in the top of the pistons very shortly. Some time ago Ron Patterson posted an excellent chart showing the proper advance and retard in a more understandable context.
In my case I never retard the spark fully because the engine simply won't start. Ron pointed out that with two or three clicks of "advance" the spark is still retarded, just not by as much. This gives a higher compression when the plugs fire and as a result a more powerful stroke. My engine loves three clicks and will start right up with no danger of it trying to turn backwards.
In my case once the engine starts I advance the spark to maximum idle RPM and then pretty much forgeddaboudit. My engine is not sensitive to timing in the sense that I do not have to play with the timing constantly. It's sensitive as hell to mixture though.

[Scott_Conger]

John

using that chart without reference to the article attached to it leads to it being interpreted completely out of context.

I suggest reading this, less you and others become increasingly confused or deceived: http://www.mtfca.com/encyclo/Ignition.pdf

As far as being able to or actually needing to advance your timing somewhat to start (and it doesn't result in a fiercely sore arm or bent starter shaft), then your timing is already set too far (incorrectly) retarded and you are compensating back to a factory "full retard" when you are pre-advancing the spark lever. With respect to having higher compression with the timing "advanced" at the column, this does not cause nor are you increasing compression. I am not trying to be mean or officious when I say that you are somehow misunderstanding what is occurring when you adjust the timer if you do. You're simply making an allowance for a maladjusted timer.

When the engine fires so late as yours does, the piston is so far down that it is true that compression is lost. If by "increasing compression" you mean that you're not losing as much compression due to not being so being severely ATDC, that would be akin to two investors buying losing a stock at different prices during the fall, and one bragging that he "made" more money than the other guy because his stock didn't go down as much.

Timing, particularly when running on MAG is not a touchy thing as many people make it out to be, so you are correct there. That said, I am highly suspicious that you have a cotter pin holding the spark rod lever to your spark rod and your car is adjusted to overcompensate for retard and likely cannot get to full advance, either. This is a common error mechanics make when they remove the riveted pin from the lever to remove and service the steering bracket bushing. For reasons known only to themselves they do not reinstall a pin but simply and loosely join the two parts with a cotter pin, and the driver pays the price for the next 40 years.

[Steve Jelf]

Timing, particularly when running on MAG is not a touchy thing as many people make it out to be...

I believe Murray Fahnestock's chart showing the spark and throttle levers in various positions would apply only to driving on BAT. Isn't timing on MAG much less nuanced? Or is the chart simply bogus?

[Chris Barker]

I agree, as usual, with Steve.
The only points of real interest on that chart are
4 deg ATDC for starting and 18.5 and 41 deg BTDC for running on magneto.

The Fahnstock charts may be of help running on battery, but are irrelevant running on magneto.

To try to answer the original question, in my view, the mechanical advance on a distributor, should you wish to fit such a thing, should allow a range from about 4 deg ATDC to about 45 deg BTDC.

[speedytinc]

Running on BAT, timing adjustment is infinite in the range. Running on MAG there are only 3 or 4 optimal node settings. Still, a full advance node is used for full cruise, back 1 or 2 nodes for hill climbing or starting out, & 1st node for starting. Murry's chart would still be pertinent, at least generally.

[Chad_Marcheese]

So by what I am seeing there, we can potentially put 64 degrees of timing BTDC into these engines? My ignition timing experience is basically with "modern" v8, and except for light cruising on flat roads, typically anything above 25-35 degrees BTDC with rattle the engine to severe detonation in most cases.....and I do realize that is a big window of ten degrees, but it typically covers most V8's.Typical flat road cruising can be around 45-55 BTC with a vacuum advance

So the fact a T has what to me seems to me is all sorts of potential available timing, kind of blows my mind a little.

[Ron Patterson]

Here is another article that will help you better understand Model T Ford "Initial Timing", the differences between Battery and Magneto operation and why you should slightly advance the spark lever during hand crank starting on the Magneto.
Ron Patterson

[Ron Patterson]

Here are the Ford recommended spark lever positions for easier starting on Magneto power only cars. I.E. no battery.
Ron Patterson

[Will_Vanderburg]

That "special" tool for setting timing on original Ford timers actually has a bend in it. The reproductions are just a flat piece of metal.