I have a stock 440 Magnum engine in my GTX and it has always had a strange, muted rattle only at idle. It's not a sharp, mettalic sound. Almost sounds a little like the sewing machine solid lifters noise but not quite. It's there as soon as the engine falls off fast idle from a cold start so the temp of the motor oil doesn't make any difference. Otherwise the motor runs great, smooth, good oil pressure, and no oil use. it pulls strong on acceleration. Yank the throttle and the rattle instantly disappears - no knocking of any sort, and reappears as soon as it hits idle again.
Thinking the rocker arm shafts might be worn (and they were installed upside down as I remember) I replaced them a few years ago without any change. I've dropped all the belts off the accessories and run the motor and that hasn't revealed any change. I remember when I first bought the car about 10 years ago I pulled and replaced the oil pan and at the time noticed that the rods seemed to have a lot of clearance. I thought it odd at the time but I was fixated on replacing the oil pan and didn't think to get a dial indicator out and check the play. But, I'm not good at judging clearances by eye and since I have good oil pressure - about 25 psi at idle and 50 psi at 2000 rpm - I'm not really sure it's excessive. I've tried an engine stethescope but haven't had much luck pinpinting anything with it. It definately maginfies the rattle but seems to pick it up over the whole engine.
Just wondering if anyone might have run across a strange sound like this in their 383/440 and have an idea of what this might be.
thanks
Thinking the rocker arm shafts might be worn (and they were installed upside down as I remember) I replaced them a few years ago without any change. I've dropped all the belts off the accessories and run the motor and that hasn't revealed any change. I remember when I first bought the car about 10 years ago I pulled and replaced the oil pan and at the time noticed that the rods seemed to have a lot of clearance. I thought it odd at the time but I was fixated on replacing the oil pan and didn't think to get a dial indicator out and check the play. But, I'm not good at judging clearances by eye and since I have good oil pressure - about 25 psi at idle and 50 psi at 2000 rpm - I'm not really sure it's excessive. I've tried an engine stethescope but haven't had much luck pinpinting anything with it. It definately maginfies the rattle but seems to pick it up over the whole engine.
Just wondering if anyone might have run across a strange sound like this in their 383/440 and have an idea of what this might be.
thanks