What would cause the intake manifold to whine?

[jimtash]

This intake has been on two different engines and it produces the same results. A loud whine from the runner areas. Not a vacuum leak whine but an internal harmonics whine. I've had it apart before and nothing looked out of the ordinary. It's merely an annoyance and doesn't seem to hurt performance but if there's a cure to it, I'm up for suggestions.

 

[zblackbeast]

Where exactly do yo here the whine... air tends to whistle not whine. Spray some starting fluid around the area if it revs up its a auum leak.. when was the intake last cleaned? Do you still have the horns installed? Maybe a video?

 

[msteiny]

On the surge tank cross over tube. How do the couplers look on the inside. Have they been cut out or are they still original? Running BBB's?

 

[jimtash]

Everything is factory. Cleaned it about a year ago to figure out if it was the cause of the noise. The horns are there, the couplers look good. The noise is coming from the center where the runners connect to the head. Especially near the surge tank crossover tube. Nothing wrong with the engine.

 

[jelloslug]

Unhook the vacuum like to the secondaries and see if the noise changes. There could be something up with an actuator.

 

[jimtash]

Already tried it. Have a spare intake that I'm going to use as soon as I clean it up and put it back together.

 

[msteiny]

Does the whine change with rpm? If its on that end of the engine it could be the timing belt or the teeth on one of the cam gears. **** it could be almost anything under the timing cover resonating up through the water pump area in the valley. A bearing going bad on one of the pulleys perhaps.

 

[jimtash]

Tried everything. The engine it's currently on is brand new with about 1 mile on it.

On the other engine I loosened belts, took the timing cover off, everything that had to do with the belts was looked at and nothing changed. It's making the same exact sound on this engine it did with the other. It's especially apparent as it comes back down to idle and it does rise with RPMs. Oddly enough though it seems to disappear when the fan comes on. Maybe it's just the fan drowning it out? The noise is loudest in the valley area around the runners towards the crossover tube. Unless something is too tight in the valve train, which isn't the case, the only thing in common with the noise is the intake. Something is messing up the harmonics in it. I can actually feel the whine in it. Like the air is being blocked or having a hard time reaching the last two cylinders in the intake stream.

 

[jimtash]

Here's a video of it:

http://www.youtube.com/watch?v=6loMFculXIQ&feature=youtu.be

 

[RichieSHO34]

If the engine is brand new I would just drive it for a little and see if anything changes, that stuff is still all tight and not broken in.

 

[mrecoolgar]

Could be an accessory such as the Ps pump, Ac comp, Alt...
Bearings could be bad causing harmonics that appear to be coming from the intake.

 

[88GTA92SHO]

sounds like a way to tight timming belt

 

[jimtash]

sounds like a way to tight timming belt

Done as per the instructions in the manual. Rotated the assembly twice and then tightened the tensioner bolt when the yellow timing mark on the pulley was at 0.

 

[JRA2000TL]

My 89 has a whine sometimes when the engine revs; I was also told the timing belt was too tight. Gotta be something in the accessory drive if it's not the timing belt. Does not affect the car's performance at all.

 

[jimtash]

My 89 has a whine sometimes when the engine revs; I was also told the timing belt was too tight. Gotta be something in the accessory drive if it's not the timing belt. Does not affect the car's performance at all.

I just loosened the timing belt tensioner and let the engine run. No change.

 

[jimtash]

My 89 has a whine sometimes when the engine revs; I was also told the timing belt was too tight. Gotta be something in the accessory drive if it's not the timing belt. Does not affect the car's performance at all.

You were right. It's the tensioner spring putting too much force on the belt. I manually went and adjusted it back incrementally (with the yellow mark at 0) and the whine disappeared. Makes a different noise but I believe that's the slack in the belt itself that cannot be adjusted out due to it being overtightened. It should go away if I ever get around to replacing the belt.