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Newbie - 1972 Valiant

Discussion in 'A Body: Duster, Valiant, Dart, etc' started by Nebraskaorville, Aug 10, 2017.

  1. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Which is almost certainly the infamous ballast resistor.

    The reason that coil is a 6V coil, is that up until the mid-1950s, cars ran a 6V positive-ground electrical system. When the switch was made to 12V negative ground, coil manufacturers wanted to supply product that would still fit legacy applications. So, enter the ballast resistor.

    When you are cranking, full battery voltage (12V) goes to the coil, to assist in prompt starting. This very short duration does not damage the coil, but continuous operation would. So engineers put a large ceramic resistor (5W or 10W) inline between the ignition and the coil for operation while the engine is running. It drops the voltage to the coil to a safe level for long life.

    These resistors, being encased in a ceramic material, are brittle and fail in time. Then the car tries to start, but stalls when you release the key, as it switches over to the circuit with the (open) resistor in it.
    Cars with electronic ignition have a dual ballast resistor, so that the voltage is dropped a small amount on cranking, and a larger amount when running.

    If you put a multimeter across the resistor on the firewall, you will likely get a reading of infinity (open). Normal reading is a few ohms.
     
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  2. Nebraskaorville

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    Thanks Bob! So, i'm running a 4-prong ignition module (new), single-pickup distributor, 12v coil (new - replaced 6v) and a two-wire ballast resistor.
    The diff between the two coils is that the 6v says "no external resistor required" and the 12v says "use external resistor".

    One of the other members posted i should replace the two-wire resistor with a 4-wire and "rewire per later wiring diagram".

    Thoughts? Simple description on rewiring for the 4-lead resistor?

    Should I replace the condenser that was attached to the + lead of the 6v coil? Do i need it at all?

    Thanks again.



    In other news, i scored a "runs good" 318 out of a junkyard "Trans Van" from the 70's. will post pics. $200 pulled and delivered to the house.
    Will begin rehab soon.

    IMG_3926.JPG
     
    #62 Nebraskaorville, Sep 27, 2017
    Last edited: Sep 27, 2017
  3. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    All the electronic ignition cars I've seen have a dual ballast resistor, 4-wire, so I'd use that. I'm not familiar with the wiring diagrams associated with it, but others here have helped with that in the past, and may be able to post them.
    I'd still use the external capacitor on the coil. I think it was there to reduce spikes from breaker points, but it can't hurt to have it.
     
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  4. 68RT

    68RT Well-Known Member

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    6 volt coil is for 6 volt systems. 12 volt coils that require a resistor, are actually a 9 volt coil. That way you have appoximently 9 volts during starting (resistor bypassed) and running (resistor in line). 6 volt coil would give a hot spark for a while but will overheat and fail from high voltage. Could cause resistor failure too.
     
  5. Nebraskaorville

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    Thanks guys, I'll replace the ballast resistor with a 4-lead unit.

    Looks like this donor van engine is a 1978 318. I'm thinking my 1972 318 heads will breathe better on it than whats on there now- provided its stock? Thoughts?
     

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  6. pt006

    pt006 Active Member

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    I'd recommend using the original dual terminals from the van for the 4 prong resistor. This eliminates confusion in the future. Without a wiring diagram it is hard to explain, but here goes. Note that wire colors change over the years.

    The connector plug terminals for pins 4 and 5 go to the base of the distributor. Pin 2 terminal goes to the negative coil stud. Pin 1 goes to ign. run and also to the dark blue wire side of the resistor. The dark blue prongs are connected together. Pin 3 goes to the 'other side' of the resistor thru the 5 ohm resistor. The ignition start wire [brown?] goes to the positive coil stud and also to the 'other side' of the 0.5 resistor.

    Ign. run may be dark blue or yellow.
    Ign. start may be brown or pink.
     
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  7. pt006

    pt006 Active Member

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    I don't think the '78 heads will flow any better. But, they have hardened valve seats.
     
  8. CudaPete

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    Box.jpeg.jpg Ballest.jpeg.jpg

    Here's my Mopar Performance conversion
     
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  9. Nebraskaorville

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    78 engine is onsite!
     

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  10. pt006

    pt006 Active Member

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    orville; nice engine stand. The 3 wheel type are tipsy.

    Pete; Nice neat wiring job.
     
  11. Nebraskaorville

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    Hey guys! Just updating -the 78 engine is on the stand and stripped to the block. I'll be doing a hone/ring job and then cleaning everything up (just gonna wire-wheel the heads, don't plan to tear them down) and reassembling. I don't plan to replace any bearings - does anyone know the torque spec for used rod bearings? Here are some pics. Thanks all!

    val1.jpg val2.jpg val3.jpg val4.jpg val5.jpg val8.jpg
     
    #71 Nebraskaorville, Oct 19, 2017
    Last edited: Oct 19, 2017
  12. Fast Eddie

    Fast Eddie Valued Member
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    Replace the valve stem seals while the heads are off......................
     
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  13. dana44

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    Yes, definitely listen to Fast Eddie. I would also get some lapping compound and dress the valve seats. Since it is apart, the stem seals and dressing the valves are going to help her last a whole lot longer than just cleaning them and leaving them alone, they look to be leaking a little oil (the valve stem seals), and dressing them will help with the compression.
     
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  14. pt006

    pt006 Active Member

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    Rod cap bolts are torqued to 45 ft lbs. Carbon builds up on the back of intake valves, so a head/valve clean up is a good thing to do. Changing the cam timing gear and chain is mandatory. I would at least plastigage the mains and check the rear main seal for leaking. I'd replace the rod bearings.
     
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  15. Nebraskaorville

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    Thanks man. I reckon i'm going elbow-deep.
     
  16. Nebraskaorville

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    Thanks Dana. The oil in those chambers was added by the yard through the sparkplug holes.
     
  17. dana44

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    Oil added to the cylinders is one thing, both valves being almost and totally black is another. The exhaust valves should be more tan colored, thus a clean-up of the valve seats is well worth the time it will take to dress them up a bit.
     
  18. Nebraskaorville

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    Hey guys - updates. Heads are at a shop for cleanup/stem seals.
    My engine stand mounting arms are showing cracks, so i'm shopping for heavy duty arms. Right now i have extra support via a come-along but am stalled until i get better arms.

    It has been recommended that since i have some pitting that i should do a good heavy hone job and install rings that are .05 over and then grind ends to make them fit if i need to. Does anyone know what the measurements on a set of .05 over rings would be?

    Thanks guys!
    cyl.jpg cyls.jpg ear.jpg pit.jpg
     
    #78 Nebraskaorville, Nov 9, 2017
    Last edited: Nov 9, 2017
  19. 68RT

    68RT Well-Known Member

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    You need to pay attention to any taper before doing that.
     
  20. Nebraskaorville

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    Been looking at bumping the cam a bit. In this description they talk about a zinc additive. Why? Metallurgical thing?
    Thanks guys!
     

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