Intake Manifold Crack

[sk8salomon]

For the past 6 months I've been searching for this mysterious whistling noise between 2,000~2,200 RPM. Seems to have started doing it when I replaced the Violet BVSV. https://forum.ih8mud.com/showthread.php?t=156800&highlight=BVSV+Whistle
I've replaced vacuum lines and air pump hoses but haven't been able to locate it. I tore the intake off last night and found this 2" + crack inside the manifold. Could this be where the noise is coming from? Wouldn't the crack cause air/fuel to leak into the exhaust manifold?

 

[sk8salomon]

more pics

 

[FJ40Jim]

No, the crack will not let air/fuel leak into the exhaust. Inside the exh manifold is hot & pressurized, so the exhaust gas is blown through the crack, up into the intake.

I've seen plenty of cracked intakes, and heard plenty of whistlers, but never been able to attribute the whistling to an intake crack. I'm thinking the conditions around the crack, especially on the bottom side, would not be conducive to producing a whistle sound.

Every whistle I've ever fixed has been a leak in an intake manifold gasket.

Just my $.02

 

[sk8salomon]

thanks Jim. I'll try a new gasket!

 

[Dave-T]

Also a lot of times casting marks on aluminum components like manifolds and valve covers can appear as cracks. Make sure the gaskets above and below the carb insulator are good.

 

[DirtyLittleSecret]

I was gonna say, it looks like a casting mark rather than a crack.
Be happy! Just ruled out another part!

 

[Dynosoar]

I don't think that looks like a crack but it is hard to tell without seeing the under side. I am more concerned about the notch around the carb seating area. I would clean that up with a grinder. IH8whistling noise too. I am with Jim C. I bet its a warped manifold or bad intake gasket.

Dynosoar

 

[sk8salomon]

thanks guys. just ordered a new intake gasket. here's a pic of the underside. there is a crack as well, hard to see but this is the best pic i could get.

 

[Dynosoar]

Yep, it's cracked! Take it to a TIG welder and have it zipped up.

Dynosoar

 

[lowtideride]

I have one you can have. pay shipping. Cruiser Love.

 

[sk8salomon]

I have one you can have. pay shipping. Cruiser Love.

thanks lowtide but i just had a guy here at work weld this up. i'll try this one with a new gasket and see if the problem goes away.

 

[DirtyLittleSecret]

Wow. Im impressed at how well that looked like a casting! Deceptive little buggers...
Hope he pre/post heated the material for welding...cause if that weld lets loose inside its gonna travel and cause all sorts of issues.Looks cold to me!

 

[NorCal60]

I have one you can have. pay shipping. Cruiser Love.

If Sk8 doesn't take you up on the offer then I'm interested.

I've gotta replace the manifold gasket anyways.

 

[lowtideride]

Pm me brotha

 

[Live to Ski]

Hey, also make sure your exhaust heat riser spring activated valve works freely.