Ignition and Timing

TIMING Question :
I cannot detect a detent in my timing gear with my timing pin. A recent overhaul which replaced the timing gears must have overlooked this provision. Anyway it seems I will have to locate the TDC of cylinder #1 manually through the spark plug hole. my question... which cylinder is cylinder #1? I cannot find any reference to cylinder designation in any of my literature. is #1 next to the fan or next to the firewall? thanks for clarifying.

Answer :
#1 cylinder is the front cylinder behind the fan. The detent in some of the timing gears is not very pronounced. With #1 piston at the very top of the cylinder, insert the pin in the timing gear cover and then use the fan blade to move the crank back and forth (may need to tighten the fan belt ) to locate the detent. It sometimes helps to grind a sharper tip on the pin to help locate the detent. Hopefully your timing gear was installed in the correct position with the crank gear. See the photo below to have an idea.



Question :
I have a heck of a time finding the timing detent with the timing pin. I took the pin to the grinding wheel and sharpened it a bit and that helped a little. I does seem like I always go past the detent a bit and I think it is causing me to miss on my timing a little. Does it help to remove the spark plugs so that there is no compression as you try to locate the detent? I have heard you can deepen the detent once you are sure you are right on it by the following method. It is suggested that you take a drill bit the same diameter as the timing pin and put a gob of grease on the end to catch any filings. The bit is than put into the timing pin hole and spun between the fingers. So the story goes, the metal is soft enough so that you can deepen the detent just enough so that it is easier to find.
I will appreciate your comments to the above and any other thoughts you may have toward solving my problem. Thanks very much.

Answer :
Two things you can do to find timing gear detent. Pull #1 plug to relieve some of the compression. (piston #1 is pushing up to top-dead-center on compression stroke). Turn the crank over until you reach the detent. Then tighten the fan belt and you can then use the fan blade to move the crank back and forth to perfectly center the timing pin in the detent.

The timing gear is fiber and not metal. I would not recommend drilling it. The next time you need to pull the radiator you can then remove the timing gear cover and then carefully put a bit to it. It doesn't take much. When the pin is centered in the detent, check the placement of #1 piston (look through plug hole) to make sure it is at very top of stroke (level with top of block ).



Question :
I followed the directions from the book on timing including using a light. I should say that I have noticed that there is a little free play in the distributor cam. I estimate it is equal to about half the width of the rotor tab. Because of this I don't know what part of the tab should be aligned with the body terminal.

The result of all of this is that the test light goes on almost as soon as I move the spark lever from a fully retarded position. When driving the car I find that when I position the spark lever 3/4 toward advance I getting a ticking or clicking sound. When I move the lever toward retard the clicking sound is gone.

I am really uncertain what to do. The distributor is a newly rebuilt one with modern upper plate. I also replaced the lower shaft with a new one. Les I hope you can bail me out one more time.

Answer :
I think there is an easy answer to this one. Always move the distributor cam in a clockwise direction when setting it to just before points open. Since the cam rotates CCW, the back lash will always be removed. After you make the adjustment and tighten the cam screw, move the cam clockwise (to remove back lash) to check correct positioning of the cam to the points. When you think it is positioned correctly, do the light test. Set so the light comes On at 2nd quadrant notch. You may have to reposition the cam several times to get it just right. After all this, install the rotor. The #1 distributor body tab should point at or just inside the leading edge of the rotor tab (CCW side).

After starting the car you should hear a very noticeable difference between full retard position and 3/4 down position. Test drive and see how it responds. Let me know how it goes. The amount of backlash on the distributor shaft is caused by wear on the cam drive gear shaft. A tab on that shaft fits into a slot in the distributor shaft. You may have a new distributor shaft but the wear is usually on the tab that mates with distributor shaft. CCW rotation of the distributor eliminates all backlash when the engine is running, therefore you must set timing with no backlash (CW position of cam).

NOTE: See NU-REX Nu-Wrench video



Question :
I inherited a '28 Tudor Sedan with a Zenith carburetor from my father when he passed away. The car is in really good condition and runs well, but now, after several hundred miles of "short trip" city driving, has started to backfire. It happens only after the engine is warm and after you turn the car off, even with the spark advance lever retarded, after 3-5 seconds, it will backfire that makes the whole neighborhood jump. Any suggestions? My concern is that I may be damaging the engine or carburetor.

Answer :
There are several things that cause backfire. Probability is that it is NOT your carburetor that is causing the problem. First make sure the points are set correctly at .018" and then change the condenser. This condition is usually caused by either the points being too closed (if they are burned, I would change them), or a condenser going bad. More likely it is the condenser. Let me know if this corrects your problem. Other areas to look are intermittent ignition switch and cable, and distributor lower plate rivets loose and intermittent short.



Question :
I try to start the car and it turns, but just won't catch and start running. Could it be a bad starter? Can you think of any other things I need to look at? I have absolutely no Model A experience so I am open to anything.

Answer :
If the starter is turning the engine over then the problem is not the starter. Although the starter must turn the engine over fast enough to allow the engine to start. By fast enough I mean it must crank the engine over at least one revolution every second. Assuming the engine is cranking OK, make the following checks. 1. Place a piece of paper between the points in the distributor. Then turn on the ignition key and with a volt meter check to see if you have 6 volts on the tip of the point arm. Place the + (red) lead of the volt meter to a ground point on the engine and place the (-) black lead to the Point arm. If you read 6 volts on the points then remove the piece of paper and then open and close the point arm and make sure you are getting a good spark every time the points open. If you get no spark then change the condenser.

This checks out the ignition circuit. You said you checked the timing but are not sure by what method. Here is a sure way to set the timing. But before setting the timing, I suggest you change the points and condenser set to the modern point plate. If you haven't done this already you will find it much more reliable for a car you are going to drive. Dependability and reliability is the reason for changing to the modern type points and condenser. When doing this be sure to remove the old condenser from the distributor body. See firing order in the diagram below.

Here's the procedure I use to set timing. It works every time for me and away to insure you have set the timing correctly every time.

  1. Set the points to .020.
  2. Check to clearance between the distributor rotor and each of the four contacts inside the distributor body. You can carefully bend the rotor tab or file each of the body contacts to get .025 to .030 clearance between the rotor and each contact.
  3. Set the timing pin in the timing gear cover to the detent. Remove #1 spark plug and look down the hole to make sure #1 piston at the very top of the stroke. (make sure you are observing the piston and not the valve).
  4. Set the steering column spark lever full up position (full retard). With the distributor body in place, make sure the distributor plate arm is fully against the far end of the body opening. Then pull the spark lever full down and check to see that the distributor arm is fully against the other side of the body opening. This checks to see that you are getting a full 20 degrees of advance. Now reset the spark lever full up.
  5. From the right side of the engine, the rotor should be pointing to about 5 o'clock position. Loosen the distributor cam screw and rotate the distributor cam clockwise to the point just before the points open on the lobe. Tighten the cam screw down.
  6. With the cam screw tight, try to move the cam clockwise again, i.e., remove all backlash movement. The points should be at a position just before the points open.
  7. Here is the final check. Attach a light or volt meter leads to the tip of the points arm. I made up a test light from a tail light socket with alligator clips on both pigtail wires. Clip one alligator clip to a good ground point and the other clip to the end of the point arm. When the points are closed the light is off, when the points open the light comes on.
  8. Turn the ignition key on. The test light should be off. Now slowly pull the spark lever down and count the number of detents the spark lever arm passes before the test light comes on. The idea is to adjust the points so they open (light on) as the spark lever on the steering column passes the first or second detent on the column. You may have to adjust the distributor cam several times to get this adjustment. The car should start easily with the spark lever in full up position.

With this setting, drive the car with the spark lever set about two notches from the bottom position. At 50 mph on the highway, move the spark lever to full down position for full 20 degrees advance. If the starter is turning over slowly, it will help to improve the ground connection from the battery to the starter. This is done by adding another battery cable from where the braided battery strap connects to the frame cross member, and connect the other end to one of the bell housing bolts just behind the starter motor. You will need a GM battery cable about 30" long. This will provide a better ground connection for the starter and sometimes allow it to turn faster.





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