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Thread: Changing dist Cap & Rotor: Modern Vortec 4.3L

  1. #1
    4.3L moderator
    Join Date
    Oct 2007
    Prescott, Az

    Changing dist Cap & Rotor: Modern Vortec 4.3L

    Hello everyone,

    I just changed my Cap & Rotor. Took a few pics and figured I'd write a little how to. I know, I know, most of you can do this with your eyes closed. But there are people who search these forums looking for general DIY maintainence how to. And if even the presence of this thread reminds you you haven't changed yours in a while, I've done my good deed for the day.

    If you don't already have a Tool Bit & Handle set, I strongly suggest picking one up. They are cheap (I think I paid $6.00) and come in handy more often than not. They even have Clutch Head bits! Clutch heads haven't been used in automobiles for 60 years! The kit also has tamper proof torqs bits, and if you work on cars you will need one at some point in time.

    a kit like this is overkill for this job, all you really need is a torqs T20, T10 & philips head screwdriver.

    Start by removing all of the ignition wires from the cap, including the ignition coil. In some applications you might want to remove and replace only one lead at a time (especially older points & HEI GM V8's & mopar dual plug V8's) but for the Vortec 4.3L everything is easily seen and marked. So I went ahead and pulled all the wires. (plus I keep the wires in their loom in order)

    For ignition wires that have been on for a while, you might want to give the boots a twist first before pulling. It's less likely to break a ignition wire if you twist them first. The same applys to the spark plug side. They can still break, and probably will. So have a new wire set available. It's probably a good idea to replace the ignition wires the same time you replace a cap & rotor. If you decide (or have to) change ignition wires too, only replace one cylinder at a time. Pull the lead off of one cylinder, match it to the new (length & boots), install the new lead before moving to the next cylinder.

    Holding down the distributor cap to the distributor is a T20 headed screw. There are two screws holding the cap down, exactly 180 degrees apart from each other. Remember, counterclockwise to remove the screws. Clockwise to tighten.

    With the distributor cap removed you will be able to see the Rotor. It too has two torqs screws holding it down, but these have T10 heads on them (some aftermarket rotors come with Philips head screws) Note the direction the rotor is pointing.

    With everything removed you are now ready to replace with new parts.
    Here you can see my old cap & rotor next to the new. I opted for a performance set that uses brass terminals instead of tin.(Summit # SUM-G5222) This is optional and not neccisary.

    When you set the new Rotor in place, you'll notice two small indexing tabs cast into the underside of the rotor. Those two tabs, one on each side 180 degrees away from each other, will sit in a hole in the hub on the distributor shaft... It is possible for the rotor to sit on it's hub 180 off, but it will not bolt down. The indexing tabs & mounting holes are spaced so it can not be installed incorrectly. Bolt down the ignition rotor, but not to tight. Just enough to seat the rotor so there is no play and you can't wobble it by hand.

    Install the distributor cap, usually the Vortec engines have the coil terminal on the backside pointing towards the passenger side. If not just be sure the cylinder numbers cast into the top of the distributor cap match the correct bank of cylinders. 1,3,5 on the drivers side. 2,4,6 on the passengers.

    like my mad Paint skills

    Bolt the cap down using the new supplied hold down screws. The new ones usually have a small amount of thread locker already applied. Again, not too tight. The distributor base metal is brittle and a base mounting ear can be snapped in half with to much torque.

    While attatching the ignition wires. I started on bank 2, Cylinders 2,4,6. Because it's open and easy to get to. Find the ignition wire down by the spark plug at the engine and trail it all the way up to the other end by the distributor. It's a good idea to use a little dielectric grease on the ignition wire terminal. Slide that ignition wires boot onto the distributor terminal that has the correct cylinder number cast into it. be sure to push it on all the way, you should feel it click into place. Be aware, on bank 1 there is an oddball cylinder location in the cap. Cyl 1 is in the center, 3 in front, 5 in back.

    And you're done. Don't you love my hideously clashing blue cap & red wires

    I only had 17,XXX miles on the previous cap & rotor. And although I didn't notice a performance increase (because nothing was severely worn on the old set) my truck uses less cranking to start now.

    Cheers ~Mykk
    Last edited by 04SilveradoMykk; 11-01-2007 at 10:39 AM.

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  3. #2
    Full Throttle Extreme! Grimm's Avatar
    Join Date
    Dec 2004
    Holy shit, dude. Very awesome writeup!
    99 Firebird - ls1 swapped
    00 s-10 - 4.3 waiting to explode
    96 f150 - 4.9 already asploded

  4. #3
    4.3L moderator
    Join Date
    Oct 2007
    Prescott, Az
    P.S. Just prior to the ignition tune up I had some fun with a bottle of SeaFoam. If you haven't done this yet, do it. Pull the intake tube (the engine will run without the MAF) and pour directly down the throttle body. Here's the vid:

    After doing this change the plugs, and clear the codes with a OBDII scanner. The excessively rich conditions plus the burning of carbon deposits & crap can and will foul out plugs. The computer will spit out all kinds of O2 codes & MAF codes.

    Check out how spotless this TB & intake are after 60,xxx miles & a seafoam treatment. We all know how well K&N's filter the small stuff. It was black in there before hand

    Cheers ~Mykk
    Last edited by 04SilveradoMykk; 11-01-2007 at 11:15 AM.

  5. #4
    Newbie mjbell1's Avatar
    Join Date
    Dec 2007
    Framingham, Mass.

    Tight Fit

    Don't forget to mention you need the hands of a small person
    to accomplish these tasks. Especially with the crab cap, things
    are way tight. My solution is to have the young lady at our local
    Custom Exhaust Shop do it for me. To get at it she sits on the
    radiator with legs on front crossmember in between radiator and
    engine. Works like a charm.

    Note: if you have an older truck, there is a AC hose running over
    the distributor. If its not covered with foam tube insulation do so.
    GM found that the cold AC line would develop condensation and
    drip it right onto your distributor.

    Good Luck



    "Blacky" 2005 Chevrolet Silverado Extended Cab V6 4.3L
    MSD 6A Ignition, Coil, Cap/Rotor, 8.5mm Wires, K&N FIPK
    Cold Air Package, Magnaflow Cat-Back Dual Exhausts, CFM
    Tech. Bored/Ported/Polished Throttle Body,
    Thermostat 180 Degree, Fuel Pressure Guage

  6. #5
    Excellent Post!....Was trying to beat night fall and was worried I might have reversed the rotor. Good to know it cannot be installed backwards. Now, if I could just get the no start issue resolved on this 4.3!

  7. #6

    4.3 No start Issue

    High mileage Vortec. Replaced poppet style injection with new spider kit. Had occasional hesitation/misfire but ran fine. New spark plugs, cap and rotor. Had ignition module tested until hot to touch. Ran test cycle like 10 or 12 times without a faliure. Would cut out more if raining. New fuel pump. new fuel filter. Plenty of pressure at motor (62 psi). New ignition coil. Changed Crankshaft sensor. Cranks quickly, will not start. THought about fuel delivery, used starting fluid, didn't work. Didnt even try. CHecked spark at plugs. Bright white/bluish. I have fuel. I have fire. Will not even try to start. Disconnected battery turned on key let sit for 5 minutes to clear any codes. Cycle key on and fuel pump can hear it pressure up and kinda wine down like pressure is built. Cranks fast but will not kick off. Are there any more components of ignition that I am not thinking about? I understand that the cam position sensor controls the injectors. Even if it failed, that would maybe stop fuel right? If it failed then I would still get a short start on starting fluid then wouldn't I? Any suggestions?

  8. #7
    tyvm for the precise way of fixing my issue. it is highly detailed and perfect for those who really need the step by step process u have written out so well!!!!

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