hazard2k

The basics:
Well my car is making what sounds like a combination of the rockers tapping the valves, and a metal scraping metal sound. It sounds like it is coming right from the back of the alternator, so i took the belt off and its still there. I took the valve cover off and nothing appears to be broken, and all the rockers are tight, and the lash seems to be fine.

The details:
I got off the expressway after doing 75 for about an hour. I get to a red light and rev my engine at my friend. This is when it started. It mainly does it around 2500 RPM, at idle it is not present. If you are driving around 60-70 just cruising along, you will not hear it. If you let off the gas, or give it more gas, the sound becomes VERY noticable.
I let it sit for a few days, and then i drove it to my shop to change the oil before i started tearing into it, and when i got there i noticed the sound was gone. I drove it for around 5 days and it was fine. Sunday i went to the store, came out and started my car, and the noise came back. The noise is still there currently.

It sounds like i coming from right behind the alternator, so im assuming its valvetrain noise, but when i take off the oil cap it does not get louder, like i think it would if it was inside the valve cover.

What things should i check? Anybody have any idea on what could be causing this? Thanks -Jeff

Robs97Z28

I would check the oneway check for the air system. it is behind the alt.. It is there to prevent exhaust from coming back into the air pump. it will blow exhaust out if it is bad and might even make noise.

hazard2k

Thanks for the reply.. but i have long tube headers with no air, so that elinimates that. Any othr suggestions?

atlasengr

Same situation on my 96 Z. I've been researching LT1 Tech and the noise I hear "marbles in the intake" seem to point towards ROD KNOCKING.

The sound appeared one day out of the blue. Had it parked for a month, removed the intake, checked the lifters, pushrods, and adjusted rockers -- then the car was turned on. It worked great for 6 days and now the noise is back -- those damb marbles !

Hopefully someone can help both of us out. I can take a MPEG video later on today and email it to someone who can tell what the exact problem is once the sound clip is heard.


-PL

hazard2k

My sound does sound like marbles, just like you are describing, but mine sounds like its coming right from the PS valve cover, right by the alternator, not in the intake... Possibly the same problem? Could this problem go away and return like it is?

robertotrevino

did you fix it? my car is doing the same.