Whistle at Idle

[rtviper]

At idle the motor has a loud whistle. It idles fine but I have always thought it was assoicated with a vacume leak. I have run the smoke machine 2 times and no leaks anywhere. I have tried the stethascope with no luck. I dont know how you check for leaks from manifold into the engine? It will idle down to several huindred RPM with no issues except for the noticable whistle.
Has anyone continued to run their cars with a whistle with no probs? Its a Hogan manifold. I even tried the brake cleaner spray at all bolts and gaskets. No discovery. Any ideas?
Thanks

 

[bosted86]

What Doghouse Do You Have. I Know Some Have Been Know To Whistle At The Rear Of The Doghouse.

 

[Nick Micale]

My guess it would be the intake?

Have seen a couple intakes that would not seat on the bottom side of the intake and leak into the valley.

One I just finished had a blown head gasket and the heads were freshened and milled 0.010". This was enough to change the angle of the mating surfaces and leak. Thinner gaskets solved that problem.

When this was encountered on another car a few years ago, we made a plate to replace the plenum and it has an air fitting in it. After loosening [or removing] all the rockers to close the valves, air pressure when applied would then blow out the spark plug holes.

Removing the intake in both cases showed the intake gasket was oiled half way up.

On most performance builds when we check intake fitment, we have to mill the intake surfaces and sometimes the end surfaces also. This is especially true with after market intakes.

If that Hogan was not custom fit to your engine and also checked with an angle gauge, good chance of the being the problem.

 

[rtviper]

Thanks guys. I guess it has to come off. I am sure it was fit to the block as everything was new and ordered for this motor by Duttweiler but the build is over 10 years old. With few actual miles but plenty of start ups I am sure a leak has developed on the inside. Was hoping for some indicator to point directly at the area of the leak.
Thanks again.

 

[bison]

At idle the motor has a loud whistle. It idles fine but I have always thought it was assoicated with a vacume leak. I have run the smoke machine 2 times and no leaks anywhere. I have tried the stethascope with no luck. I dont know how you check for leaks from manifold into the engine? It will idle down to several huindred RPM with no issues except for the noticable whistle.
Has anyone continued to run their cars with a whistle with no probs? Its a Hogan manifold. I even tried the brake cleaner spray at all bolts and gaskets. No discovery. Any ideas?
Thanks

Id try the smoke machine again. Ive never seen one of these miss a vacuum leak. Usually the throttle body has a big leak at the shaft seals unless they have been replaced. But i doubt yours is since your proabably not running a 20+ year old stocker.

 

[rtviper]

You are right it is an Edelbrock TB and both times we used the smoke machine long enough the smoke was comming out the exhaust and turbos. But nothing from the engine. Although the build is about 11 years old and has sat for about 9 of the years I am impressed that Duttweiler sealed the motor so well there is not one leak of fluid anywhere.
I was hoping to hear about a test that would indicate it was the intake gasket or ??.
By the way Brian I will ship your TB Friday morning. Thanks

 

[bison]

You are right it is an Edelbrock TB and both times we used the smoke machine long enough the smoke was comming out the exhaust and turbos. But nothing from the engine. Although the build is about 11 years old and has sat for about 9 of the years I am impressed that Duttweiler sealed the motor so well there is not one leak of fluid anywhere.
I was hoping to hear about a test that would indicate it was the intake gasket or ??.
By the way Brian I will ship your TB Friday morning. Thanks

Id try it again with the rocker arms off so the valves are all closed. Just to be sure you didnt miss it. If you find nothing again then id pull the intake and reseal it. Maybe it only leaks when the vacuum reaches a certain level. In that case the smoke wouldnt help.

 

[TweakedOut6]

Before you go through the trouble of pulling the intake off, try using a long piece of heater hose to determine the area of the leak. If you can hear the leak over the sound of the engine running, then it should be easily detectable when you use the heater hose to isolate the whistle.