LS7 Intake "Hiss"

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Dec 2, 2006 | 05:26 PM

mikey

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From: Reading, PA

LS7 Intake "Hiss"

Hey guys, we just finished up a 427 LS2 with GM LS7 heads and intake. We hear an audible hiss on the right side or so it seams. The fuel trims look to be ok and we sprayed the area with no change. Has anyone else heard this noise? Sounds like a vacume leak but doesn't act like one.

Mike

Dec 2, 2006 | 07:05 PM

99Fbody99

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Remove the PVC hose and cap it, see if its gone. I use ls6 style valve in all installs now.

Dave

Dec 2, 2006 | 07:07 PM

mikey

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From: Reading, PA

This has an LS2 style valley cover and does not use a PCV. We did disconnect and cap it with no change. The hiss seems to be coming from between the #6 and #8 injector but it's so hard to tell really.

Dec 3, 2006 | 10:58 AM

Louis

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Mikey, all of the C6Z stuff is quiet as can be. Perhaps it is on the underside of the port?

Dec 3, 2006 | 11:34 AM

Nate_Taufer

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Mikey, I have had this same problem on my car for quite a while. I suspect it to be a leaking manifold on the bottom of the intake/runner transition but I'm too lazy to fix it because it still runs fine. I would take the manifold off and look for any casting inconsistencies around the passenger side ports. Maybe you have a torn gasket? Hope this helps and good luck.

Nate

Dec 3, 2006 | 05:06 PM

mikey

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I took the manifold off today and can't see anything wrong. I'm sending it back to the dealer on exchange. Playing the probability game to see if another one does the same thing.