Where's this noise coming from?

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I agree with fuel and timing.
I plugged my headphones into my laptop and listened.
It doesn't sound metallic enough to be heat riser.
Sounds more like spark knock.
 
I go from where I live to Phoenix on occasion which is a 2,000 foot drop in elevation and I have to pull my timing back a little when I do, or I have detonation under a load.
 
Sounds like knocking due to too much timing advance to me, though piston slap or a bad lifter/rocker could sound like this too. Check the total advance on the timing and retard it anyway (even if it isn't too advanced) just to test the theory. If the sound is still present, take off the oil fill cap and the PVC valve - hold a small rubber hose in one ear and place the other end in the valve covers to see if you can detect the noise origin.

Good luck!
 
68gtxman said:
take off the oil fill cap and the PVC valve - hold a small rubber hose in one ear and place the other end in the valve covers to see if you can detect the noise origin.

Good luck!
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ROFL..... sorry, but some vehicles I've worked on,, would fill your ear with yuk.. lol
 
Sounds like the torque converter bolts hitting the transmission inspection plate. My slant did that after hitting a rock and bent the cover. I know it would theoretically do that when not moving, but no noise idling in N, but made noise under load. Maybe the crank shifts axially slightly. My 82 Aries made a similar noise, but it was a torque converter bolt unscrewing and hitting the block. Same deal w/ more noise under load.
 
Been busy moving in all weekend. I haven't had time to do anything car related, but the plus side of that is I can access my tools! I'll break out the timing light when I have more than a couple minutes. :D

I stopped by a local shade tree mechanic on Friday. He and his buddy said it's spark knock and that I should change the wires to correct it. Is that right?
 
genepewl said:
Been busy moving in all weekend. I haven't had time to do anything car related, but the plus side of that is I can access my tools! I'll break out the timing light when I have more than a couple minutes. :D

I stopped by a local shade tree mechanic on Friday. He and his buddy said it's spark knock and that I should change the wires to correct it. Is that right?
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Change the wires to correct spark knock???? That's the craziest thing I've heard in a long time:violent1:. Not saying you don't need new plug wires cause I haven't seen your car but wires aren't going to magically make spark knock go away. Spark knock is caused by either the timing is too far advanced, carb. running lean, engine running real hot, fuel that's too low octane rating. Oh yeah, oil consumption can also make it spark knock. That's about it.
 
I would avoid those shadetree guys. Do they drive Chevys? Bad plug wires will cause missing. Look at the engine on a real dark night. If you see flashes from the plug wires, they are old and leaking charge, so replace them. If the plugs aren't wired right, it can make the engine run funny. Check your firing order.

"Knock" or "pinging" is technically known as "pre-combustion" or "detonation". It is caused by low octane fuel and/or too much spark advance, and is usually worse at high throttle & low rpm like going up a steep hill in 3rd gear at 40 mph, hotter intake air, and higher compression. Most cars since ~1996 have knock sensors, knock module, and computer control of spark timing. Some after-market ECU's can control knock on our engines. If running a traditional distributor and ignition, you avoid knock by setting the timing conservative for worst case and maybe buying premium gas.
 
Finally got around to checking the timing. I adjusted it as per fishy68's instructions and it sounds A LOT better. I drove around town and on the highway and didn't hear that damned noise all day!

It's very strange to me that that noise just became noticeable at a certain stress level, but didn't change with in rate as rpm's increased.

Now to tweak the carb...
 
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