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Plug Wires


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In a recent thread I do not wish to hijack, mention was made that 6v and 12v plug wires are different. Since the coil produces high voltage in the (typically) 20,000-30,000 volt range my understanding is that the primary coil is sized to use either 6 or 12v depending on the system (actually sized for less but for discussion's sake - see "ballast resistor") and the secondary coil is sized for the 20-30kv. The secondary voltage is sized to make the specified plug and gap fire, before electronic ignitions (1962) this was typically .030"-.035".

 

High Energy Ignitions may reach 40-50kv and a designed for a much larger gap but some are better than others. thirty years ago the Buick 3800 switched from a Magnavox ignition that could reliably fire a .045" gap to a Delco ignition that was good with a .060 gap. (the wider the gap that will fire, the more likely a lean mixture will ignite).

 

The plug wires need to be matched to desired plug gap which determines flash point and required high voltage. The vehicle voltage, 6 or 12, has nothing to do with this particularly with a points ignition.

 

Now aside from  a need to use quality plug wires, the real question is where to use resistive (keeps ignition noise out of the radio) or non-resistive. I prefer to use 8mm plug wires rather than 7mm mostly for lower resistance which helps out ELI the ICE man (how plugs fire).

 

Now what is probably of interest to AACA member is when did Delco Packard plug wires switch from Embossed to Silk Screened legends.

 

ps can anyone identify this fifty year old plug wire set:

 

 

 

 

 

71wire.jpg

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Joe P. Beat me to the answer -- That is the trial 1973 - 1974 Pontiac

Unitized Ignition System, indeed.

(It failed as a system, miserably..)

I had two (2) of those sets --- N.O.S. DELCO -- ONLY -- It took me 

20 years to sell those 2 sets --- But, I made two Pontiac Owners

VERY happy !!!

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Solly mobile, was available in late 71 and in the 1972 options guide. Considered ordering on my 72 Wagon but was working at Delco Remy at the time and was advised not to.

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32 minutes ago, padgett said:

Solly mobile, was available in late 71 and in the 1972 options guide. Considered ordering on my 72 Wagon but was working at Delco Remy at the time and was advised not to.

 

Correct.  From an article in Hot Rod:

 

"Introduced late in the '71 model year, the K65 Unitized distributor first received mentioned in Pontiac Technical Service Bulletin 71-I-60, dated April 21, 1971. "

 

Of course, by 1974 it was replaced by the widebody HEI distributor.

Edited by joe_padavano (see edit history)
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52 minutes ago, padgett said:

 was working at Delco Remy at the time and was advised not to.

Reminds me when I was considering putting 78 Eldo rear disc brakes on my 69 Toronado. The Olds Zone service manager said "please don't".😲

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If you guys have the catalogs that show it, I would have to "dig one up" at this point...

Since I haven't had any of those wire sets in 15 years, No need to do so...

If it was '71 - '72 , and not '73 - '74, I suppose that could be.

(Obviously, I didn't look it up, and they are gone anyway....)

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31 minutes ago, padgett said:

It is listed in the '72 Pontiac options catalog as part of a group. Bottom of the right page AFAIR. Will have to do a dig.

 

Here ya go. And you're right - bottom RH corner.

 

1972_Pontiac_Accessories-01.jpg

 

1972_Pontiac_Accessories-18-19.jpg

Edited by joe_padavano (see edit history)
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For them's what can't see, here it is. I just sorta remember it being part of a package and available on 400 4bbls. Was a late car, is that an early booklet ?

 

 

unitized.jpg

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So here is my take on the technical stuff in the original post.  Wires are not unique from 6 volt systems to 12 volt systems.  The primary winding of the coil is designed for one voltage or another, I.E. will have either a difference in wire gauge of the primary coil winding or may be adjusted by changing the number of turns of wire in the primary winding of the coil.  A good 6 volt coil could produce secondary voltages comparable to a 12 volt coil, it just used a little more primary current to do so.  Also there may be a difference in the primary winding depending on whether or not a coil resistor is installed in the primary ignition circuit.

 

Wire size is a misnomer or at least misleading because it doesn't necessarily indicate a difference in the size of the conductor, it is more likely the size of the insulation around the conductor that changes.  So the advantage of an 8mm wire over a 7mm wire is it's ability to resist external leakage or arcing.  This is definitely an advantage in high voltage capacitor discharge ignition systems, probably doesn't mean diddly squat for a 6 or 12 volt battery coil ignition system.  

 

Wire size then wouldn't necessarily affect the size of the plug gap.  What controls the maximum plug gap is the secondary voltage available at the spark plug.  Wider gaps require more voltage at the plug.  That's why before the advent of capacitor discharge systems and their higher voltage output we were confined to plug gaps of 0.025-0.035.  Along came the EPA and we first got CD ignition because it could support 0.050 plug gaps which helped with emissions by reducing misfire and plug fouling.  Later we added engine control modules which greatly reduced emissions by advancing the spark until a knock sensor told the system it was too far advanced.  Cars today under light throttle and low road load run unheard of spark advance and or curtail fuel delivery to improve emissions and mileage.  

 

Radio interference from ignition systems and other electrical equipment has been controlled or reduced in numerous ways including carbon filament plug wires, resistor plugs and adding condensers to some electrical equipment to prevent radio frequency interference.  Spark plugs in most cars today get their spark from individual coil units attached directly to the plug so there is virtually no spark plug wire to make noise.  To the extent possible other RFI noise sources are dealt with in engine control modules or other solid state circuitry that eliminates the need for external condensers on items like the voltage regulator.  In the old days I replaced carbon plug wires with solid copper core wires and just ran resistor spark plugs.  That seemed to prevent misfire due to crappy plug wires and kept most radios happy, especially the one installed in my car.

 

Cheers-

Dave

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23 hours ago, padgett said:

High Energy Ignitions may reach 40-50kv and a designed for a much larger gap but some are better than others. thirty years ago the Buick 3800 switched from a Magnavox ignition that could reliably fire a .045" gap to a Delco ignition that was good with a .060 gap. (the wider the gap that will fire, the more likely a lean mixture will ignite).

 

 

I am fairly certain that the modules are interchangeable. (It has been a long time since I worked on those engines) The Delco coils could be individually changed as there were three different coils along with the electronic module.  The Magnavox coils were a one piece coil pack and module and if one coil went bad, the complete coil pack needed to be replaced.  Early Delco coils had some issues that were quickly fixed.  The rest of the specifications were the same.

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I think it’s interesting to see so many people chime in on the ignition systems. One poster referred to the Kettering system, while others refer it to Delco. Lots of fun things at play from early trembler systems, magnetos, single-dual-and triple spark plug set ups. Also the real obscure stuff like a dual spark single plug system using both battery and magneto. Different era engines and carburetion, F heads, T Heads, L heads, OH V’s. Compression ratios, flame speed, octane, combustion chamber design, oil control rings, and modern computer and pollution controls. Remember the 80’s setting up the GM feedback carbs.........and my personal favorite........twenty vacuum lines running everywhere. Today’s coil at plug is fantastic. Hall effect sensors, variable cam timing...........and now all the new crazy automatic transmissions with more gears than you can shake a stick at. Driving some of today’s insane super cars are really mind boggling. The technology coming down the pipe is actually too much in my opinion. Half a dozen cameras or more looking at traffic control, and the bumper in front and behind you. I just helped out on a 2021 Porsche that had not been delivered to the customer yet...........both batteries went dead in a commercial car hauler. The car wouldn’t move, the doors wouldn’t open. They had to drive the truck to the dealer to hook it up to a jump pack to open the doors and hood/trunk. After a while on the charger, it started. I really enjoy rolling down my windows in my twenty year old Ford that’s the every day driver...........how much junk does a car need in it? 

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Posted (edited)

And who can forget the Sears Twingle.

 

First time I saw a dual fire ignition (like on the Buick 3800) was on a Honda Dream 150.

 

And can someone please explain why a modern car with DOHC (double overhead cams), VVT (variable valve timing), four valves per cylinder (count them - from the Radio City Music Hall), and a torque band that is 90% of peak from 1800 to 6500 needs a 10 speed tranny ?

(remember driving twelve speed boxes with over and under and needed both hands to shift (one through the steering wheel) but that was with a diesel that had about a 500 rpm torque band...)

 

ps thought I was the only one who cared about flame propagation rate and plug location. Have always liked a crossflow head. Ford "snakes" was the ultimate.

 

 

Edited by padgett (see edit history)
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