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| Knocking, loose rocker arms https://slantsix.org/forum/viewtopic.php?t=22274 |
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| Author: | Big John Hamhock [ Thu Mar 15, 2007 2:39 pm ] |
| Post subject: | Knocking, loose rocker arms |
I have a pair of '65 Darts, one's a fixer, the other a parts car. The fixer has developed a knock. It was only noticeable when at highway speeds a while ago, now it's noticeable at lower speeds. I had the valve cover off the other day and noticed that I could wiggle a few of the rocker arms back and forth and figured that must me what the problem was. I figured I'd swap out the whole rocker shaft from the part-dart, since it hadn't had the knock when last I drove it. But when I took off the valve cover on the part-dart's engine, I noticed the same thing: a few of the rocker arms wiggled freely from side to side on the shaft. Is that normal or indicative of a problem? What should I do first? I know it's a pretty shade-tree question, but I'm a pretty shade-tree guy who's learning, so any help would be appreciated. |
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| Author: | dakight [ Thu Mar 15, 2007 3:06 pm ] |
| Post subject: | |
What you're describing is entirely normal operation unless the clearance is excessive. All the rockers over closed valves will move freely up to the amount of valve lash which is .010 on the intakes and ,020 on the exhaust. They can also move back and forth along the shaft between adjacent rockers / spacers. A little lifter rattle is normal at idle, especially with a cold engine but if the noise you're hearing can be described as a knock I think I would look somewhere else to find its source. |
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| Author: | Big John Hamhock [ Thu Mar 15, 2007 3:14 pm ] |
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A buddy just told me I should try adjusting the valves, in case the clearance is excessive. If that doesn't cure the problem, where should I look next? Also, how would you define the difference between a knock and a rattle? If it helps, it's making the same sound it once made when I (stupidly, oops) let the oil get two quarts low. Adding oil took care of the problem then, but now it constantly makes the same sound at about 45mph. |
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| Author: | dakight [ Thu Mar 15, 2007 3:25 pm ] |
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valve lifter rattle is sort of akin to heavy rain on a tin roof. A knock is more of a heavy rapping noise like a hammer hitting something repeatedly. If you let the oil run low and heard a knock at that time it's entirely possible that one or more bearing were damaged and it is just now coming back to haunt you. One trick I use to locate the source of sounds is to use a short length of broomstick or thick dowell; place it against the engine in different place and list for the sound. Where you hear it the loudest is likely to be the problem area. You can do the same thing with a length of rubber hose too but that works better with external sounds like bearings and frayed belts. |
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| Author: | SlantSixDan [ Thu Mar 15, 2007 4:06 pm ] |
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This is normal. There's some lateral play in the rockers on the shaft. It's not causing your knocking. What sort of a knock have you got? Is it a deep "Thunk!Thunk!Thunk!" or is it lighter in timbre? Could be caused by a lot of different things, from worn-out rod bearings to a faulty fuel pump or a clogged oil pickup screen. Does your oil pressure warning light work (i.e., does it come on when you first go to start the engine)? Does it come on when the engine knocks? |
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| Author: | Ron Parker [ Thu Mar 15, 2007 4:43 pm ] |
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Also if it a automatic could be the famous flexplate to converter bolt or bolts backing out . sounds like a rod knock. It has happened to me three times once on my 340 engine and twice in my slant race car.Thanks Ron Parker  Bagels On Juice Im Bamboozled |
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