High Pitch intake whistle GONE!

[Chia]

I found a couple of old pictures that might help you out but I don't know how to post them, will try and figure it out later today.

thanks, that would be great. the easiest way to post a pic is to link it from a photobucket type site.

So did you trace the gasket with a slightly smaller inside diameter so that when you cut the humps, they stuck slightly past the gasket? Are we talking 3 mm?

[02-Scape]

thanks, that would be great. the easiest way to post a pic is to link it from a photobucket type site.

So did you trace the gasket with a slightly smaller inside diameter so that when you cut the humps, they stuck slightly past the gasket? Are we talking 3 mm?

Same diameter except for the humps which stick out into the airflow. Start with about 3mm you may have to grind them so that the butterfly valve does not hit them.

[minnmarker]

I found a couple of old pictures that might help you out but I don't know how to post them, will try and figure it out later today.

If you resize the pictures to @ 640 x 480 in any picture editor you can post them right in your reply. No links required.

Please do. I want to get rid of my whistle!

[minnmarker]

02-Scape, did you then have metal on metal on one side of the throttle body to plenum connection or did you sandwich your "bumpy metal gasket" between two gaskets?

[02-Scape]

I ended up putting the spacer on the plenum, then two gaskets (I had ordered one to make the pattern), then the throttle body as I wanted to make sure the butterfly valve cleared the spacer.

[flapjack]

have you guys considered creating some flow disruptions with glue? If could do this with a reasonably easy to remove, organic epoxy/glue to create some small bumps on the butterfly valve or in the throttle body.

If it works, recreate with something like JB Weld. If it doesn't work, scrape it off.

[02-Scape]

Thought of that but if it comes loose it goes right through the motor.

[Ndawg12]

Sounds like a good way to clog an injector.

[minnmarker]

I just ordered the gasket from Marine Parts Express. Part #3849022

http://www.marinepartsexpress.com/cart/index.php?ID=3849022&Go.x=0&Go.y=0

They had it in stock and confirmed that it will fit on the GM 5.7 EFI engine. They did not know if it would cure the whistle but were curious.

02-Scape, is the swap out pretty straight forward? Anything to watch for that's not obvious?

[02-Scape]

I just ordered the gasket from Marine Parts Express. Part #3849022

http://www.marinepartsexpress.com/cart/index.php?ID=3849022&Go.x=0&Go.y=0

They had it in stock and confirmed that it will fit on the GM 5.7 EFI engine. They did not know if it would cure the whistle but were curious.

02-Scape, is the swap out pretty straight forward? Anything to watch for that's not obvious?

Easy as pie, 6 bolts to take off the plenum, 4 bolts to remove the throttle body, remember to unhook the TB sensor. Hardest part is wiggling the air filter in and out (it's pretty tight in my VTX).

[Steve B.]

I wonder what actually causes the whistle?

Steve B.

[minnmarker]

Easy as pie, 6 bolts to take off the plenum, 4 bolts to remove the throttle body, remember to unhook the TB sensor. Hardest part is wiggling the air filter in and out (it's pretty tight in my VTX).

Torque specs?

[Nitrousbird]

I assume you have the old GEN-I SBC and not one of the modern motors.

Good DIY...you'd think this issue would have been resolved long ago.

[minnmarker]

I assume you have the old GEN-I SBC and not one of the modern motors.

Good DIY...you'd think this issue would have been resolved long ago.

It's a 2005 Monsoon 340. I believe it's pretty much the same as current motors except no cats.

[ryguy1188]

I just ordered the gasket from Marine Parts Express. Part #3849022

http://www.marinepartsexpress.com/cart/index.php?ID=3849022&Go.x=0&Go.y=0

They had it in stock and confirmed that it will fit on the GM 5.7 EFI engine. They did not know if it would cure the whistle but were curious.

02-Scape, is the swap out pretty straight forward? Anything to watch for that's not obvious?

Minnmarker, Please let me know how the Volvo gasket works out and if it fixes the whistle. Did you purchase another rubber gasket to sandwich the Volvo plate?

[ryguy1188]

The throttle body is the part that the air filter is attached to, which is bolted to the intake plenum (not trying to be ignorant but just to be clear). If you unbolt the throttle body (4 bolts), you will see that there is a foam gasket that is between it and the intake plenum. If you are careful you can just peal it off (and reuse). Once you have it off you can use it to make a pattern on some sheet metal (I used some that was about twice as thick as tin). This should mimic somewhat the picture I posted in the original post. Once you have done that, then take the newly made spacer and the foam gasket and put them between the throttle body and the intake plenum, bolt it back together, bolt the intake back on and you are in business. Just make sure the 'humps' you make on your spacer are small enough that the butterfly valve on the throttle body does not hit them. Hope this makes sense.

02-Scape, I'm trying to get the right thickness sheet metal. What gauge would you say it is? Is it just thin enough to not bend on it's own weight?

[minnmarker]

Minnmarker, Please let me know how the Volvo gasket works out and if it fixes the whistle. Did you purchase another rubber gasket to sandwich the Volvo plate?

Yes, I'll post up on the install - and results next Spring.

The part is described as a gasket so I assume it will function as a gasket. If it is just a metal plate then I'll probably get 2 gaskets to sandwich it between. It should arrive in a day or two.

[02-Scape]

02-Scape, I'm trying to get the right thickness sheet metal. What gauge would you say it is? Is it just thin enough to not bend on it's own weight?

Yes, my fear was if it was too thin it would vibrate and a piece would break off.

[minnmarker]

Just received the Volvo "gasket."

http://www.marinepartsexpress.com/cart/index.php?ID=3849022&Go.x=0&Go.y=0

It is not a gasket but rather a flat stamped metal piece that has the humps on the inside diameter. It looks very well made.

Since it is not gasket material I am going to get two ACDelco 40-5093 gaskets to put on each side. Air leaks into the intake downstream of the butterfly valve are not good.

[justgary]

... Air leaks into the intake downstream of the butterfly valve are not good.

... and could cause a high-pitched intake squeal. Hey, wait a minute....

[minnmarker]

Went up tot he cabin last this weekend and found the butterfly valve housing has 3 blots. There is one bolt top left that is hidden in picture. Does not look like the standard GM intake manifold or valve housing - no surprise Indmar...

The special gasket (see a couple posts above) is designed for 4 bolts. It looks like the correct inside diameter and the top 2 bolts look like the right spacing and orientation so I'm thinking of trial fitting it in place and seeing what happens. Plan to be very careful with torquing the bolts and doing the bottom one last as it will be "floating."

Anyone got any red flags or, better yet, experience with this? I really want to get rid of the whistle.

[minnmarker]

Still determined to get rid of the whistle so last weekend I thought why not just take the butterfly housing off and see how hard it would be to round off the edges on the butterfly valve - that supposedly cause the whistle.  I did not want to try to do it in place due to access difficulty and the possibility of getting grindings in the wrong place.  I figured the only thing that could go wrong was wrecking the gasket.

Tools needed: 4 mm hex for 1/4 or 3/8 inch socket wrench, T15 driver, Dremmel with fine stone, 400 grit wet/dry sandpaper, shop towel.

Getting it off was easy.  First disconnect the throttle cable from the flat plate on the port side then disconnect the two sensor wires.  Check to make sure everything is free and then take out the (in my case - 2005 Monsoon 340) 3 bolts holding it to the intake plenum.  Came right off but I was careful to watch and make sure the gasket stayed with one surface only.  It did.

Note the two little bumps to the right of the shaft.  Remember how they are oriented and where they go.  Back out the 2 screws with your T15 driver, rotate the shaft so the valve is wide open, and slide the disk out the intake side (facing you in picture).

[minnmarker]

Now take the dremmel and carefully take the burr off the edge of the disk being VERY CAREFUL not to grind anything off the outside diameter of the disk.  Smooth it out with the sandpaper.  I did not want to reduce the total disk area since that would let additional air through when the valve was closed.  That might have caused the problem mentioned above in the post by Fman.

Now clean the disk off and put it back in with the same orientation.  Remember the bumps.  Let the valve close and make sure the disk is centered then put the screws back in and put the housing back on the intake plenum.  Be careful with the gasket.  Total time was only 30 minutes.

I'll let you know in a couple weeks if the whistle is gone.

I still have the bump gasket pictured in my 1/25 post if anyone can use it.  Not worth returning.  The center to center measurements for the bolt holes are 8.4mm x 6.3mm and the ID is 7.9mm.  PM me if you have the 4 bolt housing and are interested.

[minnmarker]

On 3/28/2016 at 10:16 AM, minnmarker said:

Still determined to get rid of the whistle so last weekend I thought why not just take the butterfly housing off and see how hard it would be to round off the edges on the butterfly valve - that supposedly cause the whistle.

It worked!

[MadMan]

By the way, all the butterfly valves I've worked on had the screws "staked" (intentionally deforming the exposed threads) to prevent them from coming loose and being ingested by the engine.

 

I  usually just use some wire cutting pliers to do this.

Edited May 3, 2016 by MadMan