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When I bought this 1979 motor home, it had been sitting for 3 years but they had started it up periodically. I jumped it off & drove it 26 miles home & it ran pretty good. I bought new batteries & have been starting it up & running it without a problem. I drove it 5 miles into town 2 weeks ago to get gas for it. It ran fine but on the way back, about 3 miles from home, it started knocking. I thought it was the exhaust. I got home & checked the oil & it was fine. Yesterday I flushed the motor, drained the oil, removed the oil pan (it was fairly clean, no sludge), & put new oil in. Put new plugs in also. The motor started right up. At idle, I could not hear the knocking. When I reved it up, the knocking started. At idle its almost gone. Sounds like its on the passenger side of the motor but sometimes it sounds like right under the carburator. The motor was rebuilt by the previous owner who drove it to Texas & back to Tennessee. The motor has about 28,000 miles on it. I don't know what else to check.
Knoks can be dificult. the rocker arms can cause a Knock. The two times I ran into this it was because the rocker was actually so loose that it wasn't taping but knocking. Next is colapsed piston skirt. Dodges don't do this as some older blue oval stuff but it can happen. The only way to track this is to pull it apart and start doing some very carefull measurements. Bottom end: Knocks can come from both rod big and small ends as well as mains. It sounds like you had the pan off already. I prefer to measure clearances with "Plasti-guage" but many times I found the problem by pusing and pulling the rods. If you can feel movment its bad. The average person can feel about.007 movement. Your engine probably allows.003 max spec. (check that as I didn't) so if you feel the rod move toward the pisto or away this is the problem. Piston pin knocks are tougher, and quite rare, The engine needs a tear down and carefulll measurment to find this. If the problem doesn't show as a rod check the mains carefully and the ens play on the crank. And finally the weird one, are you sure the flex plate isn't cracked and that all the tourque converter bolts are tight. Did a complete tear down once before I found that. Good Luck
Thank you so much for your response. I will check all this out. I haven't pulled the valve covers yet but I will next weekend. Seems weird that it was running fine & the knock just appeared. Sounds like it coming from the passenger side but then it sounds like from under the carb. I'm hoping its just a rocker arm.
Jerry
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