Strange timing indicator...

[JimCno]

Thank you both for the information. Carla, I have already done a similar process to determine TDC (though considerably less elagent and probably less accurate). Using factory specs for timing is not really an option as under my hood is a mongrel. Parts are a mix and match combination of parts from 1935 - 1957. I've been setting the final timing by adjusting it until it runs the best.

The problem is, all the information that you gave me, as good and accurate as it is, doesn't really answer the question. When did Plymouth move the timing indicator from to the right of the "X" on the timing chain cover to the center, below the "X" of the timing chain cover?

[12905]

Jim:

Carla's advice is meticulously accurate, and is definitely the way to go to establish perfect factory marks. However, I have started many engines with the timing "close" to the specs and then used a timing light to get timing set to the factory spec (assuming the timing marks were present and accurate), but I would never rely on the marks to provide final timing. Often they are inaccurate, and many engines - especially those built 50 or more years ago - had manufacturing variations that affected final performance. In addition, factor in all the local variations in terms of climate, terrain, altitude, and the local fuels, and you soon figure out that the factory marks are a 'one size fits all' application that may not be optimum for your engine and local conditions. Hence my contention that no engine's ignition timing is correct until it has been set on the road. I think this is especially critical with the old vehicles we are dealing with. Just think of the advances in fuel technology alone, that have been made since the factory established the timing for the engine.

I support my contention with the fact that timing on modern computer-controlled engines is set and by the module taking into account all the variables I have mentioned and others as well. In addition, the timing is monitored and changed in milliseconds.

[Carla]

Jim,

Remove the 1/8" pipe plug over #6 cylinder, then use a small drill and a 1/8" pipe tap to clean the carbon out of the hole through the head, and the threads.

Make up an improvised special tool from a brass fitting with an 1/8" pipe thread end, and make a pin from a 2" approx length of round steel which will fit the bore of the fitting just loosely enough to slide freely (drill out the bore in the fitting, if needs be, to suit the
round stock you have available.

Deform the pin near one end, so that it can't slide down through the fitting. (place the pin on an anvil, place a small drill on the pin, and strike the drill with a light hammer to deform the pin slightly, for example)

Place the improvised tooling in the tapped hole, and set up a dial indicator on a magnetic base, so that the indicator will read the travel of the pin. The pin will be moved by up the top of #6 piston, when the piston travel is near top centre. Make certain the pin follows the piston down smoothly as the engine turns, a little drop of oil on the pin will help.

With all the spark plugs out, roll the engine over until the pin is as high as it will go. Set the dial gage to zero. Try this a couple more times to verify the zero reading at the highest point of the pin's travel.

Now, roll the engine over slowly and carefully, until the pin is lifted to a certain number of thousandths before the zero. The exact number is optional, such as .005 or .010.

With the dial reading your selected number before zero, mark the front pulley under the timing-pointer, using a sharp scriber or centre-punch.

Continue to turn the engine past TDC, and, carefully, bring it to your selected number after zero. Mark the front pulley as you did before.

Using a dividers, find the centre point between the two marks, and stamp a line there, using a #1 number stamp, then stamp a number 0 at the end of the line.

That is your top dead centre mark for #6 piston. Since the #1 and #6 crankpins are in the same plane, it is also your TDC mark for #1 piston.

Your engine will start and run well with the spark timed to #1 TDC. (many older Dodge truck engines are specified to be timed at TDC)

If you have a timing spec for your particular engine, say, 2deg before TDC, you can establish a '2 before' mark by measuring the outside diameter of the pulley, multiplying that dimension by 'pi', 3.1416, to get the circumference, then dividing the circumference by 360. Use a vernier caliper or outside mike to read the diameter of the pulley accurately within .005 or better. As an example, say that the pulley diameter is 9ins. 9ins. x pi = 28.2744. Divide by 360, and you get .07854. Round this to .079, which gives you 79 thou on the periphery per degree of rotation. If your timing spec is 2deg, then you will make your mark .079 x 2=.158 ( apx .002 over 5/32", for reference)

That figure will represent one degree of rotation, so double that, set a dividers to that dimension, and locate a new mark on the 'before' side of the TDC mark. Stamp a line as you did for TDC, and stamp a 2 at the end of the line. Paint a stripe of white paint exactly on that line.  I use 2 deg as an example.....check the manual for your specific engine.

To set basic distributor timing (assuming the points, etc., are all in good order), have the spark plugs out, and have a reliable helper roll the engine over with the hand crank, or by pulling on the fan, whilst snugging the fan-belt. Note the direction of rotation of the distributor as you turn the engine, and chalk a little arrow as a reminder, if you'd like.

Place a fingertip in #1 spark plug hole, and roll the engine over slowly until you feel compression, then stop when the timing mark aligns with the timing-pointer (or, if the pointer is missing, with the dial gage on #6 reading its highest point.)

The engine will be at its basic timing position, called TDC (or 2 before, or whatever advance is correct for your engine) #1 firing.

Loosen the clamp-bolt for the distributor, so that you can turn the dist body. Turn the dist body in the direction the rotor rotates until the points are certainly closed.

Now, turn on the ignition, and, being slow and careful, turn the dist body back against the direction of rotation, until you hear a teeny-tiny 'tick' and see a little spark jump across the points. Do this two or three times if need be, until you are certain you have it right.

When you are certain that the dist body is exactly where the points 'broke', snug the clamp-bolt. Put the dist rotor back on its shaft.

The rotor will be 'aimed' at the position where #1 spark plug wire must located on the dist cap. (it should be 7 o'clock, but some previous owner might have changed the position, so verify this.) With the wire to #1 plug in its correct location, put in the rest of the wires by the 'firing order', 1-5-3-6-2-4, going in the direction of dist rotation, of course. Put in the  spark plugs, connect the wires, put the 1/8" pipe plug back in, over #6.

If all else is correct, the engine will start and run normally. Verify your timing with a timing-light, and adjust as necessary.

You might get a tiny bit better performance by doing a final timing setting on the road, advancing a bit until you just begin to get the  tiniest amount of pinking on hard acceleration or hill climbing, then backing down (retarding) a degree or two.

cheers

Carla

[12905]

Jim:

There have been different covers and dampers used over the years and the positions of pointers and marks have varied. f you can determine if either the cover or the damper is original, then you can look for a mate.

In some cases I believe the keyway in the crankshaft is in line with the centrelines of Nos 1 and 6 throws and is up when they are up.? If that is the case then set the key way up, paint a white patch on the damper and use a scriber and a square to re-mark TDC on it according to the pointer you have. Then when you get the engine running, power time it on the road. Afterward, with a bit of fiddling and a timing light you can establish a new mark for ignition timing - probably about 10 deg BTDC, but you can check a spec sheet to verify that.

[JimCno]

I've just rebuilt an engine from a '57 Plymouth. The origin of it or its componants are unknown to me. It took me a while but I finally realized that the timing indicator does not match the timing marks on the vibrations damper. Does anyone know when they changed the location of the timing indicator and are there pulleys or dampers that have marks that match?