All Big Six PCV and turbo waste gate sound...

Relates to all big sixes

F-250 Restorer

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So, I have a fascinating and perplexing problem/noise. When I shift from 2nd to 3rd (on zf trans I use 2nd as 1st due to granny 1st) there is noise that sounds like a turbo wastegate. Sometimes I can barely hear it when shifting from 3rd to 4th. It began when I built a new exhaust system: Clifford shorty headers to dual 2.25" for 6' into a single 2.5" in and out FM.

I checked and checked for loose brackets, bolts, etc. I even suspected the Summit brand block to trans spacer. Yesterday I pulled the PCV valve b/c there was oil on the v. hose. When I drove without the pcv in place, the noise vanished. I replaced with a new one. Noise returned. I reduced the v. line from 3/8" id to 1/4" id and there was a noticeable reduction in noise volume.

Can someone explain what is happening? Thx.
 

F-250 Restorer

Famous Member
I guess it does sound to weird or crazy to get a response. I guess I should say that the noise sounds like a momentary buzz, "Vvvvvvv."
 

pmuller9

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When you shift from 2nd to 3rd the engine rpm is high and the throttle plate is suddenly closed causing a high intake manifold vacuum.
Can you duplicate the sound by revving the engine and letting the throttle snap closed?
 

F-250 Restorer

Famous Member
pmuller9: Thanks for the reply. I started a process of going through the engine, drive-line, etc., and checking to make sure all was tight. I found my header stud nuts were loose. Once I tightened them, the noise was no more. This engine/exhaust/trans combo has always made a vvvvver sound when I let off the gas to shift, but that is clearly in the exhaust now, and much quieter. Thx for all the help you're given in the past.
 
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