Running bad & lean

Discussion in 'Big Block Cadillacs' started by pila78, Oct 11, 2018.

  1. pila78

    pila78 Well-Known Member

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    The 507 in my El Camino is barely moving the vehicle. Acts like it's starving for fuel. Checked volume & pressure to carb, removed & checked & took carb apart, carb is clean & adjustments still OK. Is it possible to have a broken valve spring (s) etc, making it lean & back-firing from the carb ?? Just an idea. Haven't pulled the valve covers to look yet...

    Bill
     
  2. El Diablo

    El Diablo Active Member

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    What do your spark plugs look like?
     
  3. pila78

    pila78 Well-Known Member

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    Haven't pulled any plugs yet. Forgot to mention that it seems to idle OK (??) As soon as it gets up in RPM, like 12-15oo, it begins to miss & fart around. I'll check the plugs tomorrow. The way it was running, I kinda suspected the IGN module, but no difference after replacing it.. Kinda doubt that the coil could be a problem... RPM a few hundred over idle seems to make it act lean, with carb back-fire etc.. It actually idles fine, so I didn't suspect a vac leak around the intake area, but may check that also..
     
  4. Darius

    Darius Well-Known Member

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    Hello Bill,

    As soon as you said, "back-fire" my thoughts went to timing issues, whether at the distributor or more likely, a jump at the timing chain.

    Darius
     
  5. Red98422

    Red98422 Active Member

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    +1. I’m with bro D on this one, i suspect something ignition related as well....hopefully not as drastic as a skipped tooth. Before you pull the plugs can you throw a timing light at it just to rule that out?
     
  6. Cad Man

    Cad Man Member

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    Not a skip
     
  7. Cad Man

    Cad Man Member

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    I highly doubt it's a skipped chain..
    Look for danged wires on or under the advance plate. Modules usually either work or don't.. maybe a bad coil.
     
  8. PJ McCoy

    PJ McCoy Active Member

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    Check your wires. They may be arcing across each other. I've seen Chebbys with old over heated wires "jump" or arc into another wire causing that cylinder to fire pretty maturity.
    Just my 2cents.
    PJ
     
  9. pila78

    pila78 Well-Known Member

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    I think I've found the problem...In the distributor, two wires on the magnetic pickup are flexing when the vac advance is moving them, and they seem to be "flexed out" !! I had those fail many years ago, and don't know why I didn't check them this time around ( must be the age thing !...I'll be 87 on Thursday !) So, today I'm gonna replace those two wires, rather than pull the distributor to change the pickup.. I'll see how it goes. I also have a new connector w/pigtails for the power & tach connector on the distributor. The lock tabs on them are broke from age....
    This engine has only around 3500 miles on it, so I don't suspect the timing set, of a jumped tooth etc.. I did pull a couple spark plugs, and they look nice & clean, so.....
     
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  10. Darius

    Darius Well-Known Member

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    Howdy Bill,

    That assessment sound logical and would be a simple fix. Hope it works!

    Happy Birthday - upcoming!! :) Just remember that we are like those magnetic pickup wires in that we've lost some of our flex!

    Best,

    bro. d
     
  11. PJ McCoy

    PJ McCoy Active Member

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    Happy birthday Bill!! A little early. hahaha
     
  12. pila78

    pila78 Well-Known Member

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    Well, thanks for the greetings !!
    I checked out the magnetic pickup, for fixing the wires etc, and saw it & remembered that is was new last year.!! A really strange thing going on here. Today, the engine runs normal, and buzzes up the 5 grand easily ! I have the new connectors/pigtail, to replace the power & tach connections, so I'll see if that helps to keep it running right !!
     
  13. pila78

    pila78 Well-Known Member

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    I replace the connector on the HEI, which combines the power & tach connections. This morning it stumbles a bit during the first couple minutes, then ran fine....weird shit goin' on here !!
     
  14. PJ McCoy

    PJ McCoy Active Member

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    As you know, it's so frustrating chasing things like this. I remember using new plug wires, 2 weeks old, having a bad miss. I chased everything but didn't do a simple inspection on my "New Plug wires"
    I found it at night back mistake. It was arcing to the block.
    Maybe fire her up at night and have a look? ID. Just taking a stable.
    Have a great one Bill.
     
  15. Red98422

    Red98422 Active Member

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    I hope you are able to get this figured out...you definitely have more patience than I, I would have thrown tools at this point
     
  16. peter dennis

    peter dennis New Member

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    When weird intermittent stuff happens with ignition, I always get to checking earths first, engine , body, distributor, etc. Once verified all good, then I start to look elsewhere.
     
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  17. pila78

    pila78 Well-Known Member

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    Since I replaced that connector, & pigtail, which I bought from Summit Racing, it has run fairly good. I do believe there are some issues with the carb yet. I haven't done any adjustments to the idle mixture screws for a year, so I may address those & see if it helps the way it runs.
     
  18. pila78

    pila78 Well-Known Member

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    Well, it still decides to run crazy at times ! Today I noticed that in neutral, it buzzes up like nothing is wrong with it at all, But as soon as it's in gear, it wants to mess with me !!:thumbdown: I kinda wondered if I may have a vacuum leak at the intake gasket area. When it quits raining here, I'm gonna do the idle speed check with my propane torch ( un-lit of course !), along the intake gasket & carb flange gasket. It doesn't idle right either, like it may be missing on one cylinder at idle. The sound in the left tailpipe has changed at idle also, so if the gasket check shows no difference, I'm gonna remove the left rocker arm/valve cover, and see if any extra parts are laying in there, like springs etc ;)
     
    Last edited: Nov 6, 2018
  19. pila78

    pila78 Well-Known Member

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    Today I did the intake gasket check, and it seems to be sealed OK. I was pulling plug wires on at a time, and the #3 (driver-side, 2nd one from front) was firing OK, but didn't seem to be affected with the drop in RPM like the others. Next I'm gone pull the left rocker cover & see if anything is visually wrong under there. Compression test may show something (?) I'll do that also.. Hope this problem will get solved, but meanwhile, I have a 350 Chevy engine & the original rear end yet, if it gets to the point that I'm just chasing my tail on this.

    I have a '74 Malibu, with a lightly built 408 SBC in it, which could pull this Caddy powered El Camino back wards, with no problem. The idea of the Cad in my Elco seems to be a bad idea, an expensive mistake it seems....
     
  20. Darius

    Darius Well-Known Member

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    Bro. Bill,

    I believe that would be cylinder number 4, if it is the second from the front on the driver's side. Or are we not talking the same lingo?

    bro. d
     

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