Timing; why is being 'dead nuts' so important?

[Barry in St.Paul]

OK, at the risk of sounding really ignorant, I'll ask this anyway; why is it so important that the timing be so absolutely perfect on a Model-A? I understand the importance OF the timing, but with a Model-A, you are constantly adjusting the spark lever anyway, and I seldom run it fully advanced even at road speeds.... So, seems the key aspect would be that the spark is retarded-enough when starting, so as not to damage the engine with a backfire...?? So I wonder, how does setting the distributor cam (ie: timing) "just right" affect engine power or anything else, since you can move the spark lever to compensate to where-ever that sweet-spot is for your engine?
It's one thing to be really anal about something like bearing-shims and such, where "they are where they are, and will stay that way!". But I don't quite get the ongoing debate about a few degrees this way or that for the distributor cam. What am I missing? Is it the "full-retard" position that is very critical, for starting? (and if so, if my engine pops off with just a turn or two of the engine, does that confirm 'good timing'?)
Just curious. Easy enough to do again and again and get "just right", but I've often wondered while I'm doing it, what difference it really makes, within reason.
thanks!

[Bob A.]

I often wonder how many model A's out there are running with absolute perfect timing.
It just doesn't seem logical that you can time it perfect just by dropping a pin in a hole compared to a timing light with a dwell meter and watching a vacuum gauge. But I guess whatever we are all doing is fine.

[Marco Tahtaras]

None of that is critical. It really serves more as a reference point and becomes more of an issue when attempting to diagnose and "compare apples with apples" in communications as we do here. It's also an important starting point when you/we are dealing with someone lacking experience and "feel". If you are going to teach someone something is it worthing teaching to do it right or is "kinda right" or "close" good enough?

[Keith True]

Marco,You're exactly right.I work on logging equipment sometimes with a man that teaches maintenance and repair of the equipment.He says he HAS to teach one way,all correct procedures,to give the kids a starting point.He says once they are out in the field they can learn how to get things done without proper tools,in the mud,without hurting themselves or the equipment.Like he told me,they need a baseline to start,then they can get out and learn how it is really done by doing it for 30+ years.There are still guys around here that will tell you that after you time the A,you start it and pull the lever down and leave it.They also line the rotor up with the headlight.They were taught that if you point the rotor at the headlight the car will run,and that is the whole idea of it.

[Bruce]

You guys sure know how to burst a guy's bubble! I get one little technical proceedure down pat -- light on, light off -- and you change the rules or say that the rules don't matter.
'Spose the same is true for front end toe-in. 1/16 of an inch. Hurrrumph.
And Prussian Blue to adjust the gears in your differential? Gotta be kidding.

[V4F]

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i think timing is important . if retarded it will heat up , if advanced it will ping , none are good for the motor . i use a timing kit so as to use a timing lite . i run mine @ 5* retard -- 35* advance . i really like the lite for getting it correct ....... steve

[Chris in CT]

Hi Barry, I think that "confluence of errors" is the answer you need to hear. Everything the guys have sent in above is, of course, true, but what they have neglected to point out is that if you collect enough small differences in the mechanical relationships within your engine, the performance will suffer. The carb will run too rich or too lean, the engine will run if the cam is one cog ahead or one cog behind the crank gear timing mark, and the engine will run if the igntion is a few degrees fore or aft of the appropriate advance for engine speed and load. But why introduce error if you don't have to? Being "stuck in the mud" on a late winter's day is one thing, but having adeqate time and equipment in the garage to do the job right is quite another. It usually takes just as much effort to do the job wrong as it takes to do the job right. Take it from someone who has tried it both ways!

[Barry in St.Paul]

thanks for the replies. That all makes good sense and I agree 100% "do it the best you can". I just wondered if there was some aspect of distributor cam position, perhaps as related to the FIXED position of points, (or something similar) that timing affected REGARDLESS OF SPARK LEVER POSITION, and I didn't realize. Again, the primary puzzlement was 'how does setting the timing EXACT, which only applies at fully-retarded position, give one more power and better running engine when the spark is advanced later?" But good replies, I hear ya all... :-) Thanks again!

[George Miller]

To me there is only one way to work on anything, that is do the best you can. Good enough is not for me. Timing is very important put it as close as you can. You can get them right on with the pin. It affects the power, gas mileage how long the engine last, plus more.

[tamagrouchy]

I would believe that if you set the timing according to any good manual, or better yet the original Ford owners manual, it will be fine. Worked for well over 82 years now. You would have to make sure to follow the directions and verify that you're setup right, but beyond that I see no real reason to get too crazy. If one was really concerned, a timing light should verify you have the minimum and maximums set correctly.

[Bob A.]

Originally Posted by Bruce

You guys sure know how to burst a guy's bubble! I get one little technical proceedure down pat -- light on, light off -- and you change the rules or say that the rules don't matter.
'Spose the same is true for front end toe-in. 1/16 of an inch. Hurrrumph.
And Prussian Blue to adjust the gears in your differential? Gotta be kidding.

You find that when you do something for a living your whole life, you find different ways of accomplishing things, and not all is like what you read in a book. Like Marco said "reference point". For example: Henry Ford didn't state "light on, light off",I just use my eyes only.. You use Prussian blue I use white lead and a dial indicator. Who's wrong who's right? They both accomplish the same thing. Don't take us the wrong way, we were just giving our opinions.

[Jason in TX]

Helps it fire a lot easier when it's cold if you have the timing just right and know where to put the lever on the column.

I agree that you can move the timing around, but for me the biggest benefit is the start up. I hate cranking and cranking my car. Nothing makes my heart start sinking more when you think it isn't going to start!

[Preacher]

" It usually takes just as much effort to do the job wrong as it takes to do the job right."

I like that.... I need to print it out and hang it so I constantly see it & try to embed it in my brain!

[Sparky]

How much should the point plate rotate at full advance (spark lever fully down?) I have a modified linkage so I'm not sure if it's moving as much as it should.

[Dave / Franklin MA]

This is from my (admittedly somewhat limited) experience. You might get by with timing that's a little off, but even the most accurate timing is useless if the point gap isn't right. The position of the cam when the points are just ready to open changes when the point gap changes, and it's important to find where your car runs the best. Specs say .018 - .022 but your car may run better if it's closer to one endpoint or the other.

On my car if I set it less than .020 I lose some top-end advance, and at .022 it runs very nicely. I'm not sure why but I'm guessing it might have something to do with the cam profile and the height of the lobes, which I assume can vary slightly from car to car. It's hard to believe all cams produced through the years are exactly identical.

Start at .018, time it, and see how the engine feels throughout the full range of the advance. Then increase it .001, retime it, and repeat until you get to .022. It's a lot of work, but you might find there's a point gap size that's optimal for your car.

[David Cockey]

Don't fuss with point gap. Set it large enough, say .022 and be done with it. If the gap is too small there is a risk that the points will arc and the ignition will not fire properly, particularly at high speeds. If the gap is too large then it's possible that the dwell (time points are closed) will be insufficient for the coil to fully saturate at high engine speeds. This can be a real problem with a V8 running at 5,000 rpm. But unless the gap is increased dramatically over the recommendations (to say .050) it won't be a problem on a four cylinder engine running at 3,000 rpm maximum.

If the car is sensitive to point gap within the recommended range then there may be a problem with the coil or condenser.

[David Cockey]

Adjust point gap first, then set timing. Point gap affects timing and increasing point gap advances the timing. Timing does NOT affect point gap. If you want to fine tune timing for some reason do it by changing the timing, not by fussing with point gap. By the way, a change in point gap affects timing by the same amount for any timing lever position.

When the points wear and the gap changes, reset it to the original setting. Timing should usually be very close to the previous setting after the gap is reset, but check it when there is an opportunity. Major wear of the block which rides against the cam can change timing if the shape of the block changes.

[David Cockey]

What is "exact" timing? Within in 1 degree, .1 degree, .01 degree or ??? Any of those are closer than makes any difference in a Model A.

Follow Marco's procedure or equivalent and you will be more than close enough.

Use one of the point the rotor type procedures and you may or may not be close enough.

[David Cockey]

Point plate should rotate 20 degrees which corresponds to 40 degrees of advance due to the 2:1 ratio between crankshaft and distributor rotation.

[Karl]

I think we overcomplicate things somewhat. In the early days of motoring timing was set roughly and fine tune based on performance . If it kicks back on starting its probably to advanced if it over heats and won't run as fast its probably to retarded. I'm sure that there are model A's out here that have been set by the book (you choose the book I use Marcos) that would run better with a bit of extra advance but since we aren't generally racing them does it really matter ?