OK, Gearheads!

LubeDude · Jun 1, 2005

Re: OK, Gearheads!

I have not had the time to get it back together, I had to work on one of the apartments for a couple of days. The only other things I am doing is running the valves and putting on a new fuel pump which I have had forever, but now with the A/C removed, it is the time to do it. So far I have only adjusted the valves on the passenger side and they were all a bit lose. When I put on the new coil, it would still arc out of the top, but when I put on the coil wire, it didnt, so there is a change there.

dogsdad · Jun 2, 2005

Re: OK, Gearheads!

Skinnywater, your point that the engine raps up to 6000 strongly does perfectly contradict my statement that the coil should never fire a plug. My mistake. I think I must have had my mind in multiple-coil mode or something. Obviously the coil WILL fire a plug, or we'd be at about zero RPM or so. Duh. I would assume that since we're looking at a 327 that it has a conventional breaker ignition. I've always believed that plugs are fired at about 50kV...or am I thinking of HEI?? I really am not so sure the more I try to recall. But, I do think that the coil's primary will actually see a larger voltage swing than 12 volts---for two reasons. First, the ignition system voltage should be closer to 13.5 or thereabouts. Second, and more importantly, because of the inductive "kick" the primary would produce, there will be a tendency toward a bit of self-induction, which essentially would cause the voltage change seen by the primary be greater than system voltage. The same thing would be seen in the secondary, only about 150 times greater in magnitude (if the 150:1 ratio is indeed correct). I can only guess what the end result would be, but I think it would be considerably more than 18kV being sent to the rotor and plugs. By your statement pertaining to mixture density at 6000 rpm, I am assuming you are referring to the compression increase due to ram effect? I think "dynamic compression ratio" is the idea here... I think the fact I wanted to illuminate is that when you see that kind of thing happening on a coil without the connection to the plugs (via distributor, of course---I ain't totally unconscious

), you can't expect that voltage to see the plug gap as a path of less resistance to ground, reliably, under load or at higher rpm. I think I understand why you say the multiple spark paths "un-indicate" a carbon track. Since you pointed that out, and I have thought about it, it seems more like it...uhhh, hmmm. I dunno, really. What would cause it to behave that way?? DIRT? I would think there's got to be someTHING there serving as a conductor!? Inquiring minds, ya know. -dd- -dd-

kenimpzoom · Jun 3, 2005

Re: OK, Gearheads!

I think the stock coil output is around 30,000 volts. Also remember the primary wire volts are lower due to the "resistor wire". I am thinking somewhere around 8 volts??? Ken

dolluper · Jun 3, 2005

Re: OK, Gearheads!

From Pertronix To determine if your systems coil is compatible with the Ignitor, some measurements should be taken prior to installation of the Ignitor. Caution While performing this test, never leave the ignition switch on for more than 30 seconds at a time. Set your voltmeter to a 15 or 20-volt scale. Attach an 18 or 20 AWG jumper wire from the negative coil terminal to an engine ground. Attach positive (red) lead of your voltmeter to the positive side of the coil, and the negative (black) lead to an engine ground. Turn the ignition switch to the run position. Now read the voltage at the positive coil terminal. Turn the ignition switch off. If the voltage measured is approximately 12 volts, no resistance wire is present. A typical resistance wire will provide 9 - 6 volts. The next step is to determine the resistance in the primary ignition. Label the wires attached to the coil terminals and note their appropriate location. Make sure that the ignition switch is off and disconnect all wires from the coil. Adjust your meter to the lowest ? ohm scale. If you are using an analog style meter make sure to zero the needle. Measure from the negative terminal to the positive terminal. Write your measurement down. Now the maximum system amperage can be determined, divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage. Four cylinder engines should not exceed 4 amps. Six and eight cylinder engines should not exceed 8.5 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor. Example Voltage 12 Resistance 1.5 12 / 1.5 = 8 Total amperage 8 Click support here http://www.pertronix.com/

dogsdad · Jun 3, 2005

Re: OK, Gearheads!

The Pertronix website shows some cool stuff. Makes me wanna trade in my '98 for a '68! The procedure that dollupper has posted appears to be what's necessary to keep from overloading the Pertronix aftermarket electronic ignition module. The ballast resistor is meant to add resistance to the primary circuit in case the coil being used does not offer enough resistance all by itself. That's not hard to understand. But with conventional breaker points, there's nothing the coil can overload but the points themselves. I remember messing with some of my first cars with breaker-point ignition, and I never saw a ballast resistor on any of them and if any of them had resistor-wire on the coil's primary circuit, I was never aware of it. Did they all have that??

Skinnywater · Jun 3, 2005

Re: OK, Gearheads!

A couple of things. A freshly tuned engine typically uses only 12-15KV to fire the plugs. Maximum coil output occurs when there is a problem in the secondary, as in LubeDudes picture, an open coil secondary tower. And if memory serves me, isn't the primary voltage resistor bypassed when the starter is engaged on that vehicle? And here's something that might be useful. http://www.bgsoflex.com/igncoil.html

LubeDude · Jun 3, 2005

Re: OK, Gearheads!

Originally posted by Skinnywater: And if memory serves me, isn't the primary voltage resistor bypassed when the starter is engaged on that vehicle? And here's something that might be useful. http://www.bgsoflex.com/igncoil.html

Yes it is, and especially when you are using a remote starter switch.

dogsdad · Jun 3, 2005

Re: OK, Gearheads!

That's a great webpage, skinnywater. It shows that spark voltage is much higher at low RPMs, but falls off as RPMs increase. Now what you're saying makes sense to me. I always just accepted that dwell time was to be set at 30 degrees. I wonder why no one ever designed a centrifugal mechanism to increase dwell time as engine speed increases, kind of like like centrifugal timing advance. Or has someone already done it?? What has occurred to me even as I type is that it would be somewhat more complicated because of the fact that if dwell was changing on the fly, then it would be affecting the ignition timing to some degree even without the action of mechanical advance. Hmmm... Anyway, I doubt anyone would bother, at least now because now we have elctronics that can do all that, probably cheaper and better. I still am wondering about the ballast resistors I could never find, and the resistor wire I never was aware of... -dd-

Skinnywater · Jun 3, 2005

Re: OK, Gearheads!

It shows that spark voltage is much higher at low RPMs, but falls off as RPMs increase.

Yes, at low RPM's the saturation time of the coil is greater. The higher the RPM the saturation time substantially decreases.

I wonder why no one ever designed a centrifugal mechanism to increase dwell time as engine speed increases, kind of like like centrifugal timing advance. Or has someone already done it??

It's being done with engine management systems (CPU component drivers), the dwell changes depending on load and conditions. An individual coil per cylinder has the opportunity of a longer saturation time so it's possible to have greater spark performance. And timing can be adjusted at each individual cylinder to compensate for dwell changes.

problem in the secondary, as in LubeDudes picture, an open coil secondary tower.

I have to clarify here. The problem I'm eluding to, the "open coil secondary tower", is a problem only because a secondary cable isn't securely connected to it. Technician A still stands by his claim that the coil as pictured above is a good one.

dogsdad · Jun 4, 2005

Re: OK, Gearheads!

Aahhh...but here, skinnywater, I would ask Technician A to hook everything up and verify that the same thing does not happen when the system is in operating condition---but I concede that he could be right! As far as the on-the-fly dwell adjustments go, I was wondering if there was ever an attempt to do the same thing mechanically. I recall some stuff in Hot Rod and Car Craft magazines of old, such as the old Vari-Cam. I was just a youngster in those days, and never had the opportunity to acquire first-hand knowledge about such things. I do recall asking a knowledgable adult about the Vari-Cam, and I recall being told it was junk and a gimmick. Last comment---we're seeing a separate coil for each cylinder these days. It's kind of amusing that this was done on at least some of the old four-bangers they put in the Model T! This has been an enlightening thread. -dd-

kenimpzoom · Jul 7, 2005

Re: OK, Gearheads!

DId ya ever figure out the problem? Any pics? Ken

LubeDude · Jul 7, 2005

Re: OK, Gearheads!

Funny you should ask today of all days. This is the first time I have had to put this thing back together. Yes I replaced the coil, also the fuel pump while I was in there, new plugs,(they werent that old) and changed the oil, (Delo400 15W-40). Anyway, the problem is gone, Im sure it was the coil though. So its been a good day driving around in a 1965 Nassau blue Corvette. Had to be sure it was fixed, Right. Also wanted to get some of the old gas out of it and freshen it up. Why did we like these old turds anyway? Rough riding, uncomfortable, gas eatin, ill handling, Fast, Women gittin. Oh ya, it was the last two, now I remember!!

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OK, Gearheads!

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