Importance of Proper Timing for Safety

[Humblej]

There have been a few posts recently about starting the engine with the timing advanced and I was surprised that some people do it intentionally. The following is with regards starting with the switch on BAT. Starting a Model T engine with an advanced spark lever could result in a broken arm or a damaged starter bendix. Here is why. The combustion in the engine cylinder is relatively slow. With a low engine speed of say 300 RPM, the engine is still turning over rather fast, 5 times in a second! To get the most out of the combustion, the ignition timing is advanced to start the explosion before the piston ever gets to TDC. So, if you are starting the engine with the spark advanced, it will fire prior to the piston reaching TDC and will try to make the engine momentarily run backwards. If it does turn backwards the hand crack ratchet will not disengage and the hand crank will swing around counterclockwise at a speed of several revolutions per second, so fast you will not even notice it. the crank will pull out of your hand and swing around and hit you hard. When using the electric starter you risk damaging the bendix in the same way.

The position of the spark lever means nothing if you have not first set your timing. Proper setting is for spark just past TDC with the lever fully retarded. This must be checked and set every time you replace the commutator. Measuring the retarded position with the ford timer gage will ONLY work if you have a Ford commutator and a Ford roller, and very few of those are still in use. The fully retarded position is significantly different for a New Day vs Tiger Timer vs Anderson Timer, Changing over from one of those to a different type and the timing will be way off.

There are those who have written that they routinely start with the spark advanced and they have never been hurt. All I can say is you may be able to clean a loaded gun without getting hurt, but I wouldn't do it.

[John kuehn]

Good information to check out! http://www.mtfca.com/discus/messages/179374/193597.html
All it takes is one time and then it will finally sink in about proper timing.

[Dan Hatch]

I was taught about this at a car show many moons ago, 1985.
A group of us T guys were sitting at a local car show when an older man approached one the cars. He let out a long line of words not suitable for kids at that car. The owner got up and said “Hang on there Pops, what’s the problem “.
The older gentleman pointed to his arm all deformed and said a car just like that one did this to me.
Story was when he was kid his job was to crank the T. One day it kicked back and broke his arm. They lived so far out in country that by time they got him to doctor nothing could be done. So he lived with it rest of life.
I learned then to double check every time.
Or better yet fix the dam starter!

[Moxie26]

Hopefully everyone will read your informative post Jeff and learn to prevent problems.

[Russ T Fender]

Are people intentionally advancing the spark to start or is their timing too retarded initially with the lever all the way up? The timing rod on one of my cars needed to be adjusted when I got it as it was too retarded with the lever all the way up. I just marked the quadrant three notches further down and used that position to start the car until I finally got the time to bend the timing rod. I must admit that it was over a year before I got around to correcting the issue and never had a kick back because in actuality the timing was correct for starting where the lever was even though it was not all the way up on the quadrant.

[Jerry VanOoteghem]

Are people intentionally advancing the spark to start or is their timing too retarded initially with the lever all the way up? The timing rod on one of my cars needed to be adjusted when I got it as it was too retarded with the lever all the way up. I just marked the quadrant three notches further down and used that position to start the car until I finally got the time to bend the timing rod. I must admit that it was over a year before I got around to correcting the issue and never had a kick back because in actuality the timing was correct for starting where the lever was even though it was not all the way up on the quadrant.

I was thinking the same thing and hoping that it is the case.

[DanTreace]

Being sure the timing is set right is something I check before helping new owners getting an old T running. Won’t hand crank until setting is known.

Plus always double check the spark lever is up on the quadrant on your own T.

Have friends who got injured by forgetting or were being distracted in the cranking moment to retard the spark.

My habit is to pull back clutch/brake lever when ending a ride, switch off ignition and then push both levers all the way up before leaving the seat.

IMG_0205.gif (121.35 KiB) Viewed 598 times

[Jerry VanOoteghem]

Imagine, if a new car was sold today, that would break the arm of its owner if simply started the wrong way...

[TXGOAT2]

A cold engine cannot kick back with the timing retarded properly. The engine doesn't care where the timing lever is, only where the timer itself is. On my car, the coils buzz a little after TDC on battery with the lever all the way up. The car starts easier on magneto with the lever down a few notches, BUT, if you get discouraged cranking on MAG and switch back to BAT, make sure you push the lever all the way back up before cranking again! I've never tried cranking my car with the brake lever in "neutral". I just don't feel that lucky. I always pull it back to firmly set the brakes.

[TXGOAT2]

"Imagine, if a new car was sold today, that would break the arm of its owner if simply started the wrong way..."

We'd probably have fewer fools per mile.

[John Codman]

Some time ago Ron Patterson in a post on this thread discussed the proper starting procedure for a Model T. He first pointed out that with the spark lever all the way "up", and everything set properly, the timing is way retarded. More then it needs to be. The piston is so far down in the cylinder when the plug fires, that much of the power stroke is lost. He suggested "advancing" the spark by a couple of notches. The spark still occurs after top dead center, just not so much after as it would be with the spark fully retarded. I adopted his starting procedure - I use three notches of "advance", and my T starts much more easily. Since the spark still occurs ATDC, there is minimal to no chance of the engine kicking back.

[Moxie26]

John... Procedure you described in most parts applies to starting on magneto instead of battery. ..... And that's after setting the initial timing as outlined in the Ford manual. Battery ignition, spark lever is fully up on starting.

[John Codman]

I start my T on battery. In fact, I have never even attempted to start it on magneto. Why would starting on battery change the ignition timing?

[TXGOAT2]

There are differences from T to T. Lots of variables, even with all new parts. The 15 degree ATDC spec probably allows a margin of safety. With 1920s gasoline and motor oil, combustion chamber carbon deposits were a common issue, and a hot engine with heavy carbon and low octane fuel might kick back even with the ignition system switched off.

[Moxie26]

John... Alternating current and direct current wave forms are different.... Ask Ron Patterson.

[John Codman]

I do understand that, but the coils run on AC. Transformers do not operate on DC. The purpose of the oscillators (buzzers) on our ignition coils is to convert DC into AC. Regardless of where the coils are getting their AC, the timer stays in the same position, and when the plug fires, it doesn't matter whether the electricity is coming from the battery or the magneto. The only real difference is that when running on Magneto, the coils get a higher voltage, and therefore give a hotter spark.

[Moxie26]

John... No comment..., maybe you need another cup of coffee.

[DHort]

Jeff,

My car has a dizzy. It is set according to Bosch's rules, but will start easier with spark lever advanced 3-4 notches I will let you explain why.

[Scott_Conger]

John, you are remembering the "advance the timing a little" advice, but applying it to the wrong starting method (it applies to MAG starting, not Battery starting). Ron Patterson has explained it so well, and so often, and he wrote a terrific article on the exact "how's and why's", that to attempt to repeat that great explanation or article has already taken too many pecks on the computer.

For those who may wish to argue otherwise, or are too lazy to research it, it can be found here: https://www.mtfca.com/encyclo/ignition2.pdf

Everyone: Please time your "T"s correctly, or learn to write with your other hand. Your doctor will want to cash the check and it will need to be legible. Jeff's original post makes a most salient point.

As for those with distributors "needing to advance it", I've run into that, too. In every instance the car had a 12V battery and a 6V starter and the engine turned over at the speed of stink and would only "chuff" and not start until the spark was advanced to the speed of the crank. One friend of mine had such a setup and while stomping the starter button mercilessly, he would pump the timing and throttle levers like a madman on a pitcher pump. The car would eventually start and he would spend half the day showing new folks "how to do it". I'd spend the other half of the day "unlearning" them.

FWIW: some of the above responses are PRECISELY why I will NEVER crank someone else's engine by hand. Period. There was one time a fellow had a failed starter on a National Tour. My dad found me and asked me to crank it. I politely refused, much to my dad's consternation. Someone finally helped out and got clobbered for his trouble. No thanks. Been there done that. It isn't too big of an ask for someone who owns a car (any car) to understand how it operates and adjust it accordingly.

[Wayne Sheldon]

AC magneto versus DC battery timing change when starting? The DC battery is flowing and active all 360 degrees of engine rotation. The AC wave form is not. There are sixteen nulls per revolution. The length of each null depends somewhat on how strong the magneto is, however roughly, about one quarter to one third of the 360 degrees will not fire the coil as it is too weak or for a moment nothing at all (the moment the AC reverses).

The reason the timing lever can be advanced a couple notches (relative to starting on battery) is that one of the nulls passes by at the starting firing point. Starting the engine is safe because the AC null will not allow it to fire until after the cylinder has gone over top center.
Then advancing the lever moves the timer such that the one half cycle earlier pulse fires the engine which then has the cylinder firing before TDC.
Minor adjustments of the timing lever have very little effect on the engines running as actual timing is largely tied to the magneto's position and strength. A stronger magneto may fire about a degree earlier due to more rapid saturation of the capacitor.

A very smart design from an era when electricity was not nearly so well understood.

The AC from a Ford magneto is very precise, however poorly tuned coils are not. One of the reasons model Ts usually run better on magneto with well tuned coils is that properly tuned coils will fire evenly relative to the AC's waveform. Poorly tuned coils will have some firing faster and/or slower, causing some cylinders to fire relatively earlier than others, resulting in uneven firing in turn a rougher running engine.

[Norman Kling]

It is not quite as critical if starting on magneto as it is on battery. On magneto, you need to turn the crank faster and the spark comes when the AC in the magneto builds up enough amps to fire the coils. However, on battery, the spark always comes the moment the rotator contacts the segment in the cap. So it must be retarded to spark just after the crank goes over top dead center or it will turn the crank backward.
Norm

[TXGOAT2]

If you are called upon to crank start a car you are not familiar with, it would be a good idea to ground the plug wires and then crank the car with the switch on Battery and observe where the crank ratchet pin is when the first coil buzzes to be sure it is past TDC with the lever up. If the car only has a magneto, ground all but one plug wire and have an assistant hold on to the plug wire and observe the crank pin for you while you crank the engine.

[Model T Mark]

I’m living proof that one should make sure the key is in the off position and the spark up prior to priming your T before starting. Any moment of the spark down for starting is an accident waiting to happen. Dislocated my shoulder and tore the ligaments off my bicep muscle in my right arm in 2020 and I’m an experienced T guy who had bad judgement one day in June. The surgeon did a good job and I did all my rehab but still hurt from the that injury. Be careful, I knew better and still got hurt.

[TXGOAT2]

Taking unnecessary risk just isn't worth it.

[John Codman]

John... No comment..., maybe you need another cup of coffee.

Maybe I do. It seems that I have written something that you are not happy with. I meant no harm or disrespect to anybody. I simply don't understand why the spark lever would need to be in a different position whether starting or driving on battery or magneto.
on magneto.

[Scott_Conger]

I simply don't understand why the spark lever would need to be in a different position whether starting or driving on battery or magneto.

...And I don't understand why it is so hard to *click* on a Club resource which explains "why" in painful detail, but one more time: https://www.mtfca.com/encyclo/ignition2.pdf

...and here: https://www.fordmodelt.net/downloads/Mo ... nition.pdf

If it's too much to read through, then the short answer to the question is: "Just Because"

[A Whiteman]

Thanks for posting those Scott, an interesting reminder and explains a lot that I only vaguely understood due to 'time to fire' delay.
Cheers
Adrian

[John kuehn]

And again.
All it takes is just one time and you’ll find out the hard way why the spark is retarded when hand cranking a T. We have to remember our modern cars and trucks do all the thinking for us when we start and drive them.

WE have to do the thinking for a Model T when we start and drive them. Its just the opposite in our modern vehicles.