Need help with rotor phasing

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Only the mechanical advance moves the rotor, tower position. Once the mechanical pull all the way which is about 10* at the dizzy 20* crank then the vac adv moves the pickup coil so it sparks at a different time but the rotor, tower are in a fixed place and no longer move
 
ok a little bit more explanation for the dummy in the class........
I have my spare distributor in my hand and playing with it as we speak
The reluctor and the rotor advance together.....so with a timing light, you "should" see the rotor move in or out of the...let's say the #1 post on the cap(with a hole drilled in the cap to see this) The vacuum can, moves the pickup to advance, Soooo. In my mind the rotor does not move on the cap the reluctor does...........
so say at idle and 0 degrees timing it is hitting dead nuts on the #1 post. Centrifugal advance will move the rotor to the right (same direction as rotation) to advance.(scratching my head)
The vacuum advance will move the pickup instead of the rotor causing it to fire on the other side of the post.
Man i'm even confusing myself.........
Ok it finally makes sence, and i should delete all this rubbish above, but maybe it will help someone else that is struggling with this.

Get the distributor in your hand, then it will finally make sence :BangHead::wtf::thumbsup: whooow

Now i have to go drill a hole in my distributor cap to prove that the rotor does not move with mechanical advance :D
 
The rotor does move with mechanical adv, that's the only time it moves and should be full advance at 2200 RPM. from that point on to 7000 RPM or what ever the rotor tower position does not move, but the spark timing event can change with the vac adv by moving the pick up coil.
 
so you are saying, that with a timing light, and a hole in the distributor that you will? see the rotor move in the cap with centrifugal advance?
 
I don't think you will, and that the opposite opinion i had when i got on here this morning.
 
The reluctor/ points/ other triggers the spark. THAT IS WHEN you are seeing the "light." Because the rotor moves WITH that trigger, it won't move phasing. If phasing is wrong, then either the vacuum advance mechanism is the culprit........or else the trigger/ reluctor was wrong to start with. This EG is the popular "switching pickup wires" because the trigger on magnetic reluctor is a short AC pulse, IE a positive spike followed by a negative spike. Switching the wires causes this to reverse in sequence, IE positive first, reverse wires, negative first

This reversal then causes whichever spike triggers the ECU to be MOVED in time. That is, the zero crossover point will be the same point.

Some Mopar dist seem to be out of phase, there were some selling modified reluctors to fix them. A guy has to wonder if the VACUUM advance setup is what was the actual root cause.
 
I actually bend the advance pull rod to make it longer or shorter, I have also put a piece of sheet metal between the adv and the dist to move it out. I have never cut half the tang off the cap and glued it up to move it, there are a lot of ways to get the job done.
 
The reluctor/ points/ other triggers the spark. THAT IS WHEN you are seeing the "light." Because the rotor moves WITH that trigger, it won't move phasing.
Click to expand...
"phasing" Correct, mech adv will not move it/vac adv will. mech adv shifts the rotor more CW (advancing the timing) cuz it reaches the cap terminal quicker but the phasing is unaltered. vac adv shifts the magnet CCW so the tooth reaches it earlier (advancing the timing) cuz it fires earlier which also shifts rotor phasing CCW. I think some dists just have poor quality control especially on the lower tang to top rotor clocking relationship. dig out your light/drill that hole.
 
Hole drilled in cap, white mark on rotor, timing light flashing, rpm up and down.........rotor never even twitched.
Best that i can see thru that hole(with the hood on) it's dead nuts.
The cap and rotor tell a slightly different story, but sence i don't use vacuum advance,........it good enough!!!!
Thanks to every one for the education, and thanks to downsr for starting this thread.
 
Best that i can see thru that hole(with the hood on) it's dead nuts.
The cap and rotor tell a slightly different story.
Click to expand...
& "thru the hole" is the bottom line since checking with cap off, it fires when the the reluctor "just leaves" being dead on with the magnet give or take a c hair & there is some leeway there but it is a good first test when there is a missing problem to see if it might be rotor phasing issues. we're all good in the 'hood now.
 
Running 12.7 compression and a stock ign system. Have never had any kind of problem, But have been going to do this for years. When i learned that i didn't know quite as much as i thought i did, had to break down and just do it! It's a nice piece of mind.
 
I ran the #1 piston up on compression stroke to tdc.0 degrees on the balancer. My rotor button is between #1 and # 8.Could this be my problem. Do I need to re-clock my oil pump
 
Your not running at 0* so set your balancer at 30 and see were the rotor points, and turn the rotor so the weights are out and see were it is.
 
downsr said:
I ran the #1 piston up on compression stroke to tdc.0 degrees on the balancer. My rotor button is between #1 and # 8.Could this be my problem. Do I need to re-clock my oil pump
Click to expand...

This tells you absolutely nothing as it varies with timing setting. There is only two things that matter..........where the points/ reluctor triggers the spark and where the rotor is when that happens. You simply need to check with a timing light.......which flashes when the spark triggers.......and see where the rotor is by the light.
 
Downsr..... may I ask if the kickback occurs immediately when you start cranking, or at some random time after you have started cranking, or when you let off the key and stop cranking? And what ignition system did you have in there before?

In reading your descriptions of how you have checked this, it sounds like the rotor is about 14 or 15 degrees of crank rotation past the center of the desired spark post and heading towards the next cylinder's post in order when it fires. And while I agree that rotor phasing is not a normal cause of starting kickback, let's all remember that this is an MSD and at low RPM's will generate several sparks in succession. The lower the RPM, the more successive sparks will be created. Per MSD instructions sheets, these sparks supposedly last for 20 degrees of crank rotation. So in Downsr's case, the last spark will come at around 35 degrees of crank rotation of the rotor past the center of the correct spark tower.

So with that late rotor phasing, there is indeed some possibility of a later spark occasionally jumping to the next cylinder in order, which may fire that next cylinder's charge. That next cylinder won't be up on the compression stroke by the time that last spark in the spark train comes along but it will fire what charge is in there. That might cause mild kickback, as part of the expanding burnt charge will be trapped in that next cylinder as it tries to come up on the compression stroke. It would also spit back through the carb.

This may also explain the observation of the spark pits on the tower contacts all being towards the 'late' side of the contact; IMHO, this is a valid observation in this particular case.

The suggestion to modify the rotor mounting or cap mounting for better alignment and run it like that for a while, are the best suggestions to confirm or deny that this is the problem. If you retard the timing, it may or may not solve the issue unless you know it back at least 10 degrees IMHO.
 
It has a msd 8388 distributor with vacuum advance.If the cars sits over night after driving it that day.The first time i try to start it it will kick back from that point on it will not kick back.If i let it set overnight and use a remote starter the first time i turn it over it does not kick back.Only kicks back when i use the ignition after sitting overnight.It looked like when i had intake off it had a lot of unburned fuel on top of valves also on top of pistons.Looked inside cylinders with camera.So i went from a 750 to a 670 holley thinking it is getting way to much fuel.Same thing.So it seemed to be ignition related when it fires.Took cap off a saw how it was firing on the plug towers. That's why i started looking at rotor phasing.When i rotate the engine around by hand my rotor is directly lined up with the #1 tower at 40 degrees btdc. At 0 degrees on the crank it it sitting between 1 and 8 towers.I am going to do some more checks on it when i get off work. If
i put timing light on it at 800 rpm it is at 22 .Mechanical does not start till 1200 rpm and vacuum is disconnected.Any help is appreciated and for everyone who has repled i an listening and trying what your are suggesting. Msd must have a had a problem with phasing or they would not have made a adjustable rotor cap.
Also it has 175 psi compression which really makes it kick back
 
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Well let's think about this, 20* of crank rotation is 10* of dist rotation and the posts are 45* apart at dist 90* at crankshaft. 10* of dist rotation is not enough to get it close to the other post.
 
The other thing that "might" be......and there are various issues with this..........

is that the thing is "false" triggering for some reason..........either a problem electronically in the unit, or due to some EMI/ RFI problem

Don't you have "some other" ignition you can slap in there long enough to see if you can get a baseline?

Have you at this point actually checked the dist for proper phasing?

(Point that out if I missed it.........)
 
I am not sure if i am cking it correctly.I turned the engine by hand. On the compression stroke on number 1 cylinder the rotor was pointing at number 1 on the cap when the balancer was at 40 degrees . Continued to rotate balancer to 0 degrees the rotor is between 1 and 8 posts on cap. I thought at o degrees on the balancer the rotor would be lined up with number 1 on the cap.I cut a square hole in the front of the cap so i could see the rotor and the posts on 1 and 8 when i was doing this.I can put a timing light on it and see it is firing on the trailing edge of the post on number 1.Am i cking the phasing correctly.This type of dist is a ready to run and does not use a box.
 
67Dart273 said:
The other thing that "might" be......and there are various issues with this..........

is that the thing is "false" triggering for some reason..........either a problem electronically in the unit, or due to some EMI/ RFI problem
Click to expand...
That was my thought too, Del, which is the reason to ask exactly when it did this. Since it only happens once, and when the ignition switch is first used, I am beginning to suspect this type of problem. Downsr may have given a good clue in his last post above.

A momentary dropout in the voltage may make the MSD distributor 'hiccup' (or the ignition box), and the use of the ignition switch may cause this voltage drop if the ignition switch has high resistance, like they get when old. The remote start would be set up to bypass the regular ignition switch and being newer, is probably a good low resistance relay, and would not have the same issue.

Downsr, does you have an MSD box with this, or just a regular Mopar box? I may have assumed the wrong thing in my last post.

And is the ignition switch old?
 
It does not use a box or ecu unit it is a ready to run version msd dist.The switch is an original in 70 duster .
 
OK, understood. I am just taking a shot in the dark about the ignition switch based on the fact that the remote start does not do this.
 
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