Motor noise ?

[AR67GTX]

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

 

[67 B-body]

Could it be the fuel pump pushrod??

 

[70rr-brian]

Maybe heat riser in stock manifold? Bad spring?

 

[RustyRatRod]

Is it one knock or is it a rattle like a diesel? Almost sounds like some light piston slap. Does it improve when it warms up? If it gets better with temperature, my money is on piston slap. If that's what it is, it's harmless. Most honest HP engines have it to some degree.

 

[Garys1969RR]

That low note thumping sound seems to be common to all the 440 s I ever had. Most likely cause is fuel pump as 67 said. Or maybe piston slap as Rusty said. I naver had any problem develop from it, but it is strange sounding.

 

[AR67GTX]

Is it one knock or is it a rattle like a diesel? Almost sounds like some light piston slap. Does it improve when it warms up? If it gets better with temperature, my money is on piston slap. If that's what it is, it's harmless. Most honest HP engines have it to some degree.

I've been struggling for a good description for it - but you have hit on a perfect one. It sounds like a diesel idling - perfect description although not quite as loud as most diesels. slightest touch of the throttle and it goes away. Absolutely no rap or knock as it leaves idle and revs up.

No heat riser on the car (removed). From my experience I don't think it's piston slap. As soon as the car is started and settles to normal idle speed you can hear it. It doesn't get any better or worse as the motor warms up. I think piston slap tends to decrease as a motor warms up and pistons expand.

What would be the issue with the fuel pump pushrod? It was suppose to have a brand new stock Magnum cam when it was rebuilt. Would replacing the pushrod possibly help or is it likely the cam eccentric?

Thanks

 

[Dennis H]

Well I feel better about my piston slap now. Let us know if you pinpoint the cause on yours.

 

[shag766]

i have the same thing with my hemi. it had about 700 miles on the re-build when i got it and has been there since i first fired it. in my mind i have been writing it off to solid lifters. if it seems to be a uniform rattle across the board i would guess that would rule out the fuel pump rod.:eusa_think:

 

[AR67GTX]

I'm still curious about the fuel pump push rod. That would be a fairly easy replacement. I assume it is under constant load with no lash from the fuel pump arm and spring. But maybe there is something there I'm not thinking of??

I will see if I can video it and if the sound will pick up on the recording.

Thanks

 

[67 B-body]

I'm still curious about the fuel pump push rod. That would be a fairly easy replacement. I assume it is under constant load with no lash from the fuel pump arm and spring. But maybe there is something there I'm not thinking of??

I will see if I can video it and if the sound will pick up on the recording.

Thanks

Well,,,, they have been wearing out for some guys because of the crappy oil they ran... It can be destroyed just the same as a flat tappet "hyd or solid" lifter if it doesn't seat correctly. Then you have a pulsating noise "tick tick tick tick" deeper inside sound. Also, you could have lower fuel volume as a result of lesser travel against the fuel pump arm... It's slight, but the potential would be there...

 

[RustyRatRod]

If it sounds like a diesel as you describe, then it is more than one thing makin the noise. That's why it sounds like a diesel. It's probably all eight. Unless it gets worse, screw it. Drive it like you stole it. Some motors don't exhibit piston slap getting better as it warms up. Most do, but not all. That sure sounds like what it is.

 

[AR67GTX]

If it sounds like a diesel as you describe, then it is more than one thing makin the noise. That's why it sounds like a diesel. It's probably all eight. Unless it gets worse, screw it. Drive it like you stole it. Some motors don't exhibit piston slap getting better as it warms up. Most do, but not all. That sure sounds like what it is.

That's pretty much what I have been doing - driving it for about 10 years this way. I've been to a couple cruise nights lately and get tired of people asking - Hey man, whats up with your motor?

Here is a video with sound. I think this actually amplifies the sound a little. Maybe it will help confirm the issue or generate some new ideas.

http://s125.photobucket.com/albums/...ngine noise/?action=view&current=MVI_1644.mp4

 

[shag766]

listened to you video and it sounds like a knock, sort of, not an even sound. just guessing but maybe fuel push rod or possibly in a/c compressor.

 

[AR67GTX]

I may try changing the pump pushrod. Hopefully NAPA can find one w/o having to charge cross-country shipping. I've dropped the belts off the air cond compressor in the past w/o losing the noise so I've pretty much ruled it out.

Thanks

Dan

 

[AR67GTX]

BTT - any other observations from the video?

 

[RustyRatRod]

That's too high a frequency for piston slap, IMO. Piston slap sounds of a lower frequency similar to a rod knock. That almost sounds like valve train. Has it sounded like that ever since it was put together.

 

[dryheat]

My first impression was valve train also. I would pull the valve covers and just check around for any obvious signs of abnormal wear & tear ... bent or broken parts ... left & right rockers in the correct locations ... and repair as necessary.

Hope you get it figured out quickly.

 

[tpodwdog]

That's pretty much what I have been doing - driving it for about 10 years this way. I've been to a couple cruise nights lately and get tired of people asking - Hey man, whats up with your motor?



http://s125.photobucket.com/albums/p59/dclemans/Plymought%2067%20GTX/Plymouth%20GTX%20engine%20noise/?action=view&current=MVI_1644.mp4

when i go to any car cruise....i enter with "INNA-GADDA-DA-VIDA " blasting on the stereo at about 110 Db. try that and people will stop asking " whats wrong with your engine"......and start asking... hey dude,,,,,wanna burn one ? ":headbang:

i have heard A/C compressors make that noise you describe. do you have a stethoscope? if ya do ....put it all over the motor until you find it.....if you dont have a stethoscope....get a coat hanger....bend one end on a tight loop and stick it in your ear....take the other end and commence to lookin for the noise. TRY NOT TO GET IT CAUGHT IN THE FAN.....that could be messy !

 

[AR67GTX]

It's been this way as long as I can remember. I can't say for sure that it was this way when I bought it about 2001. The motor had been rebuilt before my ownership. As noted above I replaced the rocker shafts at one point and I have removed all the belts from the engine as a test. There was a period of time up until about 2005 that I ran Mobile 1 oil in it before switching to 15W-40 diesel oil. It might have gotten some cam wear from the Mobile 1. It's hard to tell by the video but when the motor is revved up - it's smooth sounding with no strange tapping, knocking or rapping. I would think valve train noise would actually get worse?? Maybe not?

I appreciate everyone chiming in with suggestions.

 

[AR67GTX]

when i go to any car cruise....i enter with "INNA-GADDA-DA-VIDA " blasting on the stereo at about 110 Db. try that and people will stop asking " whats wrong with your engine"......and start asking... hey dude,,,,,wanna burn one ? ":headbang:

i have heard A/C compressors make that noise you describe. do you have a stethoscope? if ya do ....put it all over the motor until you find it.....if you dont have a stethoscope....get a coat hanger....bend one end on a tight loop and stick it in your ear....take the other end and commence to lookin for the noise. TRY NOT TO GET IT CAUGHT IN THE FAN.....that could be messy !

I may have to find an old 8-track and try that.

I've tried a stethoscope but didn't have any luck. The noise seems to telegraph all over the engine. Maybe that alone points to some sort of valve train issue.