A loud pop, then smoke

[Softballer77]

So I ran another rally on Saturday which took us through Death Valley. Speeds got up there for long durations of time. I have 4.10s. I don't have track pack. I kept my eye on all my parameters and noticed the oil temp higher than usual but still in the green. During a top speed hit, I hit 177 in 5th. Right at that moment I heard and felt a loud pop under the floorboard and then saw dark smoke come out of the exhaust for a little bit. I immediately let out and coasted to a stop. Car came down to idle fine. I let it run for about a min just to let temps come down then shut it down. Look under car, no drips of anything. Brakes were a little steamy as we were averaging 130-140 for a good 50 miles or so, and slight smoke at the fire wall but again...nothing else. Started car, ran fine, no smoke but took it easy till getting to vegas. Drove next day and she drove just perfect. Got into it a few times and not a single hitch. Anyone have any idea what that was? Maybe was past the 6250 mark for longer than 8 seconds and it did a fuel cutoff on me maybe?

Confused!

 

[Snoopy49]

I wonder if you destroyed a CAT?

 

[Softballer77]

I wonder snoop...but wouldn't I get a cel?

 

[Blackdevil77]

Wow, that's really strange. Maybe your car sucked up a furry animal and farted it out. I'm curious to know what that could have been also. Only thing I can think of is what snoop said with the cat.

 

[93 347 Cobra]

Sounds like a kickass time! Did you happen to notice you A/Fs during those high speed blasts?

 

[Softballer77]

They looked fine most of the drive, but admittedly when I noticed the oil temp getting up there, I clicked that so that I could see it solely for just a bit (the actual needle gauge. So I didn't have the others up to be seen at that moment.

It certainly was a kick ass time! We do it about every 6 weeks or so. Life in Sixth Gear is the group out of SoCal. However, I just got to Kentucky for business today and will be here for a good 3 months. Having the Shelby shipped out here in a couple days. Hoping to meet up with some peeps from this area...

 

[Bad Company]

I'm wondering the same thing Snoopy. High heat, high RPM and high engine load all at once and a cat said ouch

 

[2011 gtcs]

Its very possible you had a bad back fire, that would explain the black smoke, but it's impossible to tell. If you did destroy a cat you may not set a check engine cause the cat may be clogged up, or it will take a couple days to set. if everything is running good than isn't much you can expect keep driving it.

 

[carguy19]

If there was enough black smoke for you to notice it at those speeds, I would do a compression/leakdown test, has to be a ton of smoke for you to see it at 3 digit speeds.

 

[freakshow12]

You didn't smoke the clutch out of it did you? A guy here with an 11 that ran Texas mile with 1150hp was doing some speed runs on his dyno and the clutch let go top of 5th gear and smoked just how you said. Perfect drivability after until you leaned on it hard. Just something else to think about

 

[Beercules]

Just in case it was a cat. .. a guy on another forum melted the cat on his saleen and plugged the exhaust on that side. His boost sky rocketed driving through his neighborhood and blew his engine. Exhaust had to go somewhere.

Until you know for sure it's not a cat...if you see your boost jump for no reason shut the car off inmediately.

 

[Softballer77]

UPDATE:

The car arrived via carrier to me in Tennessee last night. Took it in to get the windshield replaced (road debris from rallys), then took it across the street to put it on a lift and check everything out.

Tranny fluid spray. The "expert" there told me (after I gave him the story) that basically the tranny under such a load and no doubt heat blew the pressure relief valve on the top side of the tranny, thus spraying fluid on the hot exhaust which is where the smoke came from and why i felt a "pop" on the floorboard by my right foot. Now, he told me that once this relief valve or whatever it actually is relieves pressure, that it is made to self seal right back up immediately.

The story makes sense to me, but wanted to run it across those here to see if it's concurrable. Otherwise, he said it's just fine. I did have the clutch replaced about 3 weeks ago, and perhaps they topped off the fluid. Maybe it was a little overserviced as well. IDK. Anyways, let me know what you guys think.

Thanks.

 

[scotsam]

It's not a relief valve it's a vent so there should be no pop it is or should be open all the time. The fluid getting hot and burping some out makes sense but it still doesn't explain the pop.

 

[Snoopy49]

Unless he blew the cap off the vent.

 

[Bflorhaug]

when it was in the air, did you actually see any burn marks on the exhaust from where Transmission fluid could have hit it? Or any fluid on the bottom floor boards? if there is nothing there, and with a good eye on looking for that, I would say its not from your transmission. I have had similar problems on my 96' cobra. Granted diff motors etc etc, but I ran a data logger and actually seen that after a 6.5k pull I ended up having a valve floating issue on cylinder 6. Heard a pop, seen the smoke, everything worked fine afterwards, granted I ended up redoing my valve train from the previous build. But for the floor board thing : / Without having the vehicle in front of me, anyone's guess could be the problem.

 

[Softballer77]

when it was in the air, did you actually see any burn marks on the exhaust from where Transmission fluid could have hit it? Or any fluid on the bottom floor boards? if there is nothing there, and with a good eye on looking for that, I would say its not from your transmission. I have had similar problems on my 96' cobra. Granted diff motors etc etc, but I ran a data logger and actually seen that after a 6.5k pull I ended up having a valve floating issue on cylinder 6. Heard a pop, seen the smoke, everything worked fine afterwards, granted I ended up redoing my valve train from the previous build. But for the floor board thing : / Without having the vehicle in front of me, anyone's guess could be the problem.

I didn't see burn marks as I wasn't able (or had a mirror) to look on the top side of the exhaust, however it was 100% sprayed on the trans tunnel just above the transmission as it was still wet there. It was enough to where I could see some on the heat shield as well further down next to where the exhaust is, so no doubt it hit the exhaust.

Interesting about the valve float, however feeling it under my foot kinda deters me from thinking it was a valve issue.

 

[paluka21]

I didn't see burn marks as I wasn't able (or had a mirror) to look on the top side of the exhaust, however it was 100% sprayed on the trans tunnel just above the transmission as it was still wet there. It was enough to where I could see some on the heat shield as well further down next to where the exhaust is, so no doubt it hit the exhaust.

Interesting about the valve float, however feeling it under my foot kinda deters me from thinking it was a valve issue.

I wouldn't think you have valve float, as this would be more common when running high RPM loads, or even with aftermarket cams with inadequate seat pressures for the valve springs. Given that you witnesses fluid under the car, it sounds like the mechanic may have been right. But, if it were my car, I would leak the motor down anyways just to be on the safe side. Not sure how difficult it would be to leak down this motor, but on my old 331 it was cake with the right tools. (leakdown gauge, air compressor, toilet paper, small flat head screw driver, 1/2 drive wrench and socket to turn the crank, and removal of spark plugs)

 

[tomshep]

If possible, check the vent and see if they damaged it when the tranny was installed. The vent should not have pressure. However, they may have hit it on the tunnel during installation and it is building pressure. If it is, you need to get it fixed or your will end up damaging seals and have a leaking tranny.

Tom