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A noise reminiscent of valve clacking

Posted: Tue Dec 17, 2013 3:12 am
by astrovanfan
Hi Everyone, I know there are a ton of threads out there on rattling noises etc. I read em all and my sound, like valves clacking, is in some ways similar to other posts and in other ways it is not. I was hoping the great Astro minds here might help me diagnose the problem. Here goes. Any and all advice greatly appreciated.

Its a 1991 Astro AWD with about 175,000 miles. I keep her in Mexico where I have a little retirement casa. For running around town its great. After 6+ months of storage per year it starts right up and purrs like a kitten. No odd engine noises, not much smoke, uses a tiny bit of oil, good power etc EXCEPT when I go uphill under load and high rpms - then it clacks like a castanet and loses power. It sounds like valves but I'm just not sure. Oil pressure is good. Mileage is decent. Compression is ok. The Service Engine light comes on once in a while if I drive it more than 50 miles at a time. Not coming from the catyl converter. I'm thinking timing chain or a top-end job but in all honesty, I'm kinda perplexed.

Any suggestions? I'm a decent wrench (but mostly motorcycles) but I don't have access to modern mechanical facilities or code scanners. My options are a yard engine (from US), fixing this engine (parts difficult to get), letting her go to a nice Mexican family for cheap.

Cheers, Keith