L98 QUESTION???
Thread Starter
Instructor
Joined: Feb 2001
Posts: 199
Likes: 0
Any info would be greatly appreciated.
I purchased an 1989 Corvette with 30,000 miles it know has just under 50,000. Ever since I owned the car the engine always makes knocking noises at idle? Is this normal for this engine? I know the L98 tend to be a "rough" engine as compared with an LT-1. I've done some bolt on's, but I don't think this has any real affect on the engine noise. Also I installed a centerforce DF Clutch it was told to me that the throw out bearings tend to also make noise (a different one though) I autocross the car a lot and driver schools/time trials. Any L98 experts out there...I can really use your help.
thanks,
Ben
I purchased an 1989 Corvette with 30,000 miles it know has just under 50,000. Ever since I owned the car the engine always makes knocking noises at idle? Is this normal for this engine? I know the L98 tend to be a "rough" engine as compared with an LT-1. I've done some bolt on's, but I don't think this has any real affect on the engine noise. Also I installed a centerforce DF Clutch it was told to me that the throw out bearings tend to also make noise (a different one though) I autocross the car a lot and driver schools/time trials. Any L98 experts out there...I can really use your help.
thanks,
Ben
Burning Brakes
Joined: Apr 2001
Posts: 844
Likes: 3
From: Kennewick, Wa. USA
The L-98 is not a "rough" engine when compared to the LT-1. It's just limited in it's ability to breath at high rpm's compared to the LT-1. Knocking is a very vauge term! Can you be more specific about how it sounds and when. A bad throw out bearing does not make a knocking sound, and will usually change or go away when the clutch is engaged. Does the knocking change with rpm's? Can you tell where it's coming from...ie deep in the lower area of the block etc? Try and give a little more info!
Thread Starter
Instructor
Joined: Feb 2001
Posts: 199
Likes: 0
For the most part when the clutch is engaged the noise from the throw out bearing dissapears.
As for the "knocking" at idle and only at idle (at least as far as I know) it almost sounds like there is somthing moving or clunking around inside. I'm not a mechanic so I can't give specifics as to where or how the noise can be described. Sorry. I do know that it's loud and when I run the car at an autocross It tends to get louder, but only at idle. When I accelerate it's smooth. Hope this helps
As for the "knocking" at idle and only at idle (at least as far as I know) it almost sounds like there is somthing moving or clunking around inside. I'm not a mechanic so I can't give specifics as to where or how the noise can be described. Sorry. I do know that it's loud and when I run the car at an autocross It tends to get louder, but only at idle. When I accelerate it's smooth. Hope this helps
Originally Posted by Ezgoin721
The L-98 is not a "rough" engine when compared to the LT-1. It's just limited in it's ability to breath at high rpm's compared to the LT-1. Knocking is a very vauge term! Can you be more specific about how it sounds and when. A bad throw out bearing does not make a knocking sound, and will usually change or go away when the clutch is engaged. Does the knocking change with rpm's? Can you tell where it's coming from...ie deep in the lower area of the block etc? Try and give a little more info!
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Safety Car
Joined: Apr 1999
Posts: 4,623
Likes: 2
From: Ohio
bwagman, it sounds like the "knock" you're hearing based on the shred of information presented, may be related to your flywheel. If you're in the car at rest with the motor running and the "knock" sound changes when you engage and disengage the clutch, it's related. Did you install or have the clutch installed? Did it sound differently before? Factory flywheel, Camaro flywheel, or aluminum FW? If not dual mass factory FW, this would also be a high % cause. In any event, if that's it, you don't likely have a real problem. More details would help.
Melting Slicks
Joined: Aug 2000
Posts: 2,388
Likes: 42
From: Murrysville PA
I agree with H rocks. My 89 had a knocking noise at idle that would go away when you pressed the clutch in. It was the dual mass flywheel. After I dragged raced it, it really got bad and I had to replace the flywheel. Keep us posted.
Jason
Jason
