: 1969 Deville - Exhaust whistle sound - acceleration



69Chateau
06-07-11, 12:42 PM
Under heavier acceleration and when the engine is working harder to climb up a hill, I get a high-pitched whistle sound out the tailpipe. I can also recreate it by just revving the engine with the car in Park as well.

I'm suspecting muffler or resonator? Anyone experience this or confirm or deny my suspicions?

jcolliga40
06-07-11, 01:28 PM
Dude that's your Turbo you didn't know. LOL

outsider
06-07-11, 02:32 PM
Yeah turbo! the whistle goes WOO WOO :D

it sounds to me like something is restricting the exhaust just enough to cause the whistle sound.

69Chateau
06-07-11, 03:35 PM
I'm sure people pay good money for the turbo whistle sound, just not me.... And not on a '69 472!

If you think its some kind of restriction, could replacing the muffler and resonator be my best bet? Come to think of it, perhaps its a good opportunity to add a new exhaust system that's quiet during highway operation, but still provides an authoritative sound during acceleration to remind you (mainly others) there's a 472 under the hood!

Uh-oh! I'm starting to sound like the 1969 Cadillac ad campaign! "See your Cadillac dealer and experience a Command Performance Drive."

isotop14
06-10-11, 08:42 AM
I will go crazy!!!
I have the same problem,,, on my 1969 Deville Coupe 472!!!

I have installed a new carburator, new water pump,,,
I have removed the header riser, removed the exhaust system...

In my opinion it its a problem with the output valves in the cylinder heads (the valves dont open enough)
because I have removed or renewed all other part outside the bigblock


Stefan from Berlin Germany

69Chateau
06-10-11, 11:42 AM
Exhaust valve leak... Never thought of that. I hope that's not what it is!!

cadillac_al
06-11-11, 06:51 AM
If the exhaust is free flowing then it is probably a burned out/eroded valve. It could also not be seating completely from too much carbon deposits. Now that I think of it, I have seen valves stick after a car has sat for a long time. Those sticky valves will come out of it eventually. A little snake oil might help it along as much as I hate to admit it. I think those sticky valve potions are just kerosene anyway.

Fleetwood70
06-12-11, 04:10 AM
Check to see if the baffle in the secondary side of carb is present. When I forgot to put mine back in the carb after rebuild, when revving it made whistling sound when secondaries were opening.

tqwrench
06-12-11, 09:47 PM
All kidding aside, there are exhaust whistlers for sale out there, we put one in a co-workers truck and it drove him nuts for a week before it finally fell out. Make sure you don't have any pranksters running around with mischief on their minds.

Aside from that, the baffle is a possibility on the carb. I had a 70 Fleetwood and remember that being there during a rebuild. It's primary purpose is improved tip in feel on heavy acceleration.

Other possibilites among restrictions are the double-wall exhaust pipes that were used at one point, I'm not sure which manufacturer came up with that bright idea, but the inner wall could deteriorate and start to collapse on itself. I think that's fairly rare. Another co-worker of mine had to work on a '70 that wouldn't make any power. He took it out and held it flat to the floor down the road till he heard a loud bang and the car took off like a demon. A family of rodents camped out in the muffler somehow. I don't think there was enough left to positively identify the species after that road test. It blew the muffler apart.

Also, if it's a 69, I believe they used A.I.R., at least in CA. Is something going on with the plumbing to the heads? Does it have an AIR pump?

69Chateau
06-13-11, 10:21 AM
Yes, it has a A.I.R pump...

69Chateau
06-13-11, 12:08 PM
Perhaps I'll start by going around the engine and do a dry compression test on each cylinder to see what happens. If I find one that's way off, I might hook up an air source and listen via stethescope to the tailpipe and see if I've uncovered something.

How does that process sound?

CADforce69
06-13-11, 03:09 PM
In good logic, if the problem comes from a valve leak, compression should be lower in the affected cylinder and you should be able to locate whistling sound there. If it was my car I would rather prefer it came from the carb baffle but if you didnīt touched your carb, itīs unlikely. Good luck!

69Chateau
06-14-11, 01:54 PM
Question: If its one particular exhaust valve leaking, wouldn't the "whistle" have a rhythmic pattern to it that would coincide with the compression and exhaust stroke within the affected cylinder? More of a fluttering whistle? The whistling I'm hearing is a constant whistling sound that has no discernible pattern to it.

Just thinking out loud here... (And hoping a valve leak as nothing to do with this!)

outsider
06-14-11, 02:19 PM
could it be your uh...forget what it's called. It's a butterfly type thing that is spring loaded where your passenger side exhaust manifold meets the exhaust pipe. It's purpose is to help the engine warm up faster and is supposed to be open when the engine warms. Maybe it's not opening all the way and that is causing the whistle?

CADforce69
06-14-11, 07:06 PM
Good thinking, outsider. Itīs something to check; the problem is that you have to unscrew exhaust manifold and some of the bolts use to be stuck and tend to break when they are forced.

CADforce69
06-14-11, 07:11 PM
Question: If its one particular exhaust valve leaking, wouldn't the "whistle" have a rhythmic pattern to it that would coincide with the compression and exhaust stroke within the affected cylinder? More of a fluttering whistle? The whistling I'm hearing is a constant whistling sound that has no discernible pattern to it.

Just thinking out loud here... (And hoping a valve leak as nothing to do with this!)


If it happens under heavier acceleration the engine is supposed to be revving at => 3.000 RPM I think at that engine speed fluttering would not be noticed.

cadillac_al
06-14-11, 07:22 PM
Question: If its one particular exhaust valve leaking, wouldn't the "whistle" have a rhythmic pattern to it that would coincide with the compression and exhaust stroke within the affected cylinder? More of a fluttering whistle? The whistling I'm hearing is a constant whistling sound that has no discernible pattern to it.

Just thinking out loud here... (And hoping a valve leak as nothing to do with this!)

That's an important detail. A bad valve would have a rythem to it. When I completely burnt a valve It was a loud tick that echoed down the exhaust pipe. That exhaust flapper is a good thing to check as was mentioned.

69Chateau
06-15-11, 01:45 PM
The 'Heat Riser Valve' I think is the name for that butterfly thing in the passenger side exhaust manifold. I'll look in the shop manual because I don't know if my car has one or how it works.

outsider
06-15-11, 02:16 PM
If it's a 69 then it should. My 69 shop manual says it's on all models.

69Chateau
06-15-11, 02:33 PM
I will check it out... If I don't have to take the exhaust manifold off to remove/inspect!

I'm hopeful that I'll be able to play around with the car tonight. Do a compression test, crawl underneath and look at this heat riser valve, beat on the muffler and resonator with a rubber mallet, etc... So I should have some updates tomorrow.

outsider
06-15-11, 03:04 PM
Nice. For the record, I didn't have to unbolt the exhaust manifold from the engine to get to my heat riser valve. It is a separate piece that bolts in between the manifold and the pipe. Mine is broken so I just pulled out the middle part and just put the casing back in place to bridge the gap between manifold and pipe.

tqwrench
06-15-11, 09:21 PM
That's the heat riser, later models were vacuum controlled, this one is operated much like a choke coil. That is a good one to check. It closes one side of the exhaust off and forces it through the intake to the other exhaust manifold. It heats the intake to keep fuel from condensing on the intake runners when the engine is cold.

isotop14
06-16-11, 07:59 AM
to outsider,
that thing is called HEADER RISER...
I have the same problem and I have removed the header riser flap totally... there is NO improvement

69Chateau
06-16-11, 10:50 AM
Checked compression last night. That's about all I got too.

Results: Cylinder #1 = 180 psi, #3 - 181 psi, #5 - 181, #7 - 178, #2 - 192, #4 - 179, #6 - 185, #8 - 181

So it doesn't appear to have any major leaking issues (phew!).... Now I think I need to go after exhaust items downstream from the block. Looking through the shop manual, it appears they call that butterfly in the passenger side exhaust the 'Manifold Heat Control Valve'. I'm going to start there and work my way back.

outsider
06-16-11, 11:20 AM
glad to hear the compression test came out good!

69Chateau
06-16-11, 01:47 PM
isotop14 was alluding to the valves not opening far enough. I suppose that could still be an issue totally independent of the compression test results. I'm assuming cam lobe wear would cause the valves to longer open as far? Are the rocker arms adjustable on these cars?

69Chateau
07-12-11, 05:08 PM
Check to see if the baffle in the secondary side of carb is present. When I forgot to put mine back in the carb after rebuild, when revving it made whistling sound when secondaries were opening.

Was the whistling sound out the exhaust or near the carb?

DouglasJRizzo
07-12-11, 06:41 PM
My experience with my 68 Sedan De Ville was an exhaust pipe that was collapsing internally partially blocking the flow - car would idle ok but couldn't accelerate properly and made a wheezing and whistling sound. When we cut the pipes out, on of them was collapsed and it looked like the muffler was beginning to do the same.

Fleetwood70
07-12-11, 10:37 PM
Was the whistling sound out the exhaust or near the carb?
Oh, nevermind, It was definitely carb whistling. But, maybe the whistling sound could travel through engine and to the tailpipe? I don't know, lol. I didn't drive it, just revved it in park, didn't listen to exhaust sound at the time.