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MustangGT

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Smokin'
« on: July 08, 2015, 06:41:33 PM »
Please have a look at this video.
Seperate O2 sensor in each header showing perfectly good and equal numbers.
Dyno operator didn't understand why it was smoking so bad. Could be soot and grime in the exhaust pipes and mufflers he suggested, but this video was taken about 2 hours into the tuning session so I would think most of it was cleared out by then?
Could it be yet another intake gasket leak? It uses some oil but I have an oil leak somewhere as well since it drips from the bellhousing.

https://youtu.be/309tPFRpLm0
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Joe-JDC

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Re: Smokin'
« Reply #1 on: July 08, 2015, 07:40:10 PM »
I would say give it more than two hours run time.  That looked rich to me, and old soot coming out of the pipes.  Yes there was a slight white puff, but I would not panic just yet.  Joe-JDC
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Barry_R

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Re: Smokin'
« Reply #2 on: July 08, 2015, 08:22:04 PM »
O2 might be reading OK but that black smoke says "rich".  Or at least unburned fuel.  O2 sensors do not directly measure mixture - they measure oxygen.  Sounds intuitive, but its sometimes easy to forget.  A misfire from detonation, or from any other cause including over richness will sometimes read as "lean" on an O2.  How do the plugs look?  If they look OK I would be tempted to pull a few percent out of the upper RPM fuel and see if its reflected in the O2 numbers.  You also need to remember that the O2 data is reading history - the events that have already happened - and they may lag on a printout - if your pull theoretically ends at 6000 the engine might be going dead rich at 5900 & up and you won't always see it...

Various fuel chemistry will have a major impact on the "correct" O2 numbers as well.  I had some crazy spec stuff at one EMC contest that ran best with O2 numbers that scared the bejeebers out of me...

It kinda pops a puff out the exhaust almost toward the end of the pull, which could be a touch of detonation unseating the rings.  If it does that a pull of smoke on deccel might not mean much of anything at all.  Once the rings become unstable the control is gone until the engine calms down again.
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MustangGT

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Re: Smokin'
« Reply #3 on: July 09, 2015, 08:37:39 AM »
Thanks for the comments.
I yanked out #4 since that is the easiest to get to. Looks rich to me...
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ScotiaFE

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Re: Smokin'
« Reply #4 on: July 09, 2015, 10:25:24 AM »
Maybe a tad fat, but I would rather be fat and cool than lean and hot. jmho
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Nightmist66

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Re: Smokin'
« Reply #5 on: July 09, 2015, 10:46:21 AM »
Possible vacuum or exhaust leak before O2 that is skewing the numbers and causing it to run rich?
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Jared



66 Fairlane GT 390 - .035" Over 390, Wide Ratio Top Loader, 9" w/spool, 4.86

Barry_R

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Re: Smokin'
« Reply #6 on: July 09, 2015, 05:48:21 PM »
Can you point the camera down the throat of the plug and use a flashlight to illuminate instead of the camera flash?
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MustangGT

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Re: Smokin'
« Reply #7 on: July 09, 2015, 06:34:21 PM »
Quote from: Barry_R on July 09, 2015, 05:48:21 PM
Can you point the camera down the throat of the plug and use a flashlight to illuminate instead of the camera flash?

Is this better Barry?
There is a limitation on the file size on this forum so I can't make it larger
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cjshaker

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Re: Smokin'
« Reply #8 on: July 09, 2015, 07:40:01 PM »
The engine flattened out hard right at the top end, right where it went pig rich, indicated by the black smoke. The puff of blue as it settled down COULD be from high vacuum pulling oil past the rings or valves, but I noted it only came from the right side. I wouldn't worry about the blue smoke just yet, but something caused it to go VERY rich right at the end, and that plug shows it. Maybe it was pulling fuel over the vent tubes.

One plug won't give you a complete picture though. I know they're a real pain to get out, but I'd want to see them all after seeing how black that #4 is. If you have one on the right bank that looks oily and not just black soot, that could explain the puff of blue.
« Last Edit: July 09, 2015, 07:41:56 PM by cjshaker »
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Doug Smith


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MustangGT

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Re: Smokin'
« Reply #9 on: July 10, 2015, 09:52:34 AM »
Yeah, something is going on. It fell flat on its face at exactly 5500rpm. The HP curve was still increasing when that happen and from earlier dyno sessions I know this engine will easily do 6000.

The #4 actually has a slight mist of oil on it from what I can tell , it is not matte black like pure soot but ever so slightly "moist".
I'll roll up my sleeves, bust my knuckles, and yank the other 7 plugs out and have a look . I'll post pics for you to see.

What also worries me is what Nightmist66 said, vacuum or exhaust leak. I can't find any evidence of an exhaust leak from the heads and the O2 sensors are in the collectors before the joint. There is only one vacuum line, going from the throttle body to the MAP sensor, and it looks good. Line is new, fittings are new.
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Nightmist66

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Re: Smokin'
« Reply #10 on: July 10, 2015, 10:25:29 AM »
Just curious which intake gaskets you used.
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Jared



66 Fairlane GT 390 - .035" Over 390, Wide Ratio Top Loader, 9" w/spool, 4.86

MustangGT

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Re: Smokin'
« Reply #11 on: July 10, 2015, 10:31:06 AM »
Quote from: Nightmist66 on July 10, 2015, 10:25:29 AM
Just curious which intake gaskets you used.

I don't really remember, sorry. I replaced them last year due to a faulty hydraulic lifter. I bought them from Survival so I guess they are good quality.
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Nightmist66

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Re: Smokin'
« Reply #12 on: July 10, 2015, 11:02:10 AM »
Hopefully it wasn't the Fel-Pro Printoleaks. ::)
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Jared



66 Fairlane GT 390 - .035" Over 390, Wide Ratio Top Loader, 9" w/spool, 4.86

MustangGT

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Re: Smokin'
« Reply #13 on: July 11, 2015, 07:12:03 AM »
Here is the pics of the plugs. The plugs look pretty consistent to me with #4 and #8 slightly moist
#1 and #2 first
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MustangGT

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Re: Smokin'
« Reply #14 on: July 11, 2015, 07:13:11 AM »
#3 and #4
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