I was cruising along about 5 miles away from home and I start to hear a disgusting knock. At first thought I say I must have cleaned out a bearing but I don't know. I changed the oil and saw no glitter or shavings (check one). Pulled the vc's to see if it was possibly a bent push rod or roller rocker out of wack....nope (check two). Listened for the noise with a scope all around the motor and the sound is very hard to pin point. If I put my ear to the intake I hear it the loudest and to the back of the motor around the bell housing I hear it the loudest. The last check I did was pull each plug wire while the car was running to see if I could get the knock to change a note. NO MAS! What could my knock be?
Riddle Me This Knock
- Thread starter elarm1
- Start date
I chased a distinguishable knock around for a couple of days last summer and it turned out of all things to be a loose plug wire. Put it back on and the knock was gone.
Have you made any changes to the car recently that could contribute to the noise?
Have you made any changes to the car recently that could contribute to the noise?
I thought of the lifter but after running the engine with the vc's off, I couldn't distinguish if if could be that. Clutch pushed in or out, the noise is still there. I haven't made any changes to the motor at all. I initially thought it was an out of adjustment roller rocker but I set them to specs and I have the same noise. The car runs fine other than the knock. Oil pressure on my guage is above 50 at start up and hangs around 40-45 when its running.
Gotta give us some more info man.
Does it knock all the time, or only during cold start?
Does the knock get quieter as the engine warms up?
Is the knock in sync with engine RPM,
Does this happen when driving, or sitting at idle, or both
Have you made any other mods to the car (not just engine mods) that could contribute to the noise? For example, a new clutch and flywheel could be making slight contact with the bell housing, creating the sound you hear.
No chance said "knock" is some fort of exhaust leak? A header leak can sometimes fool ya.
Does it knock all the time, or only during cold start?
Does the knock get quieter as the engine warms up?
Is the knock in sync with engine RPM,
Does this happen when driving, or sitting at idle, or both
Have you made any other mods to the car (not just engine mods) that could contribute to the noise? For example, a new clutch and flywheel could be making slight contact with the bell housing, creating the sound you hear.
No chance said "knock" is some fort of exhaust leak? A header leak can sometimes fool ya.
The knock is there all the time and is in sync with the rpms. It's there all the time at idle or driving. My next move is to disconnect the transmission to see if I see anything wrong. This knock reminds me of a rod bearing or maybe even something coming into contact with something. The sound is more at the back of the motor which makes me want to drop the trans but it could just be sound resonating
Did you check your plug wires to see if they're all on tight, and/or in good shape? And arking, or loose plug wire can sound like engine knock.
Possible loose flywheel? I've seen this more than once and it is hard to differentiate from a rod knock
The flywheel being loose reminded me of an event some years ago. In my case the knock was from the flywheel, not because the bolts were loose but rather because it cracked between the mounting bolts. When the bolts were removed the flywheel came out in two pieces.
modulistic
Active Member
- Nov 26, 2002
- 383
- 30
- 29
i rebuilt a chevy 350 with a bad knock. it was strange as hell because all the bearings looked great. when one of the pistons came out, a piston ring was broken and fell out in two pieces.
This is what I'm thinking but I won't know until I tear her down but this
View: https://www.youtube.com/watch?v=vNVUMx_rJWA
is what I am hearing
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