timing problem?

[Steven B.]

Re: timing problem?

The coil contains two sets of windings, a primary and secondary, so it is not a autotransformer in the traditional sense. Autotransformers contain a single set of windings with one or more taps and are usually used to step down ac current as they will not work with dc. I've used autotransformers with a center tap in past projects.

Steve

[Gerard F.]

Re: timing problem?

William,

I use one of those setback timing lights, but is it always nice to have a vacuum gauge in line to know where you are at and be able to recognize other problems like vacuum leaks. You probably will not get the 20" vacuum at idle that I get with your engine, but that is with the vacuum advance connected. With the vacuum advance connected check the timing at maximum vacuum, and you should be in the range of 22-25 advance.

Then check the timing with the advance disconnected and plugged at wide open throttle. Initial + centrifigal should be in the range of 36-38 advance and should be all in below 3000 rpm.

I keep my vacuum gauge connected in the engine compartment all the time. If I am have problems idling, it is the first thing I check.

[Michael W.]

Re: timing problem?

The car ran just fine before the tune up and it ran just fine the day it rolled off the showroom floor in stock configuration. There's no real need to re-engineer anything at this point, just find out why it won't run properly after the latest maintenance.

[Duke W.]

Re: timing problem?

I have to fix this. I did the calculation wrong. It takes 17 mSec for the distributor to turn 1 revolution. Divide by 8 cylinders and each ignition cycle is 2.14mSec long. Dwell being 2/3 of the 45* cycle is 1.4mSec of coil charge time. Still not enough time to fully charge the coil.

Would Duke or someone please confirm that I did the calculation correctly this time? Fake data - not good.




-Dan-

I don't have time to run the calcs right now, but I can say based on the SAE papers that on an eight-cylinder engine coil saturation only occurs up to about the 2000-2500 range, but if the distributor is in good working condiiton, the single point ignition will deliver adequate spark energy and voltage up to at least 7000 revs, with the 28-32 oz. points.

Duke

[Duke W.]

Re: timing problem?

The car ran just fine before the tune up and it ran just fine the day it rolled off the showroom floor in stock configuration. There's no real need to re-engineer anything at this point, just find out why it won't run properly after the latest maintenance.

The problem is the spark advance map was set up for emission control, which severely compromised performance and fuel economy. so converting to full time vacuum advance (that meets the Two-Inch Rule) , installing lighter springs to bring all the centrifugal in before the OE 5000, and advancing initial timing to obtain 36-40 deg. total WOT advance - as high in the range as the engine will tolerate without detonation - will provide noticeable improvements.

It's all in my 2012 San Diego national convention seminar, which is an easy web search.

Duke

[Mark B.]

Re: timing problem?

The car ran just fine before the tune up and it ran just fine the day it rolled off the showroom floor in stock configuration. There's no real need to re-engineer anything at this point, just find out why it won't run properly after the latest maintenance.

Yes..this.

[Dan D.]

Re: timing problem?

The coil contains two sets of windings, a primary and secondary, so it is not a autotransformer in the traditional sense. Autotransformers contain a single set of windings with one or more taps and are usually used to step down ac current as they will not work with dc. I've used autotransformers with a center tap in past projects.

Steve

Steve, I beg to disagree with you. If the coil had 2 separate sets of windings, then the secondary would have to have a reference to ground, which it does not. That would require a separate terminal, or maybe the case if it was connected as such. That would make that terminal (or the case) hot if the connection was not made. This would not be a good setup.

If you measure the DC resistance of a coil you will see continuity between both terminals and the high voltage tower. Low resistance between the terminals and much higher resistance to the tower. That is also why coils have plus and minus labeled on the terminals, and why it is important to connect them correctly.

I have never taken a coil apart to see how it is wired, but it has to be an autotransformer. I do know they are filled with oil.

-Dan-

[Dan D.]

Re: timing problem?

I don't have time to run the calcs right now, but I can say based on the SAE papers that on an eight-cylinder engine coil saturation only occurs up to about the 2000-2500 range, but if the distributor is in good working condiiton, the single point ignition will deliver adequate spark energy and voltage up to at least 7000 revs, with the 28-32 oz. points.

Duke

HI Duke. Thanks for responding.

I believe you are probably correct with coil saturation occurring up to 2 or 2500. If saturation does occur, then the voltage will probably drop off some.

I have believed for some time that the RPM bandwidth for conventional 8 cylinder Chevrolet engines is between 7500 and 8000. Above that I don't believe this system, as designed, will provide enough spark energy to fire the plug. But this doesn't matter much as Chevrolet valve trains will limit at about 7500. So these 2 limitations determine the maximum speed that these engines can run at - in their stock configuration.

Back in the 1930s, Lincoln had a V12 and Cadillac a V16. I saw a Cadillac many years ago and I don't remember what it had for ignition, but I think it was a dual ignition system. If so, then each system had to power one bank. And I believe 6 volt systems don't have the spark energy that 12 volt systems have, but then again, those engines probably did not rev past 3500. So it worked.

This thread has wandered from its original OP question and probably should have been a separate thread. It got off on a tangent and I am at least partly to blame for that.

Your thoughts?

-Dan-

[Steven B.]

Re: timing problem?

Steve, I beg to disagree with you. If the coil had 2 separate sets of windings, then the secondary would have to have a reference to ground, which it does not. That would require a separate terminal, or maybe the case if it was connected as such. That would make that terminal (or the case) hot if the connection was not made. This would not be a good setup.

If you measure the DC resistance of a coil you will see continuity between both terminals and the high voltage tower. Low resistance between the terminals and much higher resistance to the tower. That is also why coils have plus and minus labeled on the terminals, and why it is important to connect them correctly.

I have never taken a coil apart to see how it is wired, but it has to be an autotransformer. I do know they are filled with oil.

-Dan-

Dan,

The coil has a primary winding of about 2-300 turns of a heavier wire and in the neighborhood of 20,000 turns of a very fine wire both wrapped around a soft iron core with the primary to the outside. The secondary and primary windings in the coil connect at one of the primary terminals of the coil. That is why you noticed the continuity between the terminals and high resistance in the secondary. The iron cores purpose is to intensify the magnetic field developed by the primary windings. There are two means of generating electricity (other than photovoltaic and electrochemical), one by moving a conductor through a magnetic field, and the other by moving a magnetic field through a conductor which is what occurs in a coil since there are no moving parts as in a generator or alternator. The oil in any transformer is for cooling purposes.

Steve

[Dan D.]

Re: timing problem?

Dan,

The coil has a primary winding of about 2-300 turns of a heavier wire and in the neighborhood of 20,000 turns of a very fine wire both wrapped around a soft iron core with the primary to the outside. The secondary and primary windings in the coil connect at the positive terminal of the coil (the points side). That is why you noticed the continuity between the terminals and high resistance in the secondary. The iron cores purpose is to intensify the magnetic field developed by the primary windings. There are two means of generating electricity (other than photovoltaic and electrochemical), one by moving a conductor through a magnetic field, and the other by moving a magnetic field through a conductor which is what occurs in a coil since there are no moving parts as in a generator or alternator. The oil in any transformer is for cooling purposes.

Steve

Okay, makes sense Steve because you do need two different wire sizes. But one end of each winding is connected together internally. This makes it an autotransformer when the points are open, When closed the windings are kind of in parallel, providing the ground return for both windings.

The positive terminal of the coil connects to the ballast resister. The negative side to the points.

I think we got it now.

-Dan-

[Steven B.]

Re: timing problem?

Okay, makes sense Steve because you do need two different wire sizes. But one end of each winding is connected together internally. This makes it an autotransformer when the points are open, When closed the windings are kind of in parallel, providing the ground return for both windings.

The positive terminal of the coil connects to the ballast resister. The negative side to the points.

I think we got it now.

-Dan-

I'll send you a PM with some additional information you may be interested in.

Steve

[William S.]

Re: timing problem?

That seemed to do it. When I took off the braided line that was there it turns out it was oversized and just stuck on to a small piece of the original hose. I put on the metal tube and correct vacuum lines and the hesitation is gone. Thanks for all the help.