I recently installed a distributor in my 26 Coupe and am confused as to how to set the advance. Is there a way to actually know where and at what degrees the firing is occurring in a "T"? A chevy fires at 5-7 deg BTDC for instance. My T is starting okay and running fine but I'm all over the scale on retarding and advancing while starting and driving. How do you find a starting location to use every start and how do I know I'm not running it to retarded? Any help would be appreciated.
Set it to where, with the timing fully retarded, it fires right at or just a frog hair past TDC. Then put it in that position each time you go to start the car. Advance it from there after you get it started.
To add to what Hal said the spark occurs when the points open. With a cheap Volt Ohm Meter you can accurately time the spark.
I would start by setting the distributor so that the points open at or slightly after top dead center (piston position) with the timing lever in the full retard position. The running position for the spark advance lever would depend on many things such as does the distributor have a centrifical advance, the ratio built into the linkage, the load and speed of the engine, etc. I would guess that the maximum advance you would need is about 30 degrees at speed. I am sure others will share what they know.
When you say fully retarded are you saying the retard lever at the steering wheel all the way down?
I assume I never want to start it or drive it firing before TDC? If this is true then the full range of the retard lever is ATDC?
I'm not familiar with distributors in Ts, but the spark lever all the way up is full retard for a T running on coils and timer. You want to start the engine firing just after TDC. Once running you can advance to BTDC timing. I don't have the timing figures handy, but I'm sure if you search the forum you can find the ATDC initial retarded specification as well as the full advance figure.
Hand cranked cars should fire when the pistons are 5/16 of an inch past top dead center.
I always use a test light to time an engine statically.
Connect a test light to the wire that goes from the coil to the points and turn the ignition switch on. When you turn the engine slowly as the pistons start down the test light should come on, ideally 5/16" past top, when the points open.
that's with the advance lever in the retard position.
You can make a cardboard protractor to slip over the cap. Mark the protractor in 1 degree increments. Set the distributor fully retarded at tdc. As you advance the distributor you watch the advance as it moves against a pointer that you place in a convenient position. Note 7 deg on the distributor is 15 deg spark advance. You will probably find that you don't need more than 15 deg spark advance ie 7 to 8 deg at the distributor. If you send me a pm I can photo my protractor.
I gotta disagree with that. I believe you will need WAY more than any 15 degrees advance at highway speed. I'm thinking setting one up for the Ford specified amount ATDC is more for assuring good magneto operation. With a distributor, I see no need in doing anything other than ensuring it doesn't fire before TDC at start up. That will leave more advance for when it is needed.
If you are not familiar with adjusting the advance while running, you need to know that the faster the engine is turning, the more advanced the spark needs to be. When going down the road, adjust it for best performance. If you hear a knock, back off a little until it goes away. When you go up a hill, retarding a little will probably give you a little more "Umph". Play with it. You won't hurt anything. Just adjust it for best performance. Too much advance is probably better than too little when running. Too little can cause overheating.
In answer to your question, full retard is all the way up.
The position for starting should always be after top dead center. Top dead center can be found by rotating the crankshaft in the direction the engine turns while running, that is with the starting crank or pushing forward in high gear. Both intake and exhaust valves are closed and the piston comes up on compression to the top and then just past that point. The pin through the front pulley should be at about the 9:20 position as viewed (or felt) from the front of the car looking toward the back of the car. This should be done for cylinder #1 the front spark plug.
The spark lever should be all the way to the top of the quadrant when you do this.
After you find the correct position of piston #1 for starting, you need to determine which way the distributor rotor turns when the engine is running. Then rotate the distributor in the direction that the points just begin to open when the rotor passes the terminal on the cap for spark plug #1. Tighten the distributor so that it doesn't rotate. A test for correct setting would be, with #1 spark plug out and laying on the head, and the key on, rotate the engine slowly until you see the spark on #1 plug. Stop rotating immediately upon seeing the spark, and check the position of the cranking pin. It should be at 9:20.
Some distributors have automatic advance. If that is the case, you might not need to move the spark lever as you drive it. If it doesn't have automatic advance, move the lever as you would do when driving with the coil box and timer.
A good way to determine how to adjust the spark lever is, after starting with the lever all the way retarded, open the throttle to a fast idle and move the spark lever up and down till you find the smoothest and fastest position, then open the throttle farther and adjust the spark lever again. You will soon after driving the car for a while under various conditions, determine the best spark lever position for your particular car and distributor.
You need to determine if your distributor has a centrifical advance. An early centrifical advance distributor made for a T may require little if any manual advance. A late model centrifical distributor designed for a modern high speed engine probably won't advance fast enough and will require some manual advancement to keep up with the engine's needs.
So I will throw my 2 cents in here.
1.32 degrees of spark advance at full highway speed is generally considered the maximum and the optimum. So at 40 mph that would be my target.
2. A great way to set timing at idle is with a vacuum gauge. Adjust the timing for maximum vacuum at idle. This should probably be about mid-point on the spark lever. This was the standard way to set timing on point ignition cars in the '60's, especially Chevrolets as the outer ring of the harmonic balancer was very prone to slipping so trying to use a timing light was a waste of time.
3. If you installed a vacuum gauge you could look at while driving. This would also give you a way to gauge the spark advance setting while running down the road. OBVIOUSLY you want to have it in a position where you can see it AND keep your eyes on the road
Interesting thread. In going back to Bob Benedict's initial post, which basically relates that he is confused in regard to the proper way to use the spark advance lever, a thought occurred to me. (oh,oh,...) Hope I can explain my "thoughts" here without becoming too "wordy" as I usually do,...but here goes:
First, it must be understood that for every speed/load combination, from starting a dead cold engine, up to and including maximum rpm, with varying loads from no load at all, like idling or coasting, to the engine pulling or working just as hard as it possibly can, there is an ideal or perfect time for the spark to occur. For maximum efficiency, this ideal spark timing must change for each and every rpm/load combination. The early cars, like our old Fords, had a manual control (spark advance lever) to enable the driver to manually adjust the spark timing for maximum efficiency for the varying rpm/load combinations. It should be understood that while adjusting spark timing for maximum efficiency is desirable, it is not all that critical. Just getting it fairly close is O.K., but the closer you come to perfect timing, the better.
Now then, as automotive engineering and design improved with time, let's consider for example, the most common and typical 6 cylinder cars of the '50's,...Ford, Chevy, Plymouth, etc, it doesn't matter. By then, the engineers had developed a system for spark advance that completely took care of itself. Actually, it was two systems,...a vacuum system for "initial" advance of a few degrees when the engine is first started and then idling. As the engine increases in rpm, there is a second system built into the distributor that is centrifugal (tiny weights that spin with the distributor shaft) that actually begin to advance the spark timing even more than the vacuum system has already advanced it. The faster the engine runs, the faster the weights spin, and the more spark advance takes place. The only other important variable is that as the load on the engine increases, (starting up a hill for example) the spark timing should be retarded a bit, and fortunately, with cars of the '50's, as you open the throttle more (step on gas pedal) to climb the hill, the more the engine vacuum drops, and this drop in vacuum retards the spark timing a bit, which is just what is needed to avoid "ping" or fuel knock.
O.K., the thing to understand here is, the spark timing for the various rpm/load combinations was never "ideal" or "perfect" in those '50's cars, it was just pretty close, which the engineers figured was "good enough". And, in those days, before we became much more interested in efficiency, gasoline mileage and cleaner exhaust, it "WAS" good enough. And that's why I said that adjusting the spark advance lever in your Model "T" doesn't have to be "perfect". Because even the engineers in the "50's didn't get it "perfect" either,...just "good enough"!
Now here's the point I thought might be of help in understanding the use of the spark advance lever in a Model "T" Ford:
With the help of the "internet" on basic automotive engine operation and such, if a person can understand this very simple system of vacuum/centrifugal spark advance that was built into typical '50's distributors, I believe that all a person has to do to drive a Model "T" very well as far as the spark advance lever is concerned, is to visualize what that "automatic" spark advance system in '50's cars would be doing as you drive the Model "T",.....and try to "MIMIC" that same thing with the spark advance lever. You know that the spark must be fully retarded when cranking the engine to start; you know that at speeds ablve idle that the spark lever should be gradually advanced in proportion to the rpm, and you know that the spark should be a bit retarded with a drop in engine vacuum when the engine has to work harder, like a hill for example. And above all, finding the "ideal" or "perfect" degree of spark advance is really not all that critical! Or to put it as others have, finding that "sweet spot" is not all that critical, but with experience, you'll come closer and closer to it all the time.
Yeah, as always, MUCH too "wordy", but to anybody that actually read all my "gibberish", I really hope this might help a bit in understanding the use of the spark advance lever, and like most things about the Model "T", don't "overthink" it! Some of those "ol'-timers" really never did understand or get it right and the old Ford got them to town anyway! FWIW,.....harold
P.S. Yeah, like this isn't long enough, but if all that didn't make sense, just push the spark lever all the way up to crank start, pull it about half way down when the engine starts, pull it down farther when driving about as fast as you want to drive the car, and pull it way down when yer' goin' like hell! And when ya' start up a hill, push the lever up a ways!
Is this "bread pan" Bob? If it is, he will know what I mean. I see he is in Tennessee.
Well put Harold.
But perhaps the simplest thing is the original system running on mag. You have your pick of about 4 different settings. It's pretty easy to decide which setting is best, as there is a distinct and noticeable difference between each one. Running on battery or using a distributor, the advance is infinitely variable, within the range, and capable of being put EXACTLY where it needs to be. But in practice, one has to move the thing quite a bit to notice a difference. It usually ends up being a matter of "Whoa, that's too much and uh oh, that's not enough. Let's put it somewhere in between".
Thanks Hal,....actually I wrote that "epistle" mostly in response to Bob Benedict's original post and he did specify "distributor", and frankly, if he hadn't I'd have written nothing as my understanding of the original system running on mag is,....ahhh,....shall we say,....."severely lacking"!