Distributor timing

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Model T Ford Forum: Forum 2017: Distributor timing
Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Lay,,,,,,,,,,,,,,Lancaster Ca. on Thursday, January 05, 2017 - 08:38 pm:

My car had a distributor on it when I got it. I want to make sure it is timed right. I set #1 cyl at tdc on compression and the rotor is pointing at # 1 spark plug ( on the cap ). The spark advance will move the dist. in the advance direction from there. When I run the car there is a distinct deference from full retard to full advance. My car seems to run good I just want to be sure. Does this sound good to you? Its a 26 roadster.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert L. Cook on Thursday, January 05, 2017 - 09:22 pm:

Yes. sounds good.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Lay,,,,,,,,,,,,,,Lancaster Ca. on Thursday, January 05, 2017 - 10:28 pm:

Thanks Rob.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Duey_C on Thursday, January 05, 2017 - 11:48 pm:

When that rotor crosses the terminal in the cap, the points should open just after the piston passes top dead center. Fully retarded, of course.
I've used a multi meter on mine to see/make sure when this happens.
The coil has been charged and will give a spark just after TDC.
The T I have that has a dizzy (distributor) on is plum wore out so it doesn't really like the spark lever much past half way down. YMMV. :-) I've a TTP dizzy from almost 20 years ago.
Some fellows prefer a spark 14 degrees after top dead center.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Friday, January 06, 2017 - 07:27 am:

"Does this sound good to you?"

Well, it depends. At full retard, does it spark just before or just after TDC. Just after sounds good to me. Just before? Under the right conditions, that could break an arm or starter bendix.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, January 06, 2017 - 08:16 am:

Agree with Duey and Hal - you need to make sure the spark event happens just after TDC, with the crankshaft past the tdc so that when the points open and the coil discharges the piston will force the crank to rotate forwards, not kick back.

The best way to check this is with an ohm meter on the points, battery disconnected. Rotate the engine, watching thru the spark plug hole as the valves both close as the #1 piston comes up on its compression stroke. At the same time the distributor rotor should be approaching the #1 position. Watch for the points to open exactly at the point where the piston starts downward as indicated by the ohm meter going to "open" or "infinity" resistance.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman - Sumner,WA on Friday, January 06, 2017 - 01:35 pm:

O.K.,....here's something you've probably never heard, and maybe that's because I'm wrong, but "here's my story, an' I'm stickn' to it!"

I think "distributor timing" or, "ignition timing" is over-rated in a Model T or Model A Ford, and here's why:

In a more modern distributor ignition vehicle, say,....cars of the '40's, '50's, '60's, etc, most ignition systems were designed in such a way that ignition timing was basically determined by a combination of two things,....initial spark advance on engine starting by immediate vacuum advance due to vacuum diaphragm mechanism which immediately advances spark on engine start-up. Further spark advance was gradually increased with increasing engine/distributor rpm via centrifugal force actuating weights attached to distributor shaft.

It should be noted that the amount of total spark advance for any given combination of rpm/engine load was determined by the combined effect of vacuum diaphram/centrifugal weights systems engineering design. It should also be noted that for any given engine rpm and load combination, the amount of spark advance was not exactly perfect, but close enough for "reasonable" fuel economy and engine performance as determined by engineering design.

Now then, all engines, whether spark advance is determined by automatic combined vacuum/centrifugal systems designed by engineers, or, manually determined by the car's driver as in Model T and Model A Fords, all engines have a perfect "sweet spot" for ideal degree of spark advance.

In the more modern "automatic" combined vacuum/centrifugal spark advance systems, the degree of spark advance is "approximate" but seldom the perfect "sweet spot". In the manually driver controlled spark advance in the Model T or Model A, the degree of spark advance is also seldom "perfect" as it is totally dependent upon the drivers "seat-of-the-pants feel" of the engine's performance at any given car speed, engine rpm/load.

All of this to say that no matter how "perfectly" the Model T or Model A ignition is precisely timed, really, the only thing that such "precise" timing adjustment does is move the perfect "sweet spot" a few degrees towards a bit too advanced, or, a bit too retarded. The "sweet spot" is always there somewhere, but it totally depends on the skill and what I call "seat-of-the-pants" FEEL of the Model T or A driver to set it "PERFECT", which in my estimation, almost NEVER happens. There are some pretty good Model T mechanics that merely retard the spark for starting, and then when driving away, just pull the spark advance lever down to where they think is enough! So that usually being the case, what's the advantage of such absolutely "PERFECT" spark timing in the Model T or Model A? Most drivers can't find it by adjusting spark advance lever anyway! They "guess" at it, or, worse yet, just pull the advance lever down and forget about it!

Again, that's my story, an' I'm stick' to it! FWIW,......harold (:^)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman - Sumner,WA on Friday, January 06, 2017 - 01:43 pm:

Okay,...I should "shut up" as I've been too "words" already as usual. However, in proof reading my "epistle", and re-reading this thread, I believe Royce said all that is really necessary in that first three-line paragraph in his post. As Royce said,...."make sure the spark event happens just after TDC...."

After that, the "sweet spot" for the spark advance lever is someplace part way down the quadrant,......get enough driving experience with your "T" and you'll find it!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Harold Schwendeman - Sumner,WA on Friday, January 06, 2017 - 01:45 pm:

.....too WORDY,.....dang it! Stupid "auto correct"!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Lay,,,,,,,,,,,,,,Lancaster Ca. on Friday, January 06, 2017 - 03:06 pm:

Ha ha ha. Thanks everyone. I appreciate ALL the feed back. Good stuff. Thanks.


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