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Thread: Spark plug wires 7mm or 8mm

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    Darth Vader AUSMHLY's Avatar
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    Spark plug wires 7mm or 8mm

    1964 3000 MkIII, BJ8

    I'm using a Pertronix ignitor, Pertronix top entry brass distributor cap, (Moss) premium Ignition rotor (red), Lucas Sports coil and Champion RN12YC spark plugs.

    What brand and mm spark plug wires are people using or recommended for this set up?

    What timing degree would be recommended?

    Thank you.
    1964 BJ8 phase II

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    Yoda
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    Re: Spark plug wires 7mm or 8mm

    The stock, stranded copper wires are, I believe, 7mm but most modern suppression wires are 8mm IIRC. I'm guessing a modern cap will use 8mm.

    I'd stick with the recommended 15deg BTDC@ 600RPM with the advance disconnected and plugged, or 35deg total at over 3K RPM (if you have an advance meter).

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    Darth Vader AUSMHLY's Avatar
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    Re: Spark plug wires 7mm or 8mm

    The Pertronix top entry brass distributor cap I have I'm using 7mm Pertronix wires. I believe it will take 7mm or 8mm?
    I was using copper wire but it affected the tach. With
    Pertronix wires, tach works properly.
    I question if I should use 8mm wires being I have the Lucas Sports coil and Pertronix ignitor.
    1964 BJ8 phase II

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    Yoda
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    Re: Spark plug wires 7mm or 8mm

    Call Pertronix; in the past, at least, they have been helpful. Note Pertronix specifies an impedance min/max, so you might want to verify a Lucas Sports Coil meets their specs (I suspect you won't be the first person to ask).

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    Darth Vader AUSMHLY's Avatar
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    Re: Spark plug wires 7mm or 8mm

    Will do. Read posts where Lucas coil and Pertronix ignitor are used. Haven't read about which spark plug wires in mm or brand.
    1964 BJ8 phase II

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    Yoda steveg's Avatar
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    Re: Spark plug wires 7mm or 8mm

    I'm using Pertronix 7mm Stealth wires with my top-entry 22D distributor & Pertronix II ignitor. They make these plain black sets for those who want a period look without the bling. I gave up on the straight boots as I kept pulling the wires out of the terminals.

    IMO the Lucas sports coil is fine with the Pertronix. Pertonix doesn't recommend copper wires anymore, although everyone says they work fine with Pertronix I but not with advance timing lights.

    Some British racers had Pertronix failures due to imperfect grounds through the various joints in the distributors. I ran a separate ground wire from the Pertronix mounting plate to the chassis at the coil mount. Belt-and-suspenders.

    screenshot.1881.jpg
    Steve Gerow
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    Maker of most complete Big Healey rear disc kit
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    Re: Spark plug wires 7mm or 8mm

    I've beening using Accels 8MM on my racer for year, https://www.summitracing.com/parts/acc-4041/overview/ Mated with the Pertronix Ignitor II it has worked well under race conditions for many seasons.

    Ruddspeed Race Motor.jpg
    Attached Images Attached Images
    Dougie
    '65 BJ8 3000 MKIII GN.29
    '57 100-SIX MM Vintage Racer GN.1 #414
    Team Healey PDX

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    Yoda steveg's Avatar
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    Re: Spark plug wires 7mm or 8mm

    Dougie - what is the black pipe going rearward from the upper radiator hose?
    Steve Gerow
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    Maker of most complete Big Healey rear disc kit
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    Luke Skywalker dougie's Avatar
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    Re: Spark plug wires 7mm or 8mm

    Quote Originally Posted by steveg View Post
    Dougie - what is the black pipe going rearward from the upper radiator hose?
    I thought you would pick-up on this quicker, here's my responces to Linwood's PM right after my post.

    HAHA.....I wondered how long it would take and who would respond on this. So what we've found through many race hours and dyno testing, the rear cylinders don't get
    enough cooling/water flow and always runs much hotter then the rest. (back to the poor head design) Solutions is to increse flow.
    Dougie
    '65 BJ8 3000 MKIII GN.29
    '57 100-SIX MM Vintage Racer GN.1 #414
    Team Healey PDX

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    Re: Spark plug wires 7mm or 8mm

    Quote Originally Posted by dougie View Post
    I thought you would pick-up on this quicker, here's my responces to Linwood's PM right after my post.

    HAHA.....I wondered how long it would take and who would respond on this. So what we've found through many race hours and dyno testing, the rear cylinders don't get
    enough cooling/water flow and always runs much hotter then the rest. (back to the poor head design) Solutions is to increse flow.
    Thank you for the answer. Very interesting. Could do without the snark, though.
    Steve Gerow
    Altadena, CA, USA
    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow


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    Darth Vader AUSMHLY's Avatar
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    Re: Spark plug wires 7mm or 8mm

    When is it time to replace spark plug wires?

    How do you determine if they are good? I've tested them with an ohm meter and get different reading depending on length. I'll assume if it getting a good reading, the wire is good?
    Do they eventually start wearing out and it's just a good idea to replace them?

    Some shops install new everything when they do a tune up. Points, cap, wires, plugs.

    As a side question, what about the Pertronix Ignitor replacement. It's good until it's not working, or to be safe, replace after x yrs or miles?
    1964 BJ8 phase II

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    Yoda John Turney's Avatar
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    Re: Spark plug wires 7mm or 8mm

    What goes bad on the wires is the insulation. If you run the car at night in a dark garage (with the door open) and see sparking, it's time to replace. If you touch the wires when the engine is running and you get "bit", it's time to replace.
    John, BN4

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    Great Pumpkin Keoke's Avatar
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    Re: Spark plug wires 7mm or 8mm

    Quote Originally Posted by John Turney View Post
    What goes bad on the wires is the insulation. If you run the car at night in a dark garage (with the door open) and see sparking, it's time to replace. If you touch the wires when the engine is running and you get "bit", it's time to replace.
    YEP , However since we are alking about new wire the one that fits the hole in the diszzy cap is the one to use. Stranded copper wire works good for me
    combined with resister plugs.
    1966 Daimler V8 Saloon; Safely Fast, Built to Last & and; Smooth as Glass.
    1966 BJ8 [ 2 ] Lil Red & Miss bLU
    1985 XJ6 Saloon
    1948 & 70 Lincoln continentals
    1973 Volvo P1800ES

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    Re: Spark plug wires 7mm or 8mm

    Open bonnet in the dark, fire up engine, see sparks, replace wires. Easiest way.
    Larry K
    58 Jag 3.4 MK 1 auto under restoration, 57 Jag 3.4 MK1 manual (parts car),
    03 Cooper S, 2011 Cooper S Countryman, 2011 Land Rover LR4 HSE LUX, 1964 Valiant V200
    Also had , 68 Cortina 1600E, 64 Spit 4 & 80 1500, 73 GT6 3, 71 XJ6, 79 XJ6, 86 XJS V-12, 53 XK120 OTS.

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    Yoda
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    Re: Spark plug wires 7mm or 8mm

    Quote Originally Posted by AUSMHLY View Post
    ... As a side question, what about the Pertronix Ignitor replacement. It's good until it's not working, or to be safe, replace after x yrs or miles?
    Theoretically, they should last forever. A few years ago I replaced the one in my BJ8--I wanted to carry a spare, ready to go, so I installed the new one and put the old one in the boot--but it wasn't a drop-in as they've changed the baseplate and the car needed to be re-timed. I'd put probably over 75K miles on the old one, and it was running fine.

    I had an old '79 Subaru, and it had a module that looked just like a Pertronix, and it was going strong at 175K miles.

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    Re: Spark plug wires 7mm or 8mm

    When asking a shop for a tune up, why do they replace everything. Cap, rotor, points, wires and spark plugs.
    Don't they check the wires to find out if they need to be replaced?

    Replacing / selling wires makes a profit?
    Labor to check each wire is more then the cost of a set of replacement wires?
    Don't take any chances, replace the wires?
    Gives guys like us something to discus?
    1964 BJ8 phase II

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    Obi Wan LarryK's Avatar
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    Re: Spark plug wires 7mm or 8mm

    I learned when I first started started working on cars, my Dad worked for a shop and would reccomend full cap, rotor wires, etc every couple years, was a given back in the 50s. Then, I worked in a shop and an older Master Mechanic (not technician, they weren't around yet) asked me what a tune up was. Explained the proceedure my Dad taught me and he said "No!" "A tune up is the fixing of a running problem!" " If you replace everything you hide the problem and it will come back!" "Fix the problem, then do the maintenance!" Back then, you would take the time to check each wire with an ohmeter and disassemble carbs starters and generators. Hourly wages and shop charges prevent that today as (technicians) can't do it.
    Larry K
    58 Jag 3.4 MK 1 auto under restoration, 57 Jag 3.4 MK1 manual (parts car),
    03 Cooper S, 2011 Cooper S Countryman, 2011 Land Rover LR4 HSE LUX, 1964 Valiant V200
    Also had , 68 Cortina 1600E, 64 Spit 4 & 80 1500, 73 GT6 3, 71 XJ6, 79 XJ6, 86 XJS V-12, 53 XK120 OTS.

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    Re: Spark plug wires 7mm or 8mm

    Quote Originally Posted by AUSMHLY View Post
    When is it time to replace spark plug wires?

    How do you determine if they are good? I've tested them with an ohm meter and get different reading depending on length. I'll assume if it getting a good reading, the wire is good?
    Do they eventually start wearing out and it's just a good idea to replace them

    Some shops install new everything when they do a tune up. Points, cap, wires, plugs.

    As a side question, what about the Pertronix Ignitor replacement. It's good until it's not working, or to be safe, replace after x yrs or miles?
    Just carry a spare dizzy in the boot
    1966 Daimler V8 Saloon; Safely Fast, Built to Last & and; Smooth as Glass.
    1966 BJ8 [ 2 ] Lil Red & Miss bLU
    1985 XJ6 Saloon
    1948 & 70 Lincoln continentals
    1973 Volvo P1800ES

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    Yoda steveg's Avatar
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    Re: Spark plug wires 7mm or 8mm

    Quote Originally Posted by Keoke View Post
    Just carry a spare dizzy in the boot
    Agree.

    Because I run a Pertronix II, my spare dizzy, cap and wires are set up with a Distributor Doctor condenser and points in the hope that if something fries my Pertronix, the same issue won't fry my condenser and points.
    Steve Gerow
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    Maker of most complete Big Healey rear disc kit
    Check out my galleries:
    http://www.pbase.com/stevegerow


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    Yoda
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    Re: Spark plug wires 7mm or 8mm

    All this talk about frying to me to thinking about what could fry a Pertronix (and breakfast). It's well known a Pertronix 'I'--they were never called that AFAIK--can be cooked if you leave the key in the 'run' position with the engine off for more than a few minutes (but the II, I believe, has protection for this). All they do is switch 12V to the coil so, but if your voltage regulator went bonkers and put very high voltage into your system it could kill one, but this isn't likely (I did have a VR fail and overcharge my battery, but the Pertronix survived). If your coil developed a dead short on the primary circuit your engine wouldn't run, of course, but if you left the key on 'run' you'd kill your Pertronix in short order. Otherwise, I've not heard of a lot of them failing, and when they do it's all or nothing. I've got Pertronix Ignitors on 4 cars and none of them have ever failed (granted, 3 of them haven't been driven a lot of miles). However, I've been hearing about quite a few condenser failures in recent years.

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