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When did Resistor Spark Plugs start being made?

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My son asked me about resistor spark plugs, when were they first used?

Knowing my 58 Buick uses R45 plugs to stop interference on the Am radio I presumed that these plugs might go back to the early days of automobile radios. I know of a 1934 Ford that has a radio in it, would this date resistor plugs that far back or were they developed later on to correct the interference issue?

Inquiring minds would like to know.

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58 Buicks didn't originally come with resistor plugs. Ignition interference was suppressed by using "radio ignition wires" or  resistor wires. A condenser was used on the ignition coil  for the same purpose. The generator and voltage regulator  also had condensers. Resistor plugs came into use around 1969  or 1970 on new cars. GM was first to use them I think.

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This brings up an important point: manufacturers superceed parts constantly and the books on the parts counter reflect this. For example a 67 Pontiac 400 had a PF-23 oil filter. Look in a parts book and it calls for the PF-24. This allowed them to consolidate on one filter for both 6s and 8s.

 

Trivia: anyone know the difference ?

 

So while a 58 Buick probably came with a 45, a current book will probably show an R45 because one size fits all and it won't hurt anything.

 

Knowing things like this is part of the reason I stopped judging.

 

ps 69-70 sounds right, there are no R plugs in a 68 parts manual.

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Thanks for the replies!  :)

 

So, based on the noise suppression being reduced by wires and condensers, what was the reason for resistor plugs around 1969?

 

I believe they are a hotter plug correct (is that the right wording)? Were they used due to higher compression engines or am I mistaken there too?  :unsure:

 

Should this be moved to the technical section?

Thanks for everyones time (and patience). 

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the only reason for resistor plugs is to remove radio frequency interference other than that they are the same as regular plugs of the same heat range.

Al 

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The difference between resistor,and non resistor spark plugs? The non resistor plug has the better overall performance,because when it come to electrical current:the less resistance the better current.(the downs) being that it's a non resistor plug it cause's to arc in to other electrical components,example:using a non resistor plug in an everyday car/truck etc will cause a whine in your stereo;the whine will increase,and decrease at different rpm's.this can get quite annoying for an everyday car/truck etc used for commuting.resistor plug-(the perks) The resistor plug doesn't cause any interferance with your other electrical components;such as your stereo.Electrical charge goes where it's intended to go,which is to the combustion chamber.(the downs) as mentioned before the less resistance the better the current,being that the resistor plug has resistance it will make the current run slower;to which it will have less performance than the non resistor plug.(the conclusion) if your going to have a car/truck etc performing in such as a race,then go for the non resistor plug,but if your using a car/truck etc for everyday commuting,then go for the resistor plug. There is a higher failure rate with resistor plugs than non resistor.

Edited by helfen (see edit history)

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I suspect the increase in the number of cars with FM radios in the late 60's was a driver. Noise sensitivity is different than AM.

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I suspect the increase in the number of cars with FM radios in the late 60's was a driver. Noise sensitivity is different than AM.

I think your right about the radio's my 69 Pontiac not only came with resistor plugs but also radio suppression plug wires.

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Warning: Ramble.

FM radio got its start before war the second but was "fixed" by the FCC which soon after the war moved the whole band from the 30 MHz band to the familiar 88-108 Mhz range which obsoleted all transmitters and receivers made before that. Of course most receivers had 9-25 tubes and were rather large.

Transistors made car FM radios possible and appeared in the early sixties mainly with classical and PBS stations.

Mid-60s saw FM-stereo but the problem was that when driving they would constantly switch from stereo to mono and back. So a light was constantly going back and forth with a loud CLICK sounding on each tansition. Not good.

In the late 60s two things happened:

1) Rock FM stations appeared (WMUM "Mother Radio" in south Florida was one of the first). That is where I first heard the "Legend of the U.S.S. Titanic" and "497 1/2 feet of rope" passed into legend.

2) Aftermarket FM-Stereo radios (often with 8 track) proliferated (Factory radios were Not Cheap this led to some interesting court cases, the rise of SEMA, and the "Radio accomodation package" - whole 'nother story.)

And so the need for better electronic noise contol was needed which gave birth to resistor plugs.

It helps to have been there.

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Resistor plugs sure did have a higher failure rate. They would often develop a misfire but it wasn't always the plug itself. Weak or too high resistance plug wires or other ignition problems would cause problems for resistor plugs that wouldn't bother regular plugs.

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Which bring us up to modern distributerless systems and the difference between Magnavox (fires a .045 gap) and Delco (.060) coils & 8mm wires.

However back in the Day I was running a hot Delcotronic ignition with a red coil on a late Rochester FI with what is probably one of the rarest SBC distributers known, the 1111064 for FI and Mag Pulse ignition. Used to have a spare everything for SCCA racing. Now just have some speaker stands.

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I learned all about resistor plugs when I had my then,  two year old 1973 Camaro tuned up by a patient of my fathers' who was a Buick mechanic.  He put in non resistor plugs and all of a sudden I got static on the radio.  I didn't know anything about them.  Our neighbor was a mechanic so I asked him and he showed me the different plugs and how to put them in.  Nobody but myself ever touched my car again.  I learned to do everything  from brakes on up.. It came with resistor plugs and wires. There is a happy ending to the story. Before I knew what was causing the problem,  I took out the factory AM/FM radio and put in a "cool" Audiovox  AM/FM STEREO in the dash with a Craig cassette in the glovebox.  Two 6x9 Jensen's coaxial in the rear with two round ones at the front of the console.   Every time "Get Down Tonight" came on the radio the volume would blast.   I still have the original radio in my garage.  The car is long gone.  

Edited by bubba (see edit history)

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I learned all about resistor plugs when I had my then,  two year old 1973 Camaro tuned up by a patient of my fathers' who was a Buick mechanic.  He put in non resistor plugs and all of a sudden I got static on the radio.  I didn't know anything about them.  Our neighbor was a mechanic so I asked him and he showed me the different plugs and how to put them in.  Nobody but myself ever touched my car again.  I learned to to everything  from brakes on up..  There is a happy ending to the story. Before I knew what was causing the problem,  I took out the factory AM/FM radio and put in a "cool" Audiovox  AM/FM STEREO in the dash with a Craig cassette in the glovebox.  Two 6x9 Jensen's coaxial in the rear with two round ones at the front of the console.   Every time "Get Down Tonight" came on the radio the volume would blast.   I still have the original radio in my garage.  The car is long gone.

KC's Get Down Tonight.....Why you must be a child

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GM introduced their new windshield antenna for 1970. Those radios needed all the help they could get to have decent reception.  The resistor plugs probably helped.

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Err would you believe late 1968 (1969 Grand Prix). I had a '70 4-speed (called Asphyxiation) with an Am-FM-Stereo (had a little red light when stereo was being received). I don't recall any problem with reception

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GM introduced their new windshield antenna for 1970. Those radios needed all the help they could get to have decent reception.  The resistor plugs probably helped.

 

I grew up in Seattle where one can really appreciate a good pair of windshield wipers. I remember when the GM windshield antennas came out, every time the wipers swept over the antenna, the radio would fade just slightly. It was pretty annoying but eventually you just got used to it.

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This brings up an important point: manufacturers superceed parts constantly and the books on the parts counter reflect this. For example a 67 Pontiac 400 had a PF-23 oil filter. Look in a parts book and it calls for the PF-24. This allowed them to consolidate on one filter for both 6s and 8s.

 

Trivia: anyone know the difference ?

 

. I'm going to guess that the PF-23 lacked the anti drain back feature of the PF-24, however both would fit, or there was a slight difference in length.

Does anyone remember the two piece stamped metal shield that covered the points and condenser on late sixties GM's? I think these came about as an additional static guard for the windshield antenna, and were usually discarded at the first tune-up.

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The two piece metal shield started in 1970 and was only used in GM vehicles with a windshield antenna. They were a pain to work with. Around 1973 or so Delco introduced the "Uniset" This was a points and condenser all in one.  New GM cars with the Uniset came without the shield. They didn't need it. You could retrofit the Uniset to an older model and discard the shield. And everything was fine. After 1974 there were no more points.  GM eventually discontinued the windshield antenna.

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And dont forget the allen on a flexible shaft to adjust Delco points while running.

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And dont forget the allen on a flexible shaft to adjust Delco points while running.

And the door on the cap to get you there.

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Here is what the inside of a resistor spark plug looks like,

 

The dark area in the center of the white insulator which is between the electrode and the top which is called the screw is the resistor material.

 

If the spark plug was not a resistor plug, the material would be a metal powder and look like the screw & electrode after the insulator was heated and the parts fused together.

post-87831-0-62602900-1449232002_thumb.j

Edited by Larry Schramm (see edit history)

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