Posted: Fri Aug 05, 2005 2:32 am Post subject: Mallory dist question
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I am running a mallory dual point dist. I was running a stock blue coil do I need to run a in line resistor or a different resistor coil to keep from burning my points,I took it out 2 days ago for a 1st time test run and I burned up the condensor..
If this has never happened to you it can be quite puzzling as to what causes the motor to run to crappy until you have had this prior experience.
Well I replaced it today and it started right up and ran fine but what can I do to keep this from happening again.
I am NOT running stock wiring so if there was a factory inline resistor wire being uesd it isnt now...
do I use a bigger output coil, a internal resistor coil, a inline ceramic resistor, or what.... Puleassssseeeee let me know so I can take it out on a run and feel safe not to break down for something this small but harder than hell to trace... Thanks,Dennis
Mallory Dist. question
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raygreenwood
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Generally VW wires have resisitors at the ends. You have to have a resistor somewhere. Its usually either a resistor coil and non-resistor wires or the other way around. Check your condensor too.
Also...get rid of those damn points and get a pertronix or acompufire module. Huge improvement over points. No adjusting...no burning. Ray
Also...get rid of those damn points and get a pertronix or acompufire module. Huge improvement over points. No adjusting...no burning. Ray
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Trike Rider
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Also...get rid of those damn points and get a pertronix or acompufire module. Huge improvement over points. No adjusting...no burning. Ray
Ray, do they make anything for a Mallory 541 dual point setup or do I have to use their big$$$ electronic setup.....
I thought the resistors at the plug ends sere for radio suspression...Besides that I dont believe they dont have anything to do with lowering the voltage to the points to keep them from burning,thats my origional question, to keep this sort of thing from happening in the 1st place,and also if it is related to the condensor going out prematurely.
I was told if I had a coil that measured 3 ohms I would not need a resistor ,if it went above that I would have to use one,anyone know about that one,I'd really like to know about this,hate to burn my stuff up....
Dennis
Ray, do they make anything for a Mallory 541 dual point setup or do I have to use their big$$$ electronic setup.....
I thought the resistors at the plug ends sere for radio suspression...Besides that I dont believe they dont have anything to do with lowering the voltage to the points to keep them from burning,thats my origional question, to keep this sort of thing from happening in the 1st place,and also if it is related to the condensor going out prematurely.
I was told if I had a coil that measured 3 ohms I would not need a resistor ,if it went above that I would have to use one,anyone know about that one,I'd really like to know about this,hate to burn my stuff up....
Dennis
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wildthings
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If you've got the stock blue Bosch coil for a Type 4 it probably does not need a resistor. At least none that I have ever owned needed one. I sounds to me like you had a defective condenser. They are far more apt to fail new straight out of the box than at any other time in their life. A bad condenser will fry a set of point very quickly.
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raygreenwood
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The resistors built into the ends of the stock leads were nit for radio suppression. It was to lend some resistance to the system to help hcarge build up. With any resistor in the system, you can fry points and condensors. There are several ways to do this. You can either have a resistor coil or resistor wires.There is also a resistor in the rotot of most stock VW. All are not necessary. But...you should find out what resistance your set-up requires from the manufacturer.
I would be willing to bet, that if you can locate a part number for your points....and then find out what other dizzys that it fits into.....pertronix probably makes a drop in points replacement for it. Ray
I would be willing to bet, that if you can locate a part number for your points....and then find out what other dizzys that it fits into.....pertronix probably makes a drop in points replacement for it. Ray
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Trike Rider
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wildthings
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Ray,
I think that he is talking about the ballast resistor that many manufactorers use in series with the ignition coil. The stock Type 4 coils do not need an external resistor, as they have sufficient internal resistance on the low voltage side. This would be true with points or an electronic pickup. However if he has changed to a coil that requires a ballast resistor he will need one or he will fry his points. The ballast resistor limits current flow through the coil and points once the magnetic field has built up in the coil so that the points don't burn as readinly and the coil does not over heat.
To the best of my knowledge resistor style plug wire or wire ends like VW uses are there at least partially for radio suppression. They do this by lowering the discharge amperage of the coil creating a longer duration spark. The total resistance on the high tension side of the coil (coil windings, rotor, wires, wire ends, and plugs) lessens the maximum initial current through the wires and across the spark plug gaps, which corresponds to the maximum current and voltage across the points as they open. The opening voltage for the points is way in excess of 12V, something like 300V. Less current and voltage means less arcing and less burning of the points. The condensor also plays a role here by momentarily shunting some of the current, again lessening the opening voltage across the points.
I think that he is talking about the ballast resistor that many manufactorers use in series with the ignition coil. The stock Type 4 coils do not need an external resistor, as they have sufficient internal resistance on the low voltage side. This would be true with points or an electronic pickup. However if he has changed to a coil that requires a ballast resistor he will need one or he will fry his points. The ballast resistor limits current flow through the coil and points once the magnetic field has built up in the coil so that the points don't burn as readinly and the coil does not over heat.
To the best of my knowledge resistor style plug wire or wire ends like VW uses are there at least partially for radio suppression. They do this by lowering the discharge amperage of the coil creating a longer duration spark. The total resistance on the high tension side of the coil (coil windings, rotor, wires, wire ends, and plugs) lessens the maximum initial current through the wires and across the spark plug gaps, which corresponds to the maximum current and voltage across the points as they open. The opening voltage for the points is way in excess of 12V, something like 300V. Less current and voltage means less arcing and less burning of the points. The condensor also plays a role here by momentarily shunting some of the current, again lessening the opening voltage across the points.
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Trike Rider
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raygreenwood
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Yep.....with a "normal" stock set-up, he should need no external ballast. But I'm wondering....might different resistance values be needed for dual points....depending on what the actual voltage is at each point opening.
I mean...does the actual current/amperage or milliamperage increase as actual voltage decreases? Or...meaning if you have twice as many points operating within a given rpm cycle rate....is the dwell time sufficent to generate two pulses of decent voltage?.
Generally VW coils are specific. If memory serves...the stock VW coil has no extra resistor built in as ...but has decent overall resistance...as wildthings noted.. It just uses a combination of the coil, wires and rotor resistance in series. Yes...it slows the current transmisson across the points.
I have seen after market coils installed that were supposed to be direct replacements...but had the wrong initial resistance...like much lower than the VW coil. They start burning points immediately.
The difference here....I'm guessing now so don't beat me up too bad.....is that the Mallory rotor may be very low or no resistance...add that with non-resistor wires....and just working from the stocki internal resistance of the blue coil...and twice the load with two points...and you may have a problem. It may be worth it to ask Mallory the specs they suggest on a dual point coil. Ray
I mean...does the actual current/amperage or milliamperage increase as actual voltage decreases? Or...meaning if you have twice as many points operating within a given rpm cycle rate....is the dwell time sufficent to generate two pulses of decent voltage?.
Generally VW coils are specific. If memory serves...the stock VW coil has no extra resistor built in as ...but has decent overall resistance...as wildthings noted.. It just uses a combination of the coil, wires and rotor resistance in series. Yes...it slows the current transmisson across the points.
I have seen after market coils installed that were supposed to be direct replacements...but had the wrong initial resistance...like much lower than the VW coil. They start burning points immediately.
The difference here....I'm guessing now so don't beat me up too bad.....is that the Mallory rotor may be very low or no resistance...add that with non-resistor wires....and just working from the stocki internal resistance of the blue coil...and twice the load with two points...and you may have a problem. It may be worth it to ask Mallory the specs they suggest on a dual point coil. Ray
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wildthings
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I have to admit here that I know almost nothing about dual points distributors. The only time that I have ever messed with any was a style that Datsun used back in the early '70s that effectively retarded the timing by powering a delayed opening set of points at certain conditions. This was Datsuns way of accomplishing what VW did with their vaccum advance/retard distributor cans.
My guess and it is just a guess is that Mallory divides the heat load from the current flow between the two sets of points. Run cooler last longer. The only problem here is that one set of points is going to still get all the arcing and subsequent pitting/build up. Maybe with cooler points you get less pitting, that sounds good at least.
My advice on running a convential point/coil system is that the condenser has to match the overal system. Assuming everything else is well matched and in A-1 condition you should get very little pitting if you have the correctly sized condenser. I seldom change a condenser especially if it is the OEM brand for the application, as I have almost never seen anything but a new condenser fail. On my own rigs I usually don't change them but once every 100,000 miles or so, and then it's because they are beginning to look bad, i.e. rust on the body or cracked insulation, not because they are not working properly.
My guess and it is just a guess is that Mallory divides the heat load from the current flow between the two sets of points. Run cooler last longer. The only problem here is that one set of points is going to still get all the arcing and subsequent pitting/build up. Maybe with cooler points you get less pitting, that sounds good at least.
My advice on running a convential point/coil system is that the condenser has to match the overal system. Assuming everything else is well matched and in A-1 condition you should get very little pitting if you have the correctly sized condenser. I seldom change a condenser especially if it is the OEM brand for the application, as I have almost never seen anything but a new condenser fail. On my own rigs I usually don't change them but once every 100,000 miles or so, and then it's because they are beginning to look bad, i.e. rust on the body or cracked insulation, not because they are not working properly.
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raygreenwood
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The most common use for dual points way back when...was having a second spark for high compression high performance engines. This is in the same vein as the MSD lost spark method. It gives two sparks in very quick succession to (a) keep the spark from blowing out at very high compressions/rpms and (b) to posssibly on some engines ignite in two places in the flamefront for better combustion. Ray