About to throw a rod???
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 834
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From: Keller Texas
About to throw a rod???
I have 96 LT4 and thing are looking bad! Last night I started hearing a loud knocking noise from the motor at about 2500RPM. It sound bad and it sound like some where in the rotating ***. from the bottom of the motor. It does still run and seems to run fine other than that. Is it about to throw a rod? Any idea of who to take it to in the DFW area who knows Vettes? Any ideas will help. 
Race Director
Joined: Feb 2004
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Not good. I would not recommend driving it. What you could try is remove 1 plug wire at a time and see if the noise quiets down on a certain cyl. If it does you will confirm the rod bearing and locate it at the same time. Did oil pressure drop 10 lbs or so?
Thread Starter
Burning Brakes
Joined: Nov 2004
Posts: 834
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From: Keller Texas
Originally Posted by Pete K
Not good. I would not recommend driving it. What you could try is remove 1 plug wire at a time and see if the noise quiets down on a certain cyl. If it does you will confirm the rod bearing and locate it at the same time. Did oil pressure drop 10 lbs or so?
No from what I can tell it did not! So it could be a bearing on the rod? The knocking noise is not heard until the RPM are brought up to 2500 and it get louder with higher RPMs. So we shut it down until we can figure out what it is.If it is a rod bearing,what are we looking at in repairs as a min. Can I just replace the one rod and piston or are we talking a bottom end rebuild? Money is a serious issue here!!
Race Director
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A best case situation will be checking the rods big end , checking the rod journal and if all is good new bearing. A worst case is turning the crank undersizen rebuilding rods and all new bearings. Option 1 is not typical. Sorry for the bad news. Lets not panic yet, we need a positive diagnosis for sure. Have someone with a stethascope listen. A trained ear will pick up the problem.
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From: St. Peters MO Sometimes you have to prove yourself by doing alot of killing or alot of dying...
with Pete. While your problem 'appears' to be rods or bearings... the proper diagnostic must be done to be sure. When the noise occured, was it under acceleration? I know one easy way to check for lower end damage while on a test drive is to run the motor to 4k in any gear and let off the throttle while still in gear. A rod noise generally appears at or around 2500-3500. While this is okay when test driving someone elses car, it may not be wise to do to your own... just food for thought if you can recall any specifics.
Thread Starter
Burning Brakes
Joined: Nov 2004
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From: Keller Texas
Originally Posted by kwik_ta
with Pete. While your problem 'appears' to be rods or bearings... the proper diagnostic must be done to be sure. When the noise occured, was it under acceleration? I know one easy way to check for lower end damage while on a test drive is to run the motor to 4k in any gear and let off the throttle while still in gear. A rod noise generally appears at or around 2500-3500. While this is okay when test driving someone elses car, it may not be wise to do to your own... just food for thought if you can recall any specifics.Well the knocking noise is coming in at around2500! It gets louder with RPMs going up. You can feel the knocking on the motor as well. I did try running it and think it is the #7 cylinder. I pulled the plug wire and it seemed to be alot less after doing it on that cylinder. I have drained the oil nad will pull the pan tomorrow and check it then! At leaste it did not through the rod and trash the motor. It is still repairable!!
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Originally Posted by RED LT4
Well the knocking noise is coming in at around2500! It gets louder with RPMs going up. You can feel the knocking on the motor as well. I did try running it and think it is the #7 cylinder. I pulled the plug wire and it seemed to be alot less after doing it on that cylinder. I have drained the oil nad will pull the pan tomorrow and check it then! At leaste it did not through the rod and trash the motor. It is still repairable!!
