4.6 DOHC Noise

For anything machine shop / speed shop or engine specific. More technical than the range but not quite tuning specific.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

4.6 DOHC Noise

Unread post by bad86capri »

I have a 03 mach 1 with 97 mark viii short block thats fresh built, 04 aviator heads, longtube headers, everything else is stock. The engine has about 15 miles on it now and has developed a whistling/ high pitch type noise from behind the engine after the first couple of miles. The noise is intermittent and goes away while driving and does not change with engine speed. After you shut down the engine it sounds like its bleeding off. Ill post a video. Has anybody experienced this before on these engines?
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 4.6 DOHC Noise

Unread post by bad86capri »

Well it will not let me post a video.
PaulC-turbo5.0
Posts: 104
Joined: 2021 Feb 15, 21:56
Location: Lancaster New York
Vehicle Information: 1989 fox GT convertible
5.0 stock block, E7 heads, stock cam
Explorer GT40 intake flipped to driver side inlet
Single 67mm On3 BB turbo
Flipped JBA headers, custom SS 2.5" hotside built by me
custom 3" coldside thru On3 intercooler
tuning with Moates QH + TPRT
Dechipa's GUFX and supporting files, couldnt have tuned it myself without him!

Re: 4.6 DOHC Noise

Unread post by PaulC-turbo5.0 »

my guess would be pcv system. on my turbo fox, much different pcv setup being turbo, I run it the way Decipha recommends and when I had the system mostly sealed up it would create an odd whistle shortly after starting, which would then go away, but on shut down it would bleed off and whistle like you're describing. I couldnt stand it so and couldnt figure out where it was coming from so I popped a few tiny holes in the line to the oil filler neck which thankfully made it stop.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 4.6 DOHC Noise

Unread post by bad86capri »

Ill check the pcv system. On my setup its basically a standard pcv valve feeding into the big port on the mach 1 intake and the other valve cover has a rubber hose going to the intake tube. How does decipha recommend to run it?
mnorman1964
Posts: 32
Joined: 2021 Feb 17, 23:02
Location: Salem, VA
Vehicle Information: 1969 ford f100 with 2002 5.4L Lincoln Navigator engine twin turbochargers 4R100 trans siemens 80lb injectors, MQAIO

Re: 4.6 DOHC Noise

Unread post by mnorman1964 »

I had PVC related whistling at idle issues as well. Strange sound. Pull PVC hose and noise goes away. still have not figured out the exact root cause. Probably gasket somewhere with a tiny leak.
PaulC-turbo5.0
Posts: 104
Joined: 2021 Feb 15, 21:56
Location: Lancaster New York
Vehicle Information: 1989 fox GT convertible
5.0 stock block, E7 heads, stock cam
Explorer GT40 intake flipped to driver side inlet
Single 67mm On3 BB turbo
Flipped JBA headers, custom SS 2.5" hotside built by me
custom 3" coldside thru On3 intercooler
tuning with Moates QH + TPRT
Dechipa's GUFX and supporting files, couldnt have tuned it myself without him!

Re: 4.6 DOHC Noise

Unread post by PaulC-turbo5.0 »

You should run yours stock being N/A. The Decipha way I mentioned is specifically for boost. I think the details are in the getting started write up.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 4.6 DOHC Noise

Unread post by bad86capri »

I havent had a chance to verify but i think my issue is the idle air control.
decipha
Posts: 4950
Joined: 2021 Feb 15, 12:23
Location: Metairie, LA
Vehicle Information: Work Truck
'19 F-150 3.3L

Re: 4.6 DOHC Noise

Unread post by decipha »

Yeah the idle air control valve can induce a whistling noise as well as some intakes.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 4.6 DOHC Noise

Unread post by bad86capri »

Well im pretty sure my issue was having the wrong spark plugs. I reused the Mark viii plugs because they were new. After thinking about it for awhile it donned on me that the B heads are 4 thread and my C heads are 9 thread. So i changed the plugs and discovered half of the plug was not in the cylinder and the plug was seated on the end of the threads instead of the tapered seat. After changing the plugs the car idle way better and the noise is no longer there.
bad86capri
Posts: 163
Joined: 2021 Feb 16, 10:09
Location: Knoxville, TN
Vehicle Information: 1986 Capri 306, Twisted Wedge heads, RPM II Intake, Anderson B3 cam, 80Lbs Siemens Injectors, MAC Longtube Headers, G-Force T5, Spec 6 Puck Clutch, Ford Racing Aluminum Driveshaft.

Re: 4.6 DOHC Noise

Unread post by bad86capri »

See pics.
Attachments
Screenshot_20221214_095727_Photos.jpg
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