Rotor Position Question
 

I recently read about this method of checking timing:

Remove the #1 plug, ground it against the block, and attached a wire to the plug from the #1 post on the distributor body.

Remove the other 3 spark plugs so the crank will be easier to turn. Remove the timing pin from the front cover and insert it back in the hole using the round end. Push the spark lever all the way up to the fully retarded position. Put the trans in neutral. Turn on the ignition. Take a hand crank and begin turning the engine over to allow the #1 piston to rise on the compression stroke. When nearing the top of the stroke, apply pressure with your fingers on the timing pin so you can feel it when the pin moves into the little dimple on the timing gear. In other words, you will be doing as one does when setting the timing.

The very instant you feel the timing pin slide into the dimple, you should see a spark at the spark plug!

Another reader posted a comment:

This will show you exactly when the spark occurs. The points gap could be measured and adjusted as necessary. The thing that matters most to me is where the rotor tip points when the timing pin drops into place. If the rotor tip doesn't point exactly in the correct position , the timing will be off no matter where the points gap is set.

My question is: what is that "exact correct position?" Is it when the leading edge of the rotor tab is opposite the number 1 tit or is it when the center of the tab (hence the .025 gap point) is opposite the tit?

Thanks in advance.

Re: Rotor Position Question
 

It should be positioned just like this when #1 is at TDC (pin in the hole) timing lever full retard and points set at .020".

Picture courtesy of Tom Wesenburg.
https://live.staticflickr.com/1949/4...9f2299dc_z.jpg

Re: Rotor Position Question
 

I agree with Master Cylinder's picture.

Re: Rotor Position Question
 

Rotor tip position has absolutely nothing to do with timing! Zip! Nada! No way! No how! The spark occurs when the points open, regardless of where the rotor tip is! However, rotor tip position in relation to the points lobe on the distributor cam is fixed, unchangeable. So if initial timing is off (points lobe in wrong position in relation to the timing pin/timing gear) the rotor tip position will also be off the same amount.
Remember, the initial timing setting is only in use when starting the engine with the timing lever completely up. When the engine starts and you pull the timing (or spark) lever down to your favorite setting, you have completely changed that initial setting.

Re: Rotor Position Question
 

If the piston is at TDC, Full retard, points set at .020", the points will open when the rotor is in this position.

Re: Rotor Position Question
 

..... but only on the assumption that the cam notch and the rotor arm key have been correctly and accurately located during their manufacture:). ( and as we all know there are some rogue parts out there!)

Re: Rotor Position Question
 

Whatever lug the rotor is pointing to when the points open is going to receive the charge. I agree with Master a Cylinder, the only thing that matters is when the points open in relation to the piston position. All the rotor does is direct the charge to the appropriate plug.

Re: Rotor Position Question
 

Using the spark--timing pin is outlined in the owners instruction book for checking how well you set the timing

Re: Rotor Position Question
 

Thank you! Picture is worth a thousand words!

Re: Rotor Position Question
 

Guys, using the rotor position is the same concept use with the Nu-Rex Timing Wrench. https://www.nurex.com/nu-rex-nu-wrench

Re: Rotor Position Question
 

And that your distributor bushings don't have slop or the distributor body fits securely or your upper plate fits tightly or....

Re: Rotor Position Question
 

Check out the "Distributor Cam Tool" in the Tiny Tips section of the latest Restorer Magazine (page 57).

Re: Rotor Position Question
 

That picture is a good starting point. With the points set at .020 I tweak the rotor after the initial setting driving it with the lever about midway until it responds well and goes up my little test hill near me at about 45 mph. If it maintains that speed on the hill then I'll leave it there. A little time consuming but it seems to work well and overall drive ability is good in today's traffic. I do change the timing lever at various speeds and fully retard it at a stop light. I think with a high compression head and a 330 Stipe cam, one has to set it where it is running the best.

Re: Rotor Position Question
 

The rotor position has everything to do with the timing being correctly set.


The notch in the cam is very carefully positioned in relation to the lobes. If it is not, when the points break and the spark occurs, the rotor may not be correctly positioned in relation to the conductor in the distributor body.


With the spark fully retarded, the lower corner of the rotor will be aligned with #1 conductor in the distributor body when the spark occurs for #1 cylinder as shown in the picture. If you would fully advance the spark lever, the upper corner of the rotor will be aligned with #1 when the spark occurs.


Chris W

Re: Rotor Position Question
 

I like the picture and the explanation of how he tests to get spark where he wants it. I thing the picture explains the answer to his question and most of our comments become fluff to show how smart we are, and serve only to try to outdo each other. Give it a rest, the question was answered perfectly with the picture.

Re: Rotor Position Question
 

Ouch that hurts! it is a forum and once we get goin' it's more than difficult to stop :)