I have an 87 F-150 with a 300 six. Once the engine warms a little it develops a screaming sound around the back of the intake. The injectors have all been rebuilt and I checked the fuel rail and everything else I could think of. If you can help please do this thing is driving me nuts.

 

Hmmm... sounds like a leak somewhere. When it heats up, it starts leaking. Just a wild guess. May want to get a stethoscope with a probe to locate where the sound is coming from. A length of hose held to your ear would work too.

 

Most likely a vacuum leak. You can check this by spraying carb cleaner around the intake ports. If the idle speed changes, there is a leak.

Caution: The exhaust manifold can cause ignition! Use the spray sparingly.

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