The Stovebolt Site Forums The Shop Area The Electrical Bay Number 1 Distributer Cylinder Position

I am trying to determine the correct number 1 cylinder position in the distributer of my newly rebuilt '54 235. Rotating the engine, and lining up the bb with the pointer the distributer rotor points to either about 1 o'clock or 7 o'clock and I am not sure which is correct. Thanks in advance for any help.
Mike

Take all the spark plugs out.
(the engine rotates more easily with the spark plugs out)

Place a cork in the #1 cylinder spark plug hole.

Rotate the engine by hand (maybe by rotating the fan belt).

The cork pops out on the firing/compression stroke.

There are more technical ways to determine "the correct number 1 cylinder position".

Also: "Most old school mechanics would just use the finger method. Place one finger over over the end of the hose [that you have inserted into the #1 stpark plug hole], then rotate the crankshaft (clockwise is best but not essential)." (finding TDC

Thanks again Tim!

Mr. tclederman, Greenhorn question for you if you don't mind: I have seen that you are an advocate of using vacuum pressure to set optimal ignition timing. That method makes the best sense to me also (greenhorn mind you), because it takes into consideration all the variables of the particular engine.

So my question is: after you determine TDC on No. 1 using your cork method, would you then hook up the vacuum gauge and set the ignition timing?

Thank you

Just to be sure, you find TDC on the compression stroke. That is why the "cork" pops out. The other TDC is an exhaust stroke, no compression. I use a Kleenex stuffed in medium tight. There are other methods of observing valves if you want to take valve cover off.
My opinion on timing is that a timing light is sufficient.

For the benefit of this greenhorn, if you had the valve cover off, what would you look for?

Thank you

Both valves closed on #1 when BB on pointer. Turn dizzy CW until points close, then back until they just start to open. This is a "static" method.

The cork/Kleenex is with no helper.

With a helper: Just put your thumb over #1 plug hole while cranking, feel pressure and that's about #1 TDC. Turn dizzy so rotor points at #1 tower.

All these methods are just to get motor started, to begin fine tuning with a light and rotating dizzy. With the light, adjust dizzy til pointer is right on ball. Ball is already set at proper BTDC location. (proper advance)

I know a funny car driver that drove the WarEagle.

I use a grass straw from the field to check for TDC. Won't hurt anything if gets broken off, price is right, too.

Ed

Setting timing with a vacuum gauge is about as accurate as sticking your hand out the window into the slipstream to measure road speed instead of using the speedometer.

With the valve cover removed, watch the last valve in line back by the firewall (#6 exhaust). Turn the engine clockwise from the front until that spring is fully compressed, then continue turning until the spring relaxes. Just as it reaches the full-closed position, the next valve in line #6 intake) will start to open. At that point the #1 cylinder (NOT #6!) will be at the top of the compression stroke, ready for the spark plug to fire. This is an absolutely foolproof method of determining which cylinder needs to fire as the BB lines up with the pointer. The crankshaft on all 4-stroke engines turns twice in a 4-stroke cycle, so the timing mark will line up twice- - - -once on compression, and 360 degrees of crankshaft rotation later, at the top of the exhaust stroke. The spark plug needs to fire at the top of the compression stroke.
Jerry

Thanks for the explanation. So then what would you do next...

If the distributor is still in the engine block, look at the position of the rotor once you're sure the #1 cylinder is on the top of the compression stroke. The distributor doesn't care which cap tower is used as #1, only the firing order is important. Using the current rotor position for the #1 cylinder wire, arrange the rest of the wires in a clockwise direction for a firing order of 1-5-3-6-2-4. With the pointer and ball aligned in the window above the starter, loosen the screw clamp at the bottom of the distributor housing and turn the housing clockwise until the points close. Then turn the housing CCW until the points barely open. Lock the screw clamp down, be sure the rotor is in place, install the properly-wired cap, and start the engine!
Jerry

Hey this greenhorn really appreciates you taking the time to explain something which you could do in your sleep. Have a good day

When I was teaching auto mechanics at a big high school in Nashville, my students would compete in annual skill competitions sponsored by General Motors, Ford, and Chrysler Corp. There was usually a "no start" engine on a run stand included, and the kids had to diagnose conditions such as "no crank", "cranks- - - -won't start", "starts but misses", etc. One of my favorite bugs to put into the practice engine in my shop was using a piece of vacuum hose instead of a spark plug wire for either the coil wire, or sometimes for only one cylinder. With insulator boots on both ends of the hose, it looked almost identical to a high voltage wire! Sneaky, huh?
LOL!
Jerry

Yeah Sneaky, but I bet you enjoyed the heck out of watching them try to figure it out

Another trick is to plug the 12V power wire on a HEI distributor into the "Tach" terminal instead of the proper position right beside it in the distributor cap. That's a guaranteed "no start", and it makes a very effective anti-theft trick if you have to park your vehicle in a non-secure location like a motel parking area while at a swap meet, etc.
Jerry

Ok, per above instructions, No. 1 is at TDC, distributor is correctly wired and rotor pointing to No. 1 tower. Engine cranks and runs. Now I'm ready to break out the timing light for fine tuning?

"I love it when a plan comes together!" Setting the initial timing is a very simple procedure, once the mechanical principles of the engine are understood. Now comes the fun part- - - - -tweaking that initial setting for best overall performance. There are actually three timing settings, and the only one that's easily adjustable is the first one- - - -initial timing. Once the engine is running, we're partway to the goal. The next step depends on the kind of timing light you have.

A timing light works by flashing as a spark plug fires, effectively freezing the motion of the flywheel or harmonic balancer and allowing the position of the timing mark to be observed in relation to the pointer or a degree scale mounted to the engine block. The "pointer and ball" that stovebolt sixes use has a relationship that varies according to the year of manufacture and the size of the engine, but most of them align when the crankshaft is 5 degrees of rotation before the piston reaches top dead center. By simply aligning the pointer and ball with the timing light, your timing at idle speed will be 5 degrees before top dead center (BTDC). Since the window in the bellhousing is pretty wide, you can vary that relationship a little if you desire. Moving the ball to the left of the pointer advances the timing- - - -going to the right retards it. I've found that most stovebolt engines run best with the leading edge of the ball just touching the pointer- - - -not centered on it. That's probably somewhere in the neighborhood of 7-8 degrees of advance at idle.

Now comes the fun part- - - - -as the engine speed increases the spark needs to happen sooner, so the pressure wave from the burning fuel meets the top of the piston to get the right thrust on it at the most efficient point. The speed of the flame front across the combustion chamber is fairly constant, as long as the fuel mixture doesn't go lean. For now, let's assume the carburetor is supplying the right mixture. The speed of the piston is variable, so firing the plug as much as 30-40 degrees BTDC is required for best performance at cruise speed. Then there's engine load- - - - -light throttle cruise on level ground can tolerate more timing advance than when passing, climbing hills, or hauling a heavy load in the bed, or trailer towing. There are two timing advance modes built into the distributor to accommodate those situations.

Let's break this up into two posts- - - -I don't know if the forum imposes a text length limit, and old schoolteachers have a tendency to walk off and leave their mouths running! The speed-related timing advance is handled by a system of weights and springs under the breaker plate called the "centrifugal advance ". As speed increases the weights overcome the resistance of the springs and move the distributor cam clockwise, making the points open sooner in relation to the crankshaft. An advance of up to 35 crankshaft degrees or a little more can be accomplished this way. Maximum centrifugal advance usually comes in around 2500 RPM or so. Then there's a system operated by air velocity in the carburetor called "vacuum advance". Its purpose is to add a few degrees of extra advance under light throttle cruise conditions, usually 8-10 degrees. If the throttle is opened for passing, hill climbing, or load pulling, the vacuum drops and that advance goes away. Centrifugal advance is engineered for maximum power under load. Vacuum advance is there to increase fuel economy at light throttle cruise. Both the centrifugal and vacuum advance numbers are engineered into the distributor when it's manufactured, so the only practical way to change them would be to do internal modifications, or find a distributor that's calibrated differently.

There are timing lights with a "delay flash" system that allows the timing mark to be electronically dialed back to the zero point to monitor the operation of the advance systems. To do really accurate tuning, one of those lights is a must-have tool. My current light was bought on Ebay for a little under $100.00. It has paid for itself many times over! If you don't have that kind of light, about all you can do is monitor the position of the initial timing setting. There is a way to do a fairly accurate "vacuum gauge" timing, but it's done at cruise RPM with the vacuum advance disconnected, not at idle. Most people who advocate setting timing with a vacuum gauge have no understanding of what's actually happening- - - - -they're just parroting things they've heard without actually knowing what's going on in the process. That's just my decidedly biased opinion, but I can provide facts and figures to back up my Bovine Scatology!
Jerry

Jerry thanks much for all the info...very appreciated


Kevin