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I have a 1987 chevy r10 when the pickup is setting at idle it runs good but when you are driving the truck as a knock like the lifter are rattling what is causing this and why
There can be many reasons . One the rod bearings are knocking when loaded and will soon be knocking all the time as they wear more.Could be a hydraulic lifter that’s going solid. not quit there yet but wont be long. could also be the rocker arms on the valves are beginning to wear. Could be something simple like carbon knock . A piece of carbon has come loose in a cylinder head and is making the knock. Hope this gives you some things to look for and good luck with your fix
