Timing "by the book" vs. "by ear"

Ian Curtis

Ian Curtis

Senior Member
I have spent the last few weeks battling gremlins, and with a whole bunch of help from the local club we got the truck up & running for local driving. After going through just about everything else, it looks like something was bad with the practically brand new repro coil the previous owner had installed. It would throw a sizable blue spark to the plug wires, but apparently not enough to make the engine go.

Anywho, now that it drives we are onto the next adventure. After putting in the new coil, we set the point gap at .020 and timed it "by the book" (touch the cam & see the spark). On a flat road, the top speed was about 30 mph and even after a short drive the engine compartment was wicked hot.

My car came with a Marvel-Schebler carburetor, which none of us knew much about, so we suspected that maybe it was not delivering enough fuel at high :D speed. Playing with the GAV can yield a small improvement (2-3mph), but I get maybe a 1/2 turn in either direction before I start losing power or backfiring. I'm working getting a Zenith to see if this is partially the case.

After reading the books & forums, I tried advancing the timing (the tip of the rotor advanced ~3/16"), and lo and behold it got better. It seems like most people time it by the book and then fiddle with it from there until their car is happy. Top speed improved to roughly 40 mph, and the engine compartment wasn't quite so warm.

Three questions:

Can I (should I) keep advancing the timing until I don't get any more speed? Is having the highest top speed the "optimum" timing for my car's configuration?

Is the reason I have to change the timing from default to compensate for something else that isn't right? These cars seem straightforward, so I assume if everything else was "by the book" the timing would also be "by the book"?

(Kind of unrelated) The Les Andrews book says the standard SPARK gap is .035, but you may see improved performance at .045. Why does the performance improve, and what kind of performance improvement would you expect?

Thanks!
 
Last edited:
The Les Andrews book has so many mistakes that you really can't take any of it for gospel. If you set the points at .035 it most likely wouldn't run at all. I normally set my spark plug gap at .035 . If the spark plugs were set at .045 it would still run but it would strain the coil to the point that it would quickly fail . If running electronic ignition with the proper coil, a spark plug gap of .045 would probably be ok because modern cars with electronic ignition run a wider gap. I run my model A's with full advance at speed and this doesn't necessarily mean at full throttle. A lot of the information in the owners manual doesn't necessarily apply to this day and time. In the day that the owners manual was published most of the roads were far different than todays and lower speeds were mostly necessary. The octane of the fuel was so low that more retarded spark was necessary to avoid severe timing knock at the speeds that the model A could be driven. If full advance was never suppose to be used , as so many seem to believe, why was it designed with the possibility of the advance that it was designed with ??? You lose power and the engine overheats with retarded spark... If its not not knocking or bucking, why would anybody really thing that running with retarded spark was really good for the model A ??? In my lifetime most of the the roads and the octane of the fuel has been good to run at full advance at speed. The owners manual even says full advance is good at speed ... I've owned model A's since 1960 and running at full advance has never damaged a one of them The problem that most don't understand is that you will do more damage creeping along and lugging the engine in high gear than you would at full throttle. When driving at really low speed in higher gears is when more retard is needed to cushion out the buck that you would feel when running at too low of speed. Some just feel that running with the spark half way up the quadrant all of the time is good and these can't be helped a , it is just a total waste of time tring. Its similiar to the air filter on the carburetor arguement.

As far as the actual setting of the timing. The trailing edge of the rotor tip must point at the number one contact in the distributor cap with NO clockwise backlash. Any other way is just wrong !!! Backlash in the counter clockwise direction has no effect on timing. On the other hand, points gap does advance or retard timing to some degree because the spark occurs when the points open. More gap advances , less gap retards. Ford specs for points gap was anywhere from .018 to .022 and will usually run pretty good at any of these settings. When the rubbing block on the points wears and the gap begins to close to a gap of less than .018 you will begin to lose power and the engine will begin to run hotter. If the gap is set greater than .022 it won't be safe to even consider using the hand crank because it will kick back and could break an arm. Also greater gap will cause bucking at low speed and starter kickback. Starter kick back is when the timing is too advanced and when it nears top dead center the starter will strain and kick back and make you think that the battery is too weak to turn the engine. Not only will too wide points gap cause this problem but also forgetting to fully retard the spark lever when cranking the engine will cause starter kick back Optimum points gap can usually be determined at full retard. I generall y prefer slightly advanced timing for quick throttle response and set my points at .022. It is really impossible to get the timing exact with the so called modern points because the points are at a slightly different place on the upper plate.
 
Last edited:
Timing is so simple if done the original Ford way. There should be no need for timing by ear or any other experimenting.

With the timing pin in the cam gear indent, the rotor should be in this position with any freeplay to the left of the rotor. In other words you can't move the rotor clockwise by lightly trying to move it, but you might be able to move it counterclockwise as the freeplay is taken up.

When books say the rotor should point opposite the number one contact, they mean "next to". Remember in 8th grade gym class when all the boys lined up on one side of the black line and all the girls lined up on the other side, and you had to choose the girl opposite you for your dance partner during dance lessons. Same idea, opposite means "facing".
 

Attachments

  • Timing Rotor Location.jpg
    Timing Rotor Location.jpg
    66.7 KB · Views: 102
Tom-Your explanation tells me what a previous owner was thinking when I bought a roadster with the timing off by 180 degrees in the distributor! The previous owner must have misunderstood "opposite." Until your above explanation I could never understand why he would rotate the rotor as he did and hope to have a running car.
 
Tom Wesenberg said:
Timing is so simple if done the original Ford way. There should be no need for timing by ear or any other experimenting.

With the timing pin in the cam gear indent, the rotor should be in this position with any freeplay to the left of the rotor. In other words you can't move the rotor clockwise by lightly trying to move it, but you might be able to move it counterclockwise as the freeplay is taken up.

When books say the rotor should point opposite the number one contact, they mean "next to". Remember in 8th grade gym class when all the boys lined up on one side of the black line and all the girls lined up on the other side, and you had to choose the girl opposite you for your dance partner during dance lessons. Same idea, opposite means "facing".
Click to expand...

Yep Tom I always seemed to be Opposite the ugly ones ! Karl
 
Some replacement timing covers are wrong. You will insert the timing pin into the dimple in the cam gear only to find that it isn't top dead center. Check top dead center with a dowel and then check to see if the dimple is aligned with the timing hole. If there is a difference you will drive yourself crazy trying to make things work.

Timing isn't as hard as one might think, and after you have timed the engine you will only have to drive the car to feel where the engine likes to be timed. While I am driving I will get to speed and advance the timing until it doesn't seem to make a difference in the sound and performance and then I use this setting when driving. I have found that mark will change just a little each time you set the points and time the engine. I will only advance the timing fully at highway cruising speeds.
 
Tom Wesenberg said:
Timing is so simple if done the original Ford way. There should be no need for timing by ear or any other experimenting.

With the timing pin in the cam gear indent, the rotor should be in this position with any freeplay to the left of the rotor. In other words you can't move the rotor clockwise by lightly trying to move it, but you might be able to move it counterclockwise as the freeplay is taken up.

When books say the rotor should point opposite the number one contact, they mean "next to". Remember in 8th grade gym class when all the boys lined up on one side of the black line and all the girls lined up on the other side, and you had to choose the girl opposite you for your dance partner during dance lessons. Same idea, opposite means "facing".
Click to expand...

Also the points need to be just opened with the router in this position. You can use a volt meter across the points to tell when they open.
 
You can also make a test light with a couple of alligator clips, some wire, and a 6 or 12 volt light. I like to use a test light because I made one long enough to put on top of the hood where I can see it from inside the car when I'm advancing the spark lever. If you don't have a spare six volt light a 12 will work just fine (it's just not quite as bright as a 6 volt lamp may be).
 
I'd be glad to take that Marvel off your hands for you, its the best carburetor out there.

One thing that hasn't been mentioned. I hate to bring it up, but, I have to. Is the spark lever being operated correctly ? Up [10:00] to time it and for starting. Half way down [9:00] once running and most operation. All the way down [8:00] for highway speeds sometimes.
 
After setting the timing in the prescribed way, it CAN be FINE tuned by EAR!
With carb properly adjusted:
1 -With spark up it should have a smooth rhythmical sound, like, TADA-TADA-TADA-TADA!
2- With spark 1/2 way down, it should have a SMOOTH, BUT, FASTER idle.
3- With spark FULL down, it should have an even FASTER, But a somewhat ROLLING idle.
If you don't have ALL these, make minute cam adjustments, either to the advance or retard direction, until it is right. THEN, don't DIDDLE with it anymore!!
After that, with WARM engine, run at a CONSTANT 25 MPH in second gear, & adjust your GAV for HIGHEST, SMOOTHEST running & then don't DIDDLE with it ANYMORE!! Well, that's whut Chief taught me & he knew his ****! He worked part time for our local Ford Place & part time for Buddy Boggs, McCurtain County's largest NON-AUTHORIZED FORD GARAGE!
Those little CHEEP cam turning tools help, if you have OLD FUMBLY FINGERS, like me!
Bill W.
 
You must log in or register to reply here.
Back
Top