The Ford Barn - timing

The Ford Barn (https://www.fordbarn.com/forum/index.php)

- Model A (1928-31) (https://www.fordbarn.com/forum/forumdisplay.php?f=3)

- - timing (https://www.fordbarn.com/forum/showthread.php?t=314658)

I was having trouble timing my Model A so a friend of mine came over to help. After insuring that the distributor was in good shape and the point gap was set at .022, he set the timing so that when completely advanced, it was at 28 degrees. Car runs great now but was wondering what the opinion was of this method of timing.

If everything is as Ford meant it to be, then the timing will be quite a bit retarded at startup. 28* at full advance is fine for most driving, but a tad low.

Timing should be right at TDC [0*] for startup and adjustable to 40* BTDC. [ which I think is too high]

So, drive it for awhile then when the points block wears and the gap closes up a bit just reset the point gap to .020" and reset the timing.

Quote:

Originally Posted by Patrick L. (Post 2140510)

Vince Falter at his seminal site www.fordgarage.com discusses the timing aspect of the Model A - and compares it to the Model B. He essentially states that if you're timed correctly you don't want to use the full 40 advance, and advocates about the 28 you propose - which is only a little less than the full range of the Model B centrifugal.

https://www.fordgarage.com/pages/bdi...toradvance.htm

Quote:

The measurements above show that the initial static Model B ignition timing point of 19 crankshaft degrees BTDC plus a maximum mechanical centrifugal advance of 17 degrees equals a theoretical geometric maximum total advance of 36 crankshaft degrees. The slots in the centrifugal flyweights limit their travel and the timing advance.
Compare this to a Model A distributor which has an initial timing point at 0 crankshaft degrees TDC plus an actual manual maximum advance of 40 crankshaft degrees (via the advance lever on the steering column). The notch in the bakelite distributor body for the arm of the point breaker plate limits the travel of the plate, and thus the manual timing advance.
The Model A ignition uses a zero crankshaft degree (TDC) initial timing point so that the engine can be easily started by hand crank, however it should never be run under load in this "retarded" position. The advance lever should always be advanced 1/3 to 1/2 travel (13 to 20 crankshaft degrees BTDC) on the steering column quadrant after starting the engine, and should generally not be run more than 3/4 advanced on the column under any normal circumstances.
The Model B is a higher compression (cylinder pressure) engine which uses more initial spark advance, and lower maximum advance compared to a Model A. This is consistent with the operation of the B engine and the need to protect it from the effects of running too far retarded or over-advanced.

Joe K

Has anyone seen a plausible theory for why the quadrant permits 40° total advance, when Ford specifically didn't design the engine to run that way? Potentially they might have designed it to span from -10 ATDC to 30 BTDC, but this isn't supported by the factory timing instructions that I've seen. Perhaps it was designed so that it could be modified to start at -10 in extreme conditions?

Quote:

Originally Posted by alexiskai (Post 2140592)

Don't forget this was Ford's first real attempt at "advance." Magnetos (Model T) is where he came from.

Ford really was "behind the times" in centrifugal or other advance. I watched the two NuRex vids on Youtube and according to him MOST other makers had made the change to centrifugal advance by the time of the Model A.

Joe K

According to Ricardo (of Ricardo head fame) the engine does not have to be as advanced with a higher compression head. I have a 5.5 head on my car so I run about 20 degrees advance with the ignition lever horizontal. That means that with the ignition lever all the way up it is retarded to after TDC. I start the car with lever down a few notches which is where 0 advance is by the timing pin. When I time the car I set the lever down those few notches and use the pin to set the points to just opening. At idle I can set the ignition fully retarded, which is after TDC and it will idle very slow at that position.

You had to fiddle constantly with the timing on a stock Model T. The operator served the function of the engine computer in a modern car. The magneto timing varies all over the place depending on the rpm.

Ricardo also said that if you are running very lean you have to have much more advance because the flame burns a lot slower. Who knows what the Ford engineers were thinking of but maybe they just wanted to cover all the bases. It could also be because of the difference in fuel back then.

If the spark advance range is a problem for someone they can add stops to limit the travel. This might be valuable if someone not familiar with Model A's borrows the car.

Quote:

Originally Posted by alexiskai (Post 2140592)

I'm not sure that Ford knew, at that time, that 27 deg was as much advance as the engine could efficiently use.

Thanks to you all for responding. I had never heard of timing this way and according to your responses, I understand the physics behind it. After timing the old fashion way (top dead center) I was skeptical about using a new system. Thanks again guys.

I have the same issue on my pickup. A Snyder 6-1 head and B cam. Have timed it so 20* is max advance. Obviously retarded on start, but no problem. Easy start, and heats up faster in cold weather. I just start it retarded and advance as soon as it gets running smooth.

the idea of maximum advance of 28 degrees was proven a long time ago to be the ideal for 4 cylinder motors. There is nothing about a model A that sets it apart from other 4 cylinder engines. It used to be that a driver of a Model A would learn how his car ran best. Nowadays people are looking for a hard and fast rule and that's unobtanium. Minimum advance at idle is very flexible. If there is a total of 40 degrees available I think it would be best to time it at 28 degrees at full advance a let the minimum be where it ends up.