Knocking noise, seems different from others
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02-17-2019, 09:22 PM
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Knocking noise, seems different from others
My 300 six is running pretty well since new lifters. Oilpressure has gone up too, though I'm also running heavier oil than before (Shell Rotella 15W40) - at least 19psi hot idle, 25-40 driving around. However, there's a knocking sound that doesn't quite match any I've read about. It's a medium-light knock like a diesel, only happens under light load - but not no load - and medium or higher RPM. With no (external) load or high load, or at idle, it's absent, which makes the pull-plug-wires-til-it's-isolated test impossible (I suppose I *could* drive it a few times on five cylinders, but I'm concerned about gas washing the rings). It may be absent when cold, but certainly more present when warmed up.
Furthermore, there's another knock that may or may not be the same. That one is occasional or very intermittent, does happen at idle, and seems to go away with the clutch in. It also is quieter or absent when cold.
Main bearings are louder and deeper. Connecting rods seem to be worst at startup. Wrist pins are reported as being present at idle. I'm stumped...
Furthermore, there's another knock that may or may not be the same. That one is occasional or very intermittent, does happen at idle, and seems to go away with the clutch in. It also is quieter or absent when cold.
Main bearings are louder and deeper. Connecting rods seem to be worst at startup. Wrist pins are reported as being present at idle. I'm stumped...
#2
02-18-2019, 02:05 PM
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02-19-2019, 10:39 AM
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02-19-2019, 05:54 PM
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#6
02-20-2019, 12:51 PM
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I hate to speak for others, and please correct me if I'm wrong @mark1986F150 or @78Fords ...
But the way I read it, Mark was strictly referring to base timing - adjusted by rotating the distributor body.
78Fords, on the other hand, was referring to reducing vacuum advance, and not base timing. Since your vacuum basically drops off at WOT, it seems logical that this might help your situation at light load / low throttle. By the way, is your distributor connected to ported or manifold vacuum? I'm guessing ported...
If you disconnect the vacuum advance completely, and take it for a drive (with the ports capped), does the knocking go away? Might be a quick way to verify the vacuum advance as the culprit?
But the way I read it, Mark was strictly referring to base timing - adjusted by rotating the distributor body.
78Fords, on the other hand, was referring to reducing vacuum advance, and not base timing. Since your vacuum basically drops off at WOT, it seems logical that this might help your situation at light load / low throttle. By the way, is your distributor connected to ported or manifold vacuum? I'm guessing ported...
If you disconnect the vacuum advance completely, and take it for a drive (with the ports capped), does the knocking go away? Might be a quick way to verify the vacuum advance as the culprit?
#7
02-20-2019, 01:05 PM
I hate to speak for others, and please correct me if I'm wrong @mark1986F150 or @78Fords ...
But the way I read it, Mark was strictly referring to base timing - adjusted by rotating the distributor body.
But the way I read it, Mark was strictly referring to base timing - adjusted by rotating the distributor body.
Sounds like it's carbed though. Agree with your suggestion to disconnect vacuum advance (and plug vac nipple on carb) and take it for a test drive. If the vac advance is too aggressive, it could cause knocking at low / no load & high RPM, but it wouldn't necessarily ping at WOT because vac advance is not active then.
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#8
02-20-2019, 05:09 PM
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#9
02-22-2019, 11:17 AM
78Fords, on the other hand, was referring to reducing vacuum advance, and not base timing. Since your vacuum basically drops off at WOT, it seems logical that this might help your situation at light load / low throttle. By the way, is your distributor connected to ported or manifold vacuum? I'm guessing ported...
couple months back i had to get a new timing ignition module because it would cause it to idle rough and bogg on acceleration. when i replaced it i had a light ticking tapping at just light throttle, so i backed of the timing curve and that fixed it, make sure you see if your vacuum advance is ported or full vacuum, this will change the amount f adjustment you need. best of luck to yah.
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gatesj
Ford Inline Six, 200, 250, 4.9L / 300
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