I have been pondering a question for about a year and still don't know the answer. In getting a Model T running well, one of the key factors is getting the timing correct. At full retard, cylinder #1 should fire at 14.5° past TDC (top dead center). Most methods to determine this focus on measuring the movement of the cylinder descending after TDC.
I have noted that the pin in the crankshaft is horizontal, 90° off the cylinders when they are in full up or full down position. Henry and his engineers were sharp guys and looked for simple solutions to problems. If the lugs on the hand crank were set so when you pull cylinder #1 up on compression and as the hand crank reaches straight up, and then the actual position of the horizontal pin in the crankshaft was turned 14.5° past horizontal, you would have reached the proper ignition point. All that would be require to get the proper retard position would be pull the crank hand straight up when cylinder #1 is on the compression stroke. It seems to me that machining the lugs with a 14.5° turn out-of-phase with the crank handle would be an easily done process and make setting the timing an easy on the road or on the assemble-line task. Is it possible that Henry did this and I have not been able to find it in the literature? Does anyone have any ideas or is my whole theory full of errors? Doug D.
Henry and his guys never said the timing should be set to 14.5 degrees. I would not trust anything except where the spark occurs with the timing fully retarded, which should be just as downwards motion can be detected on the #1 (or any other) piston.
When the crank pin is about 3:30 - 9:30 then the crank is about 15°ATDC. It is easy to eyeball it.
Really as long as it is just past horizontal the timing should be fine. The only reason for the 15° ATDC is an extra measure of safety to set the timing with the gauge and not actually check the real timing.
Mine is set to just after TDC and the crank is at 11:00 when it fires. And, with my modified crank it is always at 11:00 and not 8:00 or 2:00.
As Royce said, Ford never said to set the timing at 14.5° ATDC. That number was reverse engineered from the 2 1/2" gauge. It is interesting to note that the article Jay posted at:
If you reverse engineer the 2 5/8" gauge the timing comes out to 5° ATDC rather then the 14.5°ATDC.
A drawback of the 14.5 degrees ATDC timing is it won't start as easily on magneto - you'll have to advance the spark lever a few clicks to get a good spark when crank starting on mag. Fortunately the magneto won't give kick backs as easily as the coils on battery
Guys, am I missing something here. The timing of the cam/crankshaft is set by the timing marks on the gears. The crank pin hole is drilled in the factory. Both are non adjustable. What we can manipulate is the timer. As this is connected to the lever on the column, by a linkage which has often been modified/bent/worn, I always just set the lever at the stop on the quadrant, the timer with the pull arm at 5 o'clock [11 o'clock on LH?]
Then I adjust the length of the control rod to suit these settings. Most times this is quite adequate. Not always is fully retarded positioned at the quadrant stop, maybe a couple of notches off. What does it matter, as we have to adjust the lever when operating the car anyway? As long as the timing is not too advanced at the stop, you are good to go.
Just another way of looking at it.
Allan from down under.
What you are describing is the "Squint Eye Method".
As long as you get it set so that it does not fire before TDC when cranking, you're good to go.
In answer to your specific question, I have never seen any Ford reference to modifying the crank pin location as you suggested.
Certainly there was a manufacturing procedure to set the initial timing, but we will probably never know what that was.
More discussion about setting Model T initial timing is in order. Service requirements for early Model T's was not well documented. I do not know when Ford started recommending the 2 1/2 inch rule for setting initial timing, but an educated guess would be around 1915. By this time Ford was making cars in large quantities and the demands of Branches and Dealers for easy service practices would have been mandatory.
I agree with Royce that Ford never formally mentioned using "15.5 degrees ATDC" to set the initial timing. But using the 2 1/2 inch rule results in the same initial timing point. For safety reasons I am no fan of the "just a bit after TDC method" as it is subject to interpretation. No doubt Royce can do this with his eyes closed because he is an experienced Model T mechanic, but the average person setting the timing for the first time could make a mistake and that could lead to serious problems.
The 9:30 and 3:30 clock face crank pin rule is good method, but the crank pin is not readily visible on the later cars with a bottom of the radiator valence.
Setting the initial timing at 15.5 ATDC is not a drawback if you follow Ford published instruction for magneto starting.
I believe Ford set the initial timing at 15.5 ATDC for safety reasons. Early Model T did not have batteries, but provision for them was made. The correct procedure for hand crank starting a Model T on magneto starting was commonly understood.
I prefer to set the initial timing exactly like Ford recommended, ALWAYS retard the spark lever for battery starting and set the spark lever as Ford recommended for hand cranked magneto starting.
Lastly there are some easy to use tools available or accurately setting the Model T initial timing.
Lang's (possibly other vendors as well, but Lang's is my vendor of choice) offers a set of rod bending tools, but depending on your seriousness in rebuilding T engines the price may be more than you're willing to give. If you only have the one car and the one engine, they also have a very affordable tool for measuring the distance between the rod hole and the fan mounting bolt. To me this seems like a "so cheap I don't know why I don't already have one" purchase. Here are the links to the tools I mean:
From what I can gather about the T engine, the length of the rod is the only variable when it comes to timing a stock T. As long as the timer and coils are wired correctly and the timing marks line up, the position of the crank has nothing to do with timing of the ignition. The position of the timer itself is the big question mark.
Timing marks ensure proper cam shaft to crank shaft timing and have nothing to do with ignition timing. The timer rod MUST be bent to position the timer properly. The timer gauge in the link above is only for use with a Ford roller timer. Others may or may NOT be timed the same. Some are definitely NOT. Do NOT rely on the timer gauge to properly set your timing unless you are using a Ford roller timer or know for a fact the timer you are using is timed just like the Ford roller timer.
This is the method I use to time My T. Works every time and can be done along the side of the road with no special tools and with nearly any timer.
Thanks for the correct 15.5° setting. I recalculated what the setting would be with the 2 5/8" gauge. If you reverse engineer the 2 5/8" gauge the timing comes out to 7.3° ATDC rather then the 15.5°ATDC with the 2 1/2" gauge.
Based on the referenced 1921 Ford Owner Dealer's write up the reason for changing was because of electric start cars. I guess it would follow that for cars up to 1919 (non-starter cars) Ford was recommending the 7° ATDC timing.
The relationship of piston position, (i.e. crankshaft travel) to the position of the timer case is fundamental to proper spark timing. On the Model T you should establish a known crankshaft position before you place the timer case in the correct location. Then you can use the spark rod bending tools to fit the pull rod to the timer hole.
As Hal pointed out, there are literally thousands of different styles of timers and the gauge may not be correct for all types. It is always good (safe) practice to recheck the initial timing when replacing the timer.
Upon looking into this closer it appears my "guess" about the date introduction of the 2 1/2 inch timer setting tool may be a bit off. The first reference I can find to the 2 1/2 inch tool is Ford Owner and Dealer magazine April 1924 Page 59. In this same article it also refers to an earlier tool ("several years ago" date unspecified) where the measurement was 2 5/8 inch and was abandoned with the introduction of the Ford Starting and Lighting System (1919) ("it was found the 2 5/8 inches sometimes caused kickbacks when starting on battery current". The second reference is found in Ford Service Bulletin Vol. 8 No. 1 page 127 Figure 316.
I like Mike's method. Why? It eliminates all the speculations Ford never mentioned that are listed in this post. Keep it simple. If it was meant to be set up by degrees there'd be a system built into the engine to do so. It doesn't exist because it's not necessary.
Make that Fordowner Magazine April 1924 Page 59.
The same reference to the 2 1/2" gauge is in the 1921 article at:
No date on the copy posted but Jay said 1921.
While I agree that method will work satisfactorily, it is just another approximate method for setting initial timing.
Based on calculations we did years ago (the spark lever is not exactly linear throughout its range of movement) this will result in the initial timing being set at approximately 8-14 degrees ATDC depending upon the number of notches you use. If you use that procedure I would recommend pulling the spark lever 5 notches down. The difference of one and a half degree is not material.
Interesting 1/8 inch at that radius results in a 7 degree timing difference. Based on my calculations that would mean the original early Ford recommended hand cranked magneto starting procedure would still be correct.
On a side note it is interesting to note it is still possible to have the engine kick back when hand cranked magneto starting, but the spark lever must be pulled far down to allow the coil to fire at 18.5 degrees BTDC. That would not happen using the recommended procedure if the initial timing was set at 7 degrees ATDC.
If anyone ever locates the "several years ago" Fordowner Magazine reference I would certainly like to know.
Your right the correct date is is April 1921 issue of Fordowner Magazine page 60.
Please make sure.....the gauge is ONLY meant to be used on FORD made timers. Every time a timing thread gets started, that gauge always gets mentioned, even in threads where it's obvious that the owner/poster isn't using a standard Ford timer.
Just a couple of tips. Before you start to set the timing make sure that the timer rod has not been all "snaked up" by tons of previous bends. If it has you might be way better off to start with a new rod since they typically are very cheap. Make sure that the rod passes under the metal tube that connects radiator to block inlet. The rod must not pass under the lower radiator hose or its clamp since that will be an interference point on a new rod. All will be sweet and easy if you have properly shortened the lower hose so that the rod is fully behind the end of that lower hose. I had to cut almost 3/4" off that lower hose to make it all correct. That is not a worry since there is ample upper hose to make it up. When you have this clearance down there then on a new rod bend the rod ONLY in the arc of the rod above the timer where it arcs down to the timer. increasing this arc width will retard your timing and squeezing this arc together will reduce the arc and advance the timing. If you start bending the rod elsewhere you will soon have a snake that doesn't work very well with travel limited by various collision points along its length and full advance or retard of timing not always possible.