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Spark plugs black

3171 Views 114 Replies 9 Participants Last post by  ericnova72
Hello all,
Can you take a look at these plugs and tell me what’s going on? I just installed them and have only idled this freshly rebuilt and already broken in cammed 383 stroker. The strap is shinny black. The center electrode is flat black. These are brand new Autolutes 3924. I was fighting a very rich stinky idle with this AED Holley 750 DP, but fixed it and trashed the old fouled plugs. I’m running MSD 6A and a lot of timing at idle. 36 degrees.
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Wet/Shiny is poor oil control. Gas is usually dry powder.
Plug is too cold, add 2 degrees and a better brand of plug....in my opinion.

Gauging a plug on idle time only is nearly fruitless.
 

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I’m still running breakin oil. I will drive it around. These are autolite 3924. I was thinking of switching to NGK. Where could the oil be coming from? The engine was just built by a reputable builder.
Rings, valve guides, intake manifold are most likely suspects.
A leakdown will give you a good idea on ring conditions. When the holes prepped right, the rings should have seated by the time you were done with the valve lash.
You may have to to put a good load on the engine for a little bit in order to get them wearing in well.
 

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Joe knows his stuff.....but this is WAY out of context.
DO NOT TUNE the hesitation out of it with the IAB's and IFR's. That's the wrong way of doing it.
AED makes good carbs, at least the ones Ive seen work well but the holes in the throttle plates is a good sign the carb was messed with after is left AED. If AED sent it that way, well then, .......I'd be looking elsewhere.
 

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Your builder is mistaken. He's blowing smoke up your as. Stop asking him questions.
Verify TDC with a piston stop and the damper.

Set timing. 36 if fine for now.
I'd expect 20 initial, all at 3100, 34-36 total.

Try this.

1. Set primary to 0 idle rpms
2. Set secondary to 800-1000 rpms
3. Set primary for additional 400, total rpm should be
at 1400 rpms
4. Blip throttle to 2100-2500
(NO MORE)
Wait 3 seconds the. Blip again to 2100-2500
5. On the second blip the rpm should drop to
1400rpm... exactly!
6. If under 1400 rpm turn idle mixture screws in 1/8,
7. If over 1400 rpm turn idle rixture out 1/8
8. Set this process twice.then start over at #1.
9. Do complete process 2-3 times.
10. Close both front a rear evenly, so the rear is doing about 60 percent of the idle control.

If that doesn't help than I suspect late cam timing.
 

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Very possible. Pull it out of the cover and leave it out for now.
Have a leak down tester?
Another easy to do test is lower the floats WAY WAY down and see wha happens. If it's better, it's a indicator of the idle feed circuits. With the levels really low in the bowls, it's much harder for the passing air to pull from any of the main circuits.
Another thing you can do is close off the front or back holes entirely. Shut off the fuel and closed the blades so the carb basically becomes a 2 barral and see what happens. Trying do the same withe other side and note any differences. This process of elimination is free other than time and might lead you to the problems.
 

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Ball park anyway.
Usually I see them in the 70-30 range but that makes it richer....you're needing more air, not less.
I don't see anything abnormal in the pictures.
Is the ignition in good health? juat kinda wondering if the ignition is failing to start the fire and what your smelling is unburnt fuel going out the exhaust.
 

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As a test, if you have a different coil. I'd try it. I don't like those oil can types. I can't seem to get along with em.
If you don't have one, yours is probably fine.
 

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Try closing up the plug gap to .025
Small I know....but it's just testing.

The only way to know if the rings are seated or going to seat at all is with a engine dyno OR leak down tester.
everything else is basically a guess at best.
My best guess, your 20w oil or washed down cylinders aren't a problem to worry about right now. To wash down a hole tales enough fuel you would nearly see it dripping from the exhaust pipes.
You haven't yet said anything about how the bores were prepped or what ring your using. Based on all you have said, I don't have anything to suggest washed down walls or oil problems. I know your reaching for a problem, but I don't think this is where to concentrate your efforts.
I suspect, you have two problems. The first is a slight over fueling problem AND a ignition problem failing to start the burn consistently, or completely, as in it may begin to burn but blows itself out leaving traces of fuel in the exhaust. That is why a new set of plugs and closing up the gaps are my suggestions. The smaller gap is easier to jump for the ignition system.
Leaving the timing at 36 locked is fine for now as its eliminates a variable, play with it later.

On a street application you want to pump to begin at throttle application and end as soon as the booster begin to come in.
35's are too big, 31's should be plenty, you just need to get the timing correct with the pump cams. This also assumes good healthy pump shots. Ones that fire a solid stream across the throttle bore and hit the booster hard enough to break up the stream into smaller droplets is ideal.
What color pump cams and what holes? Eric already asked.....It's important.
 

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Simple.
ignotion lead is added to start the burn process early enough that maximum pressure is produced when the piston/rod/crank is position to make best use of it.
Give it what it wants.
With mechanical devices, we have to compromises to make. We sacrifice slow speed timing for proper timing at high speeds and a curve is the best way to adjust it with the weights and springs. When electronics take over we don't have the same compromises so you can make it whatever it
Needs to be for the throttle angle, rpm, and loads.
On our competition engines we always lock timing to whatever makes best power. Nothing else is a concern.
Street rides can't get away with that because high timing and high loads break things.
Imma say use the electronics to the best you can to get the timing that makes the most power at all loads and rpm's you need.
Thinking modern computer operated cars. There's enough information being fed to the timing gods that can give the timing curves at 100rom increments, at all throttle positions and engine loads from 750-redline. You can't do that with a dist only looking at rpm and vacuum, but you can realize you have more control than the weights and springs of yesterday and it's one direction progressive style graphing curve.
 

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Its been stated 100 times before you MUST SORT OUT THE IGNITION before you do anything with the carburetor.
Many "carburator problems" are related to a poor ignition. I've said it up there....others have said it.....believe it....
When you get your plugs in, you'll need to go back and do the carb over again.
 
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