Caravan '89 3.0 Auto+OD, Loud rattling Noise from Engine

HI Guys, Hope to get some help with my 1989 Caravan 3.0 Mitsubishi, Automatic with overdrive(3-4 speed? P-R-N-Overdrive-Drive-L). Makes a rattling noise
I went for a camping trip, about 300Km away. It was fine all the way, ate a little oil, but i refilled to proper level. On the way back, somewhere after the last stop ~100Km away from end, on the trafic lights noticed/heard this bad noise from engine when reached the city(so at the end really).
It happenes at all revs, mostly between 1-2KRPM, i don't think it is the transmission, even at park when reved it makes that rattling noise. I'm pritty sure it is from the engine, possibly the back/passanger side of the engine. To describe the noise: it sounds like a bad mufler(you can hear the combustion intervals), somewhat metalic, low frequency not high pitch, resonating with revs to the point of ear pluging like in a danceclub (althought i don't feel like dancing).
I was thinking it might be the timing chain/components OR the valves/lifters/etc OR Camshaft/Driveshaft/rod bearings.
To bring you up to speed, i had this van for ~2months, it had 282K Km on it now 284K, rebuilt(somewhat don't have much supporting paperwork on what was done) engine and transmision at about 200K. When i got it it had a rusted tiny hole in the oil pan(i replaced) and it had a rattle onece in a while, which went away after i serviced the van when i got it(oil & filter & pan, rear pads and drums, drive belt, air filter, spark plugs, trans oil, removed the dead AC and all components and other body parts like chrome bumpers rear gate etc) all in all this van had cost me a total of CND$900(price, parts and registration). I had another 1989 Caravan 4 cylinder that the trans had died and the engine was eating oil 1L/100km, it is at the junkers now after 250Kkm, all the good parts are on this van now.
so what you guys think is wrong with it. Please i need help, don't mind doing it myself, i'm thinking of going to my old mechanic, which i didn't see ever since i started doing my own work on the 3-4 cars in the family.
thanks in a dvance Ilia
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Without hearing the noise it could be anything (except a timing chain). That engine uses a belt.
Glenn Beasley Chrysler Tech
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I will try and record it, but what usually failes that can cause this kind of noise. I know it could be anything really, just hoping for past experience of someone here.
so you say it is a timing belt not a chain? is it the one under the plastic cover, almost paralel to the accesory belt?
thanks Ilia
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Yes, and the water pump is there also

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well you know how i mentioned this noise sounds like a bad mufler, well cuz it is. Went to my mechanic, he helped point out that the noise is from the exhaust pipe, his words were "the cat converter guts have colapsed and all that shit hit the mufler" that's why i hear this low frequency mufler noise at about 1.5KRPM.
Now this brings another question to my mind. Can i stick any cat converter and mufler in there, the bigger the better right? I can weld the pipes with my dad, so i'm thinking i go to junker and get my hands dirty.
Do you guys know if anything other than the pipe diameter and the shape of the exhaust/cat matters(so as long as it fits and was made for a large engine like mine V6 it should be ok, right?)?
thanks Ilia
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Ok another follow up, hope this helps someone with same problem. Basically the noise was comming from the downpipe of the exhaust. I believe that the mufler was "cloged" so it would create back pressure which resulted in loud noise in the downpipe. I confused it with the valves malfunctioning because the backpressure was effecting the clearing of the cylinders on the up stroke from exhaust, so the "booms" were prity high in the exhaust channel. Lucky me, my mechanic was very close to identifying the problem. I went to a junk yard(for the first time), it is like going on a vacation for me, i loved the place something magical in the air there. anyway took off a muffler from a ~1992 caravan 3.3L(apperantly the junkyard removes the catalitic as a recycling process, non of the cars ha a catalitic on them), cost me CND$20, even had the u clips on it(didn't get charged), and lucky me the catalitic was fine in my car(didn't colapse like my mechanic expected). Went with my dad to his work, he welded the new mufler, patched a couple of holes, made a new bracket for this slightly bigget mufler, i installed everything and helped here and there with the cutting and drilling and holding. and presto noise is gone, car is quite as was before. by the way Canadian tire was quoting me ~$500(for new exhaues from cat to pipe, and mufler alone is $100). So do the work yourself and you will save. thanks for your attention and help guys, i like this google groups thing. Ilia
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