Mystery Engine Diagnosis

Discussion in 'Jeeps with the Buick Heartbeat' started by theroundbug, Dec 3, 2020.

  1. Trond-Jarle Pedersen

    Trond-Jarle Pedersen Active Member

    One way to check for timing chain slop is to:

    Turn the engine clockwise for half a turn to take up all slopPut a pencil mark on the balancer at 0 degrees on the timing indicator.
    Remove the distributor cap and turn the engine counter clockwise until the rotor moved.
    The number of degrees your crankshaft moved is your timing slop.

    Less is always better but as far as I know a good number is less than 8 degrees.
    (I had 12, and erratic timing when I increased rpm)
    theroundbug likes this.
  2. theroundbug

    theroundbug Well-Known Member

    Thanks for examining the situation!

    A bit of an update, I picked up the car from the mechanic after he had said it was still backfiring and running poorly. Turns out he wasn't letting it warm up enough. Because of the new aluminum intake with no exhaust crossover it's a pretty cold-blooded motor and needs a solid couple minutes of warmup before smooth operation. Having an oversized radiator and lower temp thermostat contributes to this.

    Anyway, swapping the timing set with a TA performance kit and a new timing cover seems to have fixed the problem. So to the rescue! You guys were right! Crazy how an old timing set can have such an effect. I've tested multiple times going up a long, steep hill on a highway and it had no problems climbing at 70mph with traffic. It also improved my 0-60 time by about 8 seconds. No misfires, no backfires, no shakes. It's incredibly smooth for an odd-fire engine.

    The next step will be to work my way back down the jet sizes to find the right amount of fuel. I think I can lean it out a bit, though my fuel economy has improved enormously as it is.

    Thanks to all who looked into my problem.
    Max Damage likes this.
  3. theroundbug

    theroundbug Well-Known Member

    That's a good question. When I look under the front I only see one link. It does have a stabilizer bar, I'm just not sure which component it is. It resists rolling surprisingly well on curvy roads.
    IMG_0194.JPG IMG_0195.JPG

    It's a stock exhaust with no cat, big muffler. I'd like to install headers but am concerned with fitment since available commercial headers were designed with Jeep in mind. I'm just worried about getting into a money pit making them fit and having new pipes welded.

    As far as that video you saw, that was the way I got it, everything stock. I've since upgraded/replaced most of the pieces visible in that video (mostly trying to diagnose the problem in this thread) and cleaned up the engine bay/de-rusted a lot of parts.
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    You don't have a sway bar, it's missing. The pictures are your idler arm, and Pitman arm. I can see the sway bar bushing mount holes in the frame in your first picture.

    Last edited: Feb 4, 2021
  5. theroundbug

    theroundbug Well-Known Member

  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  7. No Lift

    No Lift Platinum Level Contributor

    That is what I suspected. It probably doesn't have one because the factory never installed one. I was told I was mistaken when I said my '76 Special w/V6 didn't come with one. Even the holes where it would have been mounted in the frame were untapped. The Special was a cheaper version of the Century and with the lighter weight of the V6 compared to a V8 the factory probably decided to help keep the price down and knock off a few pounds. I also found that the front springs are very robust considering it is a V6 so I think that helped the car handle better because of their high rating.

    The sway bar you've indicated is a nice one and it will definitely help the handling, especially compared to no bar, so it is well worth it. However, I've said before that a car doesn't need a swaybar to drive correctly and in your and my car's cases the factory deemed it unnecessary.
  8. theroundbug

    theroundbug Well-Known Member

    Thanks! Yeah it has a little body roll to it, gives it that 70's boaty feel but it's sportier than expected on curvy roads. I imagine it will start feeling pretty modern with the sway bar. Ordered it earlier today.

    Maybe it just feels tight since I'm coming from a lifted cherokee with sway bars deleted. 30* roll on a minor turn was easy to achieve lol
  9. philbquick

    philbquick Founders Club Member

    Sounds like you solved your engine problem. One thing that wasn't mentioned is distributer installation. On an odd fire engine, the point cam (or HEI trigger) is NOT symmetrical. The distributor must be installed the way the book says otherwise either 3 cylinders will fire early or 3 cylinders will fire late (by 15 degrees). Maybe the timing chain solved the problem or maybe the distributor was in wrong and your mechanic put it in right when he did the chain. i.e.: if your distributor is installed a few teeth off you can't just move the wires around to make it work. Also, you can't use an even fire distributor in an odd fire engine because 3 cylinders will fire at the wrong time. Just thought I'd point that out for future reference.
    Max Damage and No Lift like this.
  10. No Lift

    No Lift Platinum Level Contributor

  11. theroundbug

    theroundbug Well-Known Member

    Yes very good points for anyone that may come across this thread in the future. That was one of the first things I checked when it first started happening, as it's one of the cheapest fixes. Free! It wasn't the issue in my case, however.
  12. theroundbug

    theroundbug Well-Known Member

    So I have the sway bar kit from summit. It did not include any hardware for mounting to the frame. Now that I’m under here there doesn’t appear to be any way to even access the other side of those holes. Any advice? It looks literally impossible to install without taking apart the frame itself.

    image.jpg image.jpg
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The factory holes are either tapped, or a self threading bolt is used. Another option is a riv nut.

    Last edited: Feb 6, 2021
  14. theroundbug

    theroundbug Well-Known Member have I not heard about this magnificent invention. What a life saver!

    Called a bunch of hardware stores, they didn't even know what they were
  15. No Lift

    No Lift Platinum Level Contributor

  16. theroundbug

    theroundbug Well-Known Member

    Thanks. I ordered both types of fastener from Amazon, I'll update which one works best hopefully by tomorrow. This seems to be a rarely talked about, but common situation. Glad this thread documents the process :)

    There is only about 1/4" of material for threads to be cut into. Seems suspect to me considering the amount of weight these bolts are going to be supporting, but we'll see.
  17. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yeah, you would think so, but the factory used those self tapping bolts and it was good enough. I have a 1 3/8" bar up front with poly bushings and end links and I have never had a problem with the bolts loosening or pulling out. The bar works by resisting twisting, so the bushings are there for the bar to rotate inside of. Apparently, there isn't that much force there to contain.
  18. theroundbug

    theroundbug Well-Known Member

    So 5/16 self threading bolts were too small, in fact the diameter of the holes were nearly exactly the outside edge of the threads. The rivet nuts were too large unless I use the second smallest size, which was considerably loose in the hole. Frustrating.

    I ordered 3/8 self tapping bolts, hopefully they aren't too big. The other option I found was these, maybe they would work.
  19. No Lift

    No Lift Platinum Level Contributor

    Interesting find there. Well, a 5/16" hole is what you would drill for a 3/8" bolt to tap so they should work. I'm wondering if they were going metric already with the hole size?

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