Engine Whistle - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Classics Fan · 06-27-2023, 10:46 AM

1971 Jimmy has original 350 with 120,000 miles, rebuilt at 85,000 miles. A few days ago during warm outside temps it had a loud whistle coming from under the hood at start-up and idle (around 800 RPM). It went away with some throttle but returned when the engine slowed to near idle speed. It didn’t change pitch with acceleration, just faded away. This happened a few times. No unusual sounds at higher engine speeds or cruise. When the weather cooled the whistle went away too. I wasn’t able to get under the hood to check further. Any ideas what could cause this?

06-27-2023, 10:46 AM	#1
Classics Fan Registered User Join Date: Jan 2018 Location: Anacortes. WA Posts: 118	Engine Whistle 1971 Jimmy has original 350 with 120,000 miles, rebuilt at 85,000 miles. A few days ago during warm outside temps it had a loud whistle coming from under the hood at start-up and idle (around 800 RPM). It went away with some throttle but returned when the engine slowed to near idle speed. It didn’t change pitch with acceleration, just faded away. This happened a few times. No unusual sounds at higher engine speeds or cruise. When the weather cooled the whistle went away too. I wasn’t able to get under the hood to check further. Any ideas what could cause this?



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