spark plugs black

Old Dec 1, 2010 | 08:04 PM
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1973olds98's Avatar
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spark plugs black

Pulled a few of the plugs and they were black,,Not a oily wet black but a dry sooty black...The spark plugs are ac delco r45s gapped at .40..The plugs are new only ran a few times,,,Also engine is rebuilt,,,,.Any ideas,,,
Old Dec 1, 2010 | 08:32 PM
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reading spark plugs

Heres a web site with pictures to help read spark plugs with potential trouble areas to find the source of the problem http://blog.carlist.my/wp-content/up...park_plugs.jpg
Old Dec 2, 2010 | 04:57 AM
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From the photos in that link, I'm guessing you have the situation labeled "carbon deposits," which suggests a too-rich fuel mixture which could also account for the flame you saw coming out of the headers that you mentioned in the other thread.
Old Dec 2, 2010 | 05:43 AM
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It's a 'too rich' condition - usually a carb problem, maybe an internal leak.
How does it idle?? Is the choke opening??
Is the timing set correctly??
Is the motor broken in correctly??
Has it been driven? Or just sitting and at idle?
Take it around the neighborhood and 'blow it out' if so!
I'd borrow another carb, and see if that corrects it.
Old Dec 2, 2010 | 12:02 PM
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The timing is set,,,It has not been driven,,Just setting in the garage idiling,,The choke appears to be idling...It slowly opens as the engine warms up,,,Would u guys suggest turning in the idle mixture srew 1/4 turn in..
Old Dec 2, 2010 | 12:13 PM
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too much fuel-carb problem. PERIOD!
Old Dec 2, 2010 | 12:22 PM
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Originally Posted by 1973olds98
Would u guys suggest turning in the idle mixture srew 1/4 turn in..
Why not? What have you got to lose? You could always turn it back.

But like has been said several times now, this sounds like a carb problem, and, while you've set the timing and point contacts, what about the other aspects of a complete tune-up? In other words, have you done a full tune-up? Dwell angle? RPMs at slow and fast idle?
Old Dec 2, 2010 | 01:40 PM
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Originally Posted by 1973olds98
It has not been driven,,Just setting in the garage idiling
Any American V8 that just sits and idles will have black plugs.

You don't check plug condition after idling, you drive the car, then stop and check them by the side of the road. Driving in heavy traffic for a few minutes before you check will change what you see. Idling for a long period will completely throw it off.

- Eric
Old Dec 3, 2010 | 03:33 AM
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ok thanks for your help guys,,,I do need to get it out and drive it,,But i have to put the front seat in first and fix a brake line...
Old Dec 3, 2010 | 03:34 AM
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Originally Posted by 1973olds98
But i have to put the front seat in first and fix a brake line...
Milk crate.

Parking Brake.

Sheesh.
Old Dec 3, 2010 | 03:38 AM
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lol,,,,could u explain to me how to set the idle mixture
Old Dec 3, 2010 | 06:06 AM
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should be two on the front, set them both same turn in till just seated then back out 2 turns or 1 1/2, at very low idle adjust each slo,wly to make it run smoother, less shaking side to side, reset idle lower and adjust again, now some guys turn in 1/4 turn to lean a bit. if one screw does not change idle it means a plugged jet. but listening to the engine and watch it shake is the trick. thats how i do it. good luck. also those plug color charts (when i worked on motorbikes) were meant for an engine at full throtlle then shut off and check color.
Old Dec 3, 2010 | 06:10 AM
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Originally Posted by stan 65 cutlass
also those plug color charts (when i worked on motorbikes) were meant for an engine at full throtlle then shut off and check color.
Full throttle, then shut off and instantly pull in clutch or put AT in neutral and coast to stop (you and I know it, but it's not obvious to a beginner) .

- Eric
Old Dec 3, 2010 | 07:58 AM
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Originally Posted by 1973olds98
could u explain to me how to set the idle mixture
At the risk of repeating what Stan said, to adjust the idle:
  1. Check the position of your mixture screws - they should be somewhere around 1½ to 2 turns out, but write down where they were if they're way off before you "correct" them.
  2. Make sure your timing is set right
    (Dwell angle 30°, Timing at spec. [or a few degrees advanced if it's a '71 or later], set with vacuum diconnected and plugged, with idle as specified).
  3. If you've got adjustable valves, make sure they're properly adjusted.
  4. Engine warmed up.
  5. Connect a tach and a vacuum gauge, if you've got 'em
    (vacuum gauge goes straight to manifold source).
  6. Set idle about right (as specified: in gear with parking brake on for AT cars - DON'T RUN YOURSELF OVER OR DRIVE IT THROUGH THE GARAGE DOOR - it will go easier in Reverse than in Park, so if you go from D to P without your foot on the pedal, it will go back at least a few inches).
  7. Play with each mixture screw SLOWLY. Turn in about ¼ turn, then wait to see effect, then turn again. Also try turning out. Watch vacuum gauge - the "roughness," "shaking," or idle speed drop will show a corresponding slight drop in vacuum. Set screws for highest vacuum / smoothest idle, then recheck and reset speed with speed screw, then go back to mixture screws and do it all again.
  8. After a few rounds, you'll have it perfect.
- Eric
Old Dec 4, 2010 | 04:34 AM
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awesome thanks,,I am going to go through your procedure tonite
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