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Old 06-28-2019, 09:35 PM   #1
Zenwren
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Chevy 350 knocking after change in climate.

I just moved from Wisconsin to Arizona, I had my '69 C10 trailered out by a friend. When I got it off the trailer I naturally took it for a spin. After an easy 8 miles at 45mph or so I noticed a ticking sound at low speeds (probably there at higher rpm but not over the exhaust) I headed straight home and it progressed to a loud clicking/knocking sound, possibly more from the passenger side. I wouldn't quite call it a knock, at least any knock that I've heard before. Maybe detonation? But why? I tried adjusting timing to no avail. Did it get hot? I don't have a temp gauge (yet) I read somewhere that a sticking thermostat can cause a knocking sound when the hot coolant contacts the cold?
Stock 1969 short block with aluminum L98 heads, th350, temp was in the low 90s for the drive. The truck sat for about a month before I got it. No my friend didn't take it out and beat it before he delivered it.
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Old 06-28-2019, 10:22 PM   #2
Dead Parrot
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Re: Chevy 350 knocking after change in climate.

A couple of non-engine internals possibilities:
Freshly developing exhaust leak. When checking, don't forget the intake exhaust crossover.

Dying power steering pump.

If the problem is still there when you do a cold start, probably not an overheat problem.

Have to ask, low oil level?
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Old 06-28-2019, 10:47 PM   #3
Zenwren
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Re: Chevy 350 knocking after change in climate.

Definitely coming from the engine. Your exhaust comment made me think maybe a spark plug rattled loose so I went out and checked them (no luck) but I did start it up now that it's cooled off and it sounds normal again. Coolant and oil are good.
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Old 06-28-2019, 10:54 PM   #4
rsavage
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Re: Chevy 350 knocking after change in climate.

You could check to see if your torque converter to flex plate bolts are coming loose as a shot in the dark.
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Old 07-02-2019, 12:59 PM   #5
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Re: Chevy 350 knocking after change in climate.

Climate change didn't cause whatever is happening.
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Old 07-02-2019, 01:16 PM   #6
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Re: Chevy 350 knocking after change in climate.

Grabbing at straws here...

Is it possible the exhaust system got bumped during the loading/unloading? (to make it rattle or leak)

Does the clicking loudness change with throttle position? (as in is it really spark knock, or a mechanical problem?) See if a tankful of 92 octane makes the bad noise go away.

Is the weather a lot hotter? (Maybe you need 20W50 now?)
[EDIT: I read again and you said it was quiet when it cooled down. That could be an oil viscosity thing if the weather is really hot. What visc are you running?)

AC compressor or wiring failing?

New hearing aid? :-)

I couldn't help myself on that last one.
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Old 07-02-2019, 01:49 PM   #7
Zenwren
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Re: Chevy 350 knocking after change in climate.

Running 10-40 now, do people really run 20-50 in gas engines??
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Old 07-02-2019, 02:34 PM   #8
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Re: Chevy 350 knocking after change in climate.

I run 10-30 in SoCal when its 100 and A/C running. No issues, so I don't think its the oil viscosity causing a problem.
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Old 07-02-2019, 02:57 PM   #9
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Re: Chevy 350 knocking after change in climate.

UPDATE: I got out my handy dandy harbor freight stethoscope and found the noise was loudest at the fuel pump. When I took it out it came out in pieces. Rod looks alright, new pump going in tomorrow morning. Fingers crossed!
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Old 07-02-2019, 03:29 PM   #10
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Re: Chevy 350 knocking after change in climate.

Fyi we run 10-30 here in phoeinx in the old chevy's. At least I do and I've made it to almost 200k on my 98.
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Old 07-02-2019, 05:37 PM   #11
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Re: Chevy 350 knocking after change in climate.

Quote:
Originally Posted by Zenwren View Post
UPDATE: I got out my handy dandy harbor freight stethoscope and found the noise was loudest at the fuel pump. When I took it out it came out in pieces. Rod looks alright, new pump going in tomorrow morning. Fingers crossed!
Nice! I hope that's the root of it.
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Old 07-02-2019, 05:43 PM   #12
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Re: Chevy 350 knocking after change in climate.

Quote:
Originally Posted by Zenwren View Post
Running 10-40 now, do people really run 20-50 in gas engines??
Quick side-bar conversation... I've always pushed my daily drivers well past time for rebuilds. The 20W50 heavy weight oil helps minimize burning and leaking. I even tried in my C10 and it did get rid of a bad noise it was making. Until it warmed up. My problem was that the previous owner/rebuilder accidentally used standard rod bearings on 0.010 under rod journals. It's all rebuilt now with correct clearances. End of tangent. :-)
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