The Dreaded 308 Exhaust Whistle

the sealing material between the "mesh part" and the "wall" of the exhaust tip desintegrates -
the flow of the exhaust gas passing through this mesh sounds like a whistle that is getting worse when revving up

happens over time due to heat and vibration - not a question of if but when ...
easy to cure

 

The permanent fix is relatively easy. You just have to pull off the air injectors from the block just above the exhaust outlet (see picture below), and replace the injectors with a plug. On my former 308 GTS, I got them from Scott, IIRC, one of the members on here. Check the older threads on air injector plugs and you find info on them. You need a plug that has an extension on it to fill the hole, otherwise you'll still get the whistling.
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Glad you were able to fix the whistle, it's an annoying sound for sure. unfortunately the air injection is a time bomb waiting to happen, keep an eye on the injectors and inspect them at service intervals, those injectors have a nasty habit of falling apart and into the valves. Then it's no longer a simple nor cheap fix.

 

Brian,

It's time as much as miles. That picture above is from a '78 GTS with 32K miles on it. When I pulled them out, they were not in as good shape as they appear in that picture. And you can see clearly where they sit in relation to the exhaust valves.

 

It's easy to test for the exhaust tip whistle -
Hit home depot for some flexible steel. I used heating duct tube. Cut two, curl it, then stuff it into the exhaust tips. Whistle still there? try moving the metal tubes to the other side of the exhaust. Whistle still there? Try Steve's tip above.

Mine was simply the exhaust tip issue.

 

Cut slices in the exhaust tips

 

Next time you do a run of the plugs, let me know. I have a slight redesign idea.

 

it'll be awhile as I have easily 20 sets still. what was the idea? couple yrs back the idea floated for a longer nipple, that works for the guys would be doing the job with the manifolds out or engine out otherwise the majority are done in-situ and port matching the protrusion would be difficult. early on it was an idea but didn't pan out, in reality the wave dynamics are not altered enough by the slight dimple vs original stem in the port.

 

That was my idea. I was thinking of installing the plug, spraying a little paint at the exposed nipple end, then removing the plug and grinding the painted edge off. The theory being it would leave a flat surface. Just have to do one at a time to get the pitch back to the correct position.

 

indexing can be a pain, not a bad idea though.

 

for removal of the injectors. with proper tune the engine should still pass the tail pipe test without the injectors. visual, well that depends on the shop. however removal of the system and setting the tune of the engine relies on the shop knowing what they are doing. you're near Brian Crall in the bay area, he's the go to guru for keeping these cars in proper tune.

 

Even right down to the yellow paint!

I have posted these pictures before but since my injectors were ruined, I used them to make my own plugs, each one indexed to a unique cylinder.

It's pretty easy to do, and I like the idea that the inside of the exhaust port is now nice and smooth.
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Here's the rest:
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Nice fix Dave! I'll have to see if that kind of detail was paid to my headers when the previous owner removed the air injection system.

 

That is were the idea came from. smg2's plugs are aluminum so they would be easy to cut down.

 

I've been asked to consider sourcing the inserts to fix exhaust tip whistling. Several posts give dimensions of 2.5"x7" or 3"x6" SS sheet rolled around something like a broomstick.
My question is: Which dimension is rolled, ie: how long are the finished inserts 6" or 7" long or 2.5" or 3" long?

BTW, You may have got them from me, I've sold several hundred of these:
http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/221686-does-anyone-know-where-get-set-air-injection-plugs.html

 

Brian -

can you take a listen to my posted sound files here and let me know if this is what your whistle sounds like? Im having a similar problem.

http://www.ferrarichat.com/forum/308-328/456124-engine-makes-chirpy-sound-when-taking-foot-off-gas.html

 

Timely. Mine sounds exactly like a VW Beetle, and it's first on my list of things to fix. One of my exhaust canisters is loose, so I'm pretty sure that's the issue. Are the air injectors also on the injected cars?

Cheers,

George

 

Yes, if your car has or had an air pump then it has the air injectors. The tubing for them is pretty hard to overlook. #43 - tubing just above the exhaust manifold, #48 - air injector
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Thanks!

 

Still looking for an answer.