hey guys, i just dropped in a new 383 crate engine. I have a 91 z28 and i also put on a complete exhaust from headers to y pipe to flowmaster muffler. The problem is that there is a rattling noise when the car is idling. I can't pinpoint exactly where it is, though i've narrowed it down to the area near the oil pan. The y pipe is tucked very close to the oil pan but i can't tell for sure if it's making contact. I've looked around the entire undercarriage and can't see if anything is hitting. The rattling almost sounds as if it's the motor but i believe it's something else. Sound travels and is not easy to track exactly. Also, I've never heard any engine with any problem that would sound like the rattling that i hear. I removed the cover to the converter to see if anything got loose and i don't see anything. It rattles only around 1000 rpm, but as soon as i raise the rpm above that it goes away. The engine smoothes out and the noise dissappears. I'm hoping it's not engine related, The machine shop is very reputable and they broke the engine in and dynoed it twice. The noise is not constant, it comes and goes. Any ideas?

 

i'm just hoping that it's not the motor, i've never heard an engine sound like that. It seems like a vibration towards the rear of the oil pan. I was under the car with the car idling and the flexplate seems to be straight and not wobbly.

 

found it!!!!

 

what was the noise? I have a similiar sound in mine when it idles.... doesnt make a noise above 1000 rpm.

 

it was the pipe coming down from the header that connects into the y. The piece that runs under the oil pan was making contact at low rpms. I wedged a screwdriver between the pipe and oil pan and the noise dissappeared.