Rebuilt LS1 exhaust smoke after dyno pull
09-18-2015, 01:40 AM
#1
Rebuilt LS1 exhaust smoke after dyno pull You Texas guys are always super helpful so I am posting this here also.
My tuner noticed some detonation so we couldn't finish the tune, after looking at his trends he concluded that It was probably clogged injectors. There was low fuel flow to one side of the motor. So I towed the car back to my engine guy to replace the injectors and fuel pump. later that night I watched the video of the pull and sent it to my tuner who wasn't paying attention at the time of the pull and and he said that wasn't good. The block is a fresh re-build, I was wondering if the rings had not seated properly? I drove the car less than a mile un-tuned with little to no acceleration, including on and off the trailer. Could that have hurt anything, I'm not an engine guy I don't know, all I know is I keep having minor problems and now I'm worried we'll have to go back into the block. Please let me know what you guys think, thanks.
My tuner noticed some detonation so we couldn't finish the tune, after looking at his trends he concluded that It was probably clogged injectors. There was low fuel flow to one side of the motor. So I towed the car back to my engine guy to replace the injectors and fuel pump. later that night I watched the video of the pull and sent it to my tuner who wasn't paying attention at the time of the pull and and he said that wasn't good. The block is a fresh re-build, I was wondering if the rings had not seated properly? I drove the car less than a mile un-tuned with little to no acceleration, including on and off the trailer. Could that have hurt anything, I'm not an engine guy I don't know, all I know is I keep having minor problems and now I'm worried we'll have to go back into the block. Please let me know what you guys think, thanks.
09-18-2015, 01:01 PM
#2
smoke on decel, probably valve guide seals, there is a lot of vacuum on decel and that would be my 1st guess. I would check to make sure they are installed correctly and that the right ones were used. Do you have a catch can and or vented breather installed as well?
09-18-2015, 01:56 PM
#4
Hard to tell the actual smoke color. White is water, blue is oil and black is fuel. Do you know which it was? If its oil, it could be the valve guide seals. But if its a new engine and you didn't do a proper break in then it could be something worse. The smoke didn't stop coming out of the pipes when the rpm lowered. You cant build an engine all new, drive it 1 mile and then max the rpm on the dyno. Well you can but its not good. The engine should have some run time to get things seated first. It could also be oil getting sucked into the PCV valve which will then get dumped into the intake. At high rpm, its going to see a big vacuum pull inside the intake when the throttle is closed fast, which in turn pulls from the pcv.
09-18-2015, 02:18 PM
#5
The car has 42 pound injectors and it ran so rich that I didn't want to run the car too much. The little time I did drive it or let the engine idle the spark plugs were filed out and my tuner couldn't start it. He flashed tuned it and we replaced the plugs, I recall the car smoking during whole drive but I figured it was because the car was not fully to him yet, I guess the color of the smoke was whitish to grey?
09-28-2015, 12:04 PM
#7
Either that or you fuel washed the cylinders by running it untuned with larger injectors. Too much fuel on a new engine prevent the rings from seating and kills their ability to seal the combustion chamber. You may need to have the cylinders rehoned and new rings.
Cross your fingers and hope it's the rocker bolts.
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09-28-2015, 01:16 PM
#8
I would be REALLY surprised if he washed out the cylinders with less than a mile on the motor.. especially with 42lb injectors. I've ran dozens of break in motors un tuned for leak checks etc. and Never had that problem. Also this "break in" Myth doesn't apply to these newer LS motors. These are not the old school sbc motors. You want to know the best way to break in an LS motor? put it on the dyno fresh from the build and run the **** out of it. Sounds like someone put your valve train together with their eyes closed or your engine builder wasn't much of an "engine builder"
My .02 anyways
My .02 anyways
09-28-2015, 01:53 PM
#9
Man y'all making me a nervous wreck! I've posted here also if you guys want to read some more responses and let me know what you think. https://ls1tech.com/forums/showthrea...4&goto=newpost
09-29-2015, 08:06 AM
#10
I would be REALLY surprised if he washed out the cylinders with less than a mile on the motor.. especially with 42lb injectors. I've ran dozens of break in motors un tuned for leak checks etc. and Never had that problem. Also this "break in" Myth doesn't apply to these newer LS motors. These are not the old school sbc motors. You want to know the best way to break in an LS motor? put it on the dyno fresh from the build and run the **** out of it. Sounds like someone put your valve train together with their eyes closed or your engine builder wasn't much of an "engine builder"
My .02 anyways
My .02 anyways
I built the engine in my Trans Am and drove it to Victoria untuned, but I kelt it on the stock injectors and out of open loop operation. On the dyno, I changed out the injectors and the ECU was tuned to take that into account before firing it up again.
I do think it's more likely that the rocker bolts don't have sealed on them, but I wouldn't dismiss the possibility that the rings may not be sealing very well.