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Odd Rattling Sound

wh1278

wh1278

Member
While my 440 is at idle (and not in gear), there is a rattling sound like ball bearings rolling around in a can. It seems to be coming from the front of the engine. Getting my ear as close as possible without getting snagged by belts, it seems to be coming from the vibration damper area. Could it be the damper, timing chain? Oddly it seems also loud on the top near the distributor. Could it be the distributor to crankshaft gear? Or something deeper like camshaft bearings? Any experience with this would be helpful.
 
My first thought was that the sound is coming from the other end--the damper plate. That happens only at low speed, usually in neutral, when the motor is idling roughly (or too low--same difference). But you insist it's from the front....

Sounds like it MIGHT be a loose timing chain. How many hours on the motor?

Jeff

PS: Locating sounds is tough. When I'm POSITIVE that left front wheel bearing is the one that's howling, it's sure to be the right rear!
 
Try this...get a long screw driver, & I mean a long one, put the tip on where you think the noise is coming from & your ear on the handle..kind of a crude stephoscope, works surprisingly well
 
Last time I had a funky sound like that up front on one of my 440s was the dual pocket raw water pump but could be anything. Is the sound all over the place, as in not steady or is there a very specific rythm to it? Does the frequency of the rattling increase with RPM? does it ever go away at a particular RPM? If you put a timing light on the engine at idle, would the rattling be at the same speed as the light or twice as fast? What is your idle RPM?
 
Thanks. I thought it might be a pump, so I first started with the raw water pump belt. Took it off and ran for a few seconds. Sound still there. Since the sound is closer to the fresh water pump side, it might be that. Would the alternator make that type of sound? It is possible that the sound remains at higher than idle (about 800), but I cant hear it over engine noise. I am thinking timing chain is possible. I realize that a damper plate rattle might make its way to the front of the engine, but I've heard that sound before when my engine was running really bad...that makes the trans make all sorts of noise. As far as the rhythm, it sort of comes and goes a little. Sometimes worse than others. Its not consistent with the timing. How hard is it to get a look at the timing chain? Whole front end off? Can it stay in the boat?
 
Very difficult to pull the front of the motor off---and you'd want to replace the timing chain if you did, regardless.

Suggest you pull the belt off the altenator as well and run it.

Jeff
 
Did you try Pete's suggestion? If not, you'd be suprised what noises you could isolate with a long screw driver or even a broom handle!
 
Not sure about those 440s but the 318s have the fuel pump mounted on the cover and you can peek in there maybe and have a look at the chain
 
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