Motor sounds like marbles
Last edited by 98cobrakillata; Apr 1, 2005 at 02:48 AM. Reason: Forgot one detail
It does sound like a loud sewing machine. The werd thing is the sound is there for a while then goes away, then comes back again.It will be very consistant then stops and becomes unconsistant for a while.
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I would inspect the flex-plate first (see below). Or...
With the mods you have, you probably know all of this:
While the covers are off, you may as well pull your plugs and inspect the rockers. Makes it easy to turn the engine by hand with the plugs out. Put a socket on the balancer and (have someone) turn the engine over slowly. Inspect the motion for each set of valves, one cylinder at a time, through all four strokes. Pay close attention to the geometry...making sure the push rods and valve stems are not bent. Make sure the lash is set properly...no slop between the rocker, valve and push rod. I don't know what the lash should be for the LSx...probably one-quarter turn passed zero lash. Check your FSM or maybe someone on the list will respond.
You will inspect lash when the rockers come to rest anywhere along the compression (squeeze/bang) stroke after intake closes and before the exhaust valve starts to open. Try and move the push rod with your fingers. You should not be able to move it up or down. Then, make sure the rockers are not moving and both valves are closed (compression TDC would be best). You can slip a plastic rod into the spark plug hole to make sure the piston is at TDC. Just be sure the rod is long enough not to fall in. Once you know exactly what the lash should be for your engine, you can loosen/remove the bolt holding the rocker to the stud (one at a time). While loostening the bolt, count the number of turns until lash is detected. Inspect the rocker. Inspect the stud and bolt. Inspect the push rods. Inspect the spring and see if it's all in one piece. Reassemble setting the proper lash and check the next one.
If all is well, unfortunately, it could be a lot of different things. The first (other) thing that comes to mind is possibly a cracked flex-plate. That can sound like a lifter. If you have no obvious effect on performance and good oil pressure, this could be a suspect. Get a mechanic's stethoscope ($5 at AutoZone) and locate the noise (engine running). If it's the flex-plate, the noise will be much louder near the trans bell housing. And, a lifter only moves once every two engine rotations. The flex-plate obviously rotates with the crank. So, if the noise is in sync with the engine, it's probably not valve related. If the noise is half-speed of the engine rpm, it very well could be noise from a valve, cam-driven or cam associate.
If you suspect the flex-plate, jack the car up on stands and get under there. If the setup is like most GM (I have never been under an F-body), there should be a cover with four bolts that you can remove to see the flex-plate. (Folks?) Again, have someone turn the engine over and inspect the flex-plate (or you could try turning the engine with a wrench on the flex-plate). Use a powerful lamp or flashlight. Cracks in flex-plates can be hard to see
Good luck and let us know what you find.
Last edited by Builder; Apr 2, 2005 at 01:32 AM. Reason: Question...
when i broke my flexplate it was topping out 3rd gear...not only did it crack, it cracked and bent and was scraping the bellhousing of the transmission or the block. it sounded horrible metal scrapping metal. no ses codes of course.
your problem doesnt seem like its the flexplate from your description. i don't see why the car would die from it and it shouldn't effect the idle speed either, but check it just to be sure.
check the flexplate, if that is ok then pull the valve covers...and go from there..
good luck





