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3.8 Surpercharged Engine Knock.

B

bigmike0071

New member
I have a 1997 Grand Prix GTP supercharged. I was driving down the road and it started to lose power and knock. Now it appears to be knocking from the lower end and has a slight miss. Does anyone have any idea what direction to go?
 


I don't think it needs a new motor, it still runs. The knock does get louder and a higher RMP. I think I saved the motor by shutting it off and having it towed. My neighbor thinks that it has a broken piston but if that was the case I am sure the knock would be really loud and the car would not run. It is coming from the back passenger side of the motor, I am unable to tell if it is coming from the lower end or the top end. It sounds like its more in the middle.
 


This motor ran, yes one completely missing piston.
IMG_4653.jpg


The piston
IMG_4670.jpg


From your description, you spun a bearing. If you spun a bearing the most cost effective way is to replace the motor. These motors are not tolerant of replacing bearings w/o machining the crank and piston rods etc etc.
 
unless you like repeatedly rebuilding motors and pulling them and reinstalling them, get a different bottom end and be done with it. If you dont, you will be known as GTPJOE Jr. from here on out....
 
or kfish :)...3rd times the charm though. Get a new bottom end. Hell of a lot easier and cheaper IMO
 




Zef_66 said:
So yeah, you are doing something wrong.
Click to expand...

Not really...it is just the fact that every bottom end I bought has been a HIGH mileage motor...I'm too cheap to just go buy a nice one...and I'm not really on 5...it actually boils down like this...

2/2007 - Bought GTP
12/2007 - Lost motor to ZZP PCM...shattered the 3rd piston like no ones business...
3/2009 - Lifter failed...mucho internal damage...
6/2009 - Injector failed...cylinder #4 leaned out so far it turned everything white and melted the spark plug in the head, and the valve head was non-existant.

So...I guess not even high mileage blocks...just the fact I have REALLY bad luck. The one in March could have been prevented IMO...it had a lifter tick...but apparently it was A LOT worse than it sounded.
 
bluegtp91 said:
Not really...it is just the fact that every bottom end I bought has been a HIGH mileage motor...I'm too cheap to just go buy a nice one...and I'm not really on 5...it actually boils down like this...

2/2007 - Bought GTP
12/2007 - Lost motor to ZZP PCM...shattered the 3rd piston like no ones business...
3/2009 - Lifter failed...mucho internal damage...
6/2009 - Injector failed...cylinder #4 leaned out so far it turned everything white and melted the spark plug in the head, and the valve head was non-existant.

So...I guess not even high mileage blocks...just the fact I have REALLY bad luck. The one in March could have been prevented IMO...it had a lifter tick...but apparently it was A LOT worse than it sounded.
Click to expand...

Wow. Confused now how many motors you went through and what exactly was the cause of it all. Maybe that was your angle. :th_scratchhead:

Either way, sounds like you are to blame for a lot of it. ;)
 
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