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Thread: drifting timing (I'm sorry it's VERY long winded!)

  1. #1
    Riverine elwood blues's Avatar
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    Default drifting timing (I'm sorry it's VERY long winded!)

    A little background, I have a 1978 CJ7 pretty much stock when I bought it. Okay, it was bone stock except the seats when I bought it three years ago. Last spring I started this project. I wanted to get rid of my single barrel YF carb and I didn't want to spend the money or from what I read take the time to swap in a Weber. So, I picked up a really nice Motorcraft 2100 1.08 venturi carb. I bought a used 2 barrel intake from a 1979 CJ and I bought a brand new exhaust manifold. While I had the intake and exhaust manifold off I put in a new exhaust too, new headpipe, no cat, a flowmaster 40 and a tailpipe. I also stripped anything even remotely related to the emission control stuff. So I replaced every piece of vacuum line I could find, because now it's all different.

    Did a full rebuild on the 2100, stripped it down to parade rest, replaced everything that could be replaced, power valve, accelerator pump, choke, float, needle and seat, everything. I also found smaller jets for it too. I got it all put together, had some timing issues initially, but got it all worked out and it seemed to run pretty well.

    Until, the Ford Dura-spark module crapped out, again. So, I decide that I'm not going to replace that piece of junk again. After a lot of research I buy a Summit Racing street and strip ignition control module and matching coil. New Accel non-resistor plugs and new Taylor 8.2mm 4.2L specific plug wires. Plus a remanufactured distributor, new cap and new rotor. I finally got it all together and she ran. But never ran well. I never got smooth idle or drastic change in throttle response that everyone else raved about.

    So, I picked up a different version motorcraft 2100, this one is an even older version. Again, full on rebuild, everything I can think of. Slap this new carb on, it still runs like crap, possibly a little worse.

    Last night I finally, after the CJ's sat for close to two months, got the original motorcraft 2100 swapped back on and got her fired. It's been cold here, so I had to manually adjust crank up the idle speed to keep her running for a while. It's still running like crap, so I decide to throw the timing light on it, just to see.

    As I listen to the engine idle up, then back down, shake and shimmer, darn near die, then idle back up again. I hook up the timing light, and stare down at the timing marks, in rhythm with the engine I watch the timing drifting back and forth. High idle, the timing reads 12 degrees BTDC, when it idles down and starts to shimmer and shake, I can watch the timing mark move down to probably 6 or 4 degree BTDC. Back and forth it goes, even after it's warmed up.

    I'm completely and totally confused. If anyone has a good idea, please let me know, I'm pulling my hair out. Thank you




    P.S. If it counts for anything, I have a distinctive valve-train (I'm pretty sure it's a lifter) ticking noise. Funny thing is, as you adjust the timing more or less BTDC, the ticking noise comes and goes.
    1978 CJ7 golden eagle

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  2. #2
    Senior Member HillBillE's Avatar
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    I can think of 2 things it may be.

    1. The timing chain is stretched to the max-this could also be the 'ticking' noise your hearing, as the chain will bang against the cover.

    Mine was really bad, after changing it, it timed fined.

    2. The ECU (computer) is still in the loop, adjusting the distributor.
    (not likely since you have a new ignition control mod)


    OK-scratch the ECU, it's a 78 and doesn't have one.

    I'm betting it's a worn timing set.


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  3. #3
    See Ya There!! Shadow's Avatar
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    Quote Originally Posted by HillBillE View Post
    I can think of 2 things it may be.

    1. The timing chain is stretched to the max-this could also be the 'ticking' noise your hearing, as the chain will bang against the cover.

    Mine was really bad, after changing it, it timed fined.
    I agree with HillBille.

    Okay how much experience do you have with ignition and carbs? I only ask this as a point of reference not to call you out.

    Does the distributor have vac advance?
    2003 Rubi with 6" lift rolling 37's w/ beadlocks, armor for effect. Constant state of change, its a jeep thing!!

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    Riverine elwood blues's Avatar
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    Quote Originally Posted by Shadow View Post
    I agree with HillBille.

    Okay how much experience do you have with ignition and carbs? I only ask this as a point of reference not to call you out.
    No worries, I understand. I have a good amount of experience with carbs and ignition, I'm no expert though, that's for sure. I had a 56 CJ3B when I was younger and worked as a mechanic for a couple of years before I joined the Navy, but that was more than 10 years ago


    Quote Originally Posted by Shadow View Post
    Does the distributor have vac advance?
    Yes it is a vacuum advance dist, it's nothing cool, just a remanufactured stock one I got from NAPA.
    1978 CJ7 golden eagle

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    What if I told you servicemen and women are just regular people like you. Some are douchebags, some are really great people, some are idiots, some are really smart, and almost none of themselves think of themselves as hero's, except the douchebags.

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    See Ya There!! Shadow's Avatar
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    I suspect that is the drift, as it revs up the timing will be advanced to compensate for the higher rpm's. I wouldn't worry to much at this point. Now when you stated you replace the needles, seats and jets they were a matched set (I will assume this is the case). Why did you go with a smaller size? This will restrict fuel flow and give you the symptoms you are having like lack of power and rough idle due to starvation. Do you still have the old set? Will it Idle smoothly at higher rpm's?
    2003 Rubi with 6" lift rolling 37's w/ beadlocks, armor for effect. Constant state of change, its a jeep thing!!

    SOLD - 5.9 Grand with TNT Long Arms, KM2's, HP30 w/ARB & WJ Brake Conv., Rear 44HD Trussed & Skidded, 231 w/SYE, TW Drive Shafts & Custom Sliders

    RIP: 2004 Rubi: 3" lift on 33's

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    Riverine elwood blues's Avatar
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    Not a smaller needle and seat size, just a smaller jet size. From what I've learned about the motorcraft carb swap on a 4.2L is that for it to run optimally you need the 1.08 venturi size and to be running a size 46 to 48 jet, depending on your elevation. I have a chart somewhere that references the venturi size to CFMs of the motorcraft 2100s, the 1.08 is the correct CFM for the stock 258. The jets that came in the carb when I got it where 52's, that's why I had to buy a smaller jet size.
    1978 CJ7 golden eagle

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    What if I told you servicemen and women are just regular people like you. Some are douchebags, some are really great people, some are idiots, some are really smart, and almost none of themselves think of themselves as hero's, except the douchebags.

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    See Ya There!! Shadow's Avatar
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    Here is quick trick to try. Spray some either around the base to check for any leaks. Also disconnect the vac advance line, at idle there should be no change in idle if there is then there is something wrong with the diaphragm.
    2003 Rubi with 6" lift rolling 37's w/ beadlocks, armor for effect. Constant state of change, its a jeep thing!!

    SOLD - 5.9 Grand with TNT Long Arms, KM2's, HP30 w/ARB & WJ Brake Conv., Rear 44HD Trussed & Skidded, 231 w/SYE, TW Drive Shafts & Custom Sliders

    RIP: 2004 Rubi: 3" lift on 33's

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    See Ya There!! Shadow's Avatar
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    Gad! Its been a long time since I dealt with antiques!
    2003 Rubi with 6" lift rolling 37's w/ beadlocks, armor for effect. Constant state of change, its a jeep thing!!

    SOLD - 5.9 Grand with TNT Long Arms, KM2's, HP30 w/ARB & WJ Brake Conv., Rear 44HD Trussed & Skidded, 231 w/SYE, TW Drive Shafts & Custom Sliders

    RIP: 2004 Rubi: 3" lift on 33's

  9. #9
    Riverine elwood blues's Avatar
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    Quote Originally Posted by Shadow View Post
    Here is quick trick to try. Spray some either around the base to check for any leaks. Also disconnect the vac advance line, at idle there should be no change in idle if there is then there is something wrong with the diaphragm.

    Got it, rule out a vacuum leak around the base of the carb or any of the vacuum ports in and out of the carb. Thank you
    1978 CJ7 golden eagle

    US Navy Riverines

    Jeep-CJ.com

    What if I told you servicemen and women are just regular people like you. Some are douchebags, some are really great people, some are idiots, some are really smart, and almost none of themselves think of themselves as hero's, except the douchebags.

  10. #10
    See Ya There!! Shadow's Avatar
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    Is the fuel pump new as well?
    2003 Rubi with 6" lift rolling 37's w/ beadlocks, armor for effect. Constant state of change, its a jeep thing!!

    SOLD - 5.9 Grand with TNT Long Arms, KM2's, HP30 w/ARB & WJ Brake Conv., Rear 44HD Trussed & Skidded, 231 w/SYE, TW Drive Shafts & Custom Sliders

    RIP: 2004 Rubi: 3" lift on 33's

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