47-55.1 Exhaust Flex Joint Required?

[b-mac]

Do I need to put some of those flexible joints somewhere in the exhaust?

And also, Russ, if you're out there, where in Wichita should I take the manifolds to have the flange studs replaced? I don't have a torch, and I can't get a few of them out.

[mr48chev]

Well maybe I didn't read that correctly last night. By flexible joints I was thinking the short pieces of flex pipe that my VW Passat has and my Cad DTS has on the exhaust pipes as both are front wheel drive.


The spring loaded ones like Joedoe suggested do a good job of keeping things tight but not so rigid something breaks.

The Muffler shop I go to "Muffler Bandits" in Yakima WA uses the same hangers that Miricalpieco showed and they work well.

[joedoh]

do you have the donut type gasket on your downpipe? those have a spring type exhaust stud and will give a little isolation from vibration.

kevin at american muffler on oliver is the only guy I will use. kevins pricing is all over the map, usually based on what he wants for lunch I think, but I havent ever felt outright overcharged. I used to use bill at the south one, until one day he backed my truck out and ran over a slice of pipe, giving me an instant flat. denied it even though the slice was still laying there and matched the cut in my previously air holding tire. he shut the garage door in my face. I wish mark was still hanging exhaust, we did some crazy stuff.

[MiraclePieCo]

Nice job on the pipes!

Of course your hangers should move freely and have rubber isolators. Kinda like these below. I've had solid mounted exhaust before - man did they creak, crack and pop as they cooled down!

[dsraven]

like said, exhaust needs to flex some but the flexie pipe is more or less for the cradled engines in front wheel drive vehicles where the engine sits sideways and torques up differently than a rear wheel drive vehicle. these styles rotate the rear of the engine upwards under normal torque and if the engine mounts are worn out the flexie pipe is the first to let you know when it tears apart.
springs and donuts on the pipe to stock manifold and insulated rubber hangers down the line should be able to accept the flex in the system from engine torque. if you run headers then they will not have the flex at the engine end because they have a different header to pipe mount than a stock manifold with a donut so these would require a little more flexibility downstream in order to stop gasket leaks at the collectors and header to engine bolt up flanges. use a hanger with a longer rubber part if you can because this will allow more flex than some other more rigid rubber mounts. the newer style of rubber ring hangers work pretty good at absorbing vibration and also allowing quite a bit of flex. if using the flexie pipe on headers install where it will be able to deal with the engine movement from torque under load and also deceleration. also make both pipes, on a true dual exhaust, mount roughly in the same area on both sides so the whole exhaust system flexes at the same place and rate. this will give you the least amount of trouble from broken mounts, cracked pipes and leaky flanges. nothing worse than a nice looking truck that sounds like a fish wagon.
personally I like the rubber mounts like these because they are fairly easy to install by yourself and can be taken apart later easily without a worry of a seized u bolt etc. they also allow a bit more system movement than some of the more solid hangers. sometimes you want/need a good stout solid hanger though, so your system doesn't bump other stuff under the vehicle.

https://www.amazon.ca/Dynomax-36317-...56539090&psc=1

https://www.amazon.ca/Walker-Exhaust...92041793&psc=1

https://www.amazon.ca/Pypes-Exhaust-...66408854&psc=1

these styles ensures the pipes or mufflers hang straight and don't want to droop on one side from an offset hanger.

https://www.amazon.ca/Walker-36369-H...91380851&psc=1

https://www.amazon.ca/MBRP-HG6100-Fr...15102846&psc=1

[mr48chev]

I was originally thinking you were asking about something like the piece in this link. https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

[dsraven]

yeah me too. the flexy thing. the stab your fingers with the freaking wire when you take it off for replacement thing, grrrr (been there, like working with winch cable)

[1project2many]

So...

1) Engine flexes, chassis flexes, exhaust must allow for flexing.
2) Steel changes size approximately 0.000016" per degree, up to an inch for a 9' exhaust system with catalytic converters.

You must allow for engine flex and thermal expansion. Stock systems use a "doughnut" or cone and cup type of seal that allows engine rotation. I have found that installing a cup/cone coupling into a vehicle with headers improves header gasket and exhaust system life considerably. When it comes to exhaust pipe hangers they must be installed so that the exhaust can move fore and aft. "Universal" hangers with a single pivot point are not as good a choice imo as the "dual pivot" hangers in the links provided by dsraven. In most cases with RWD vehicles the flexible mesh pipe is not needed. It is used in front drive vehicles to account for high degree of engine rotation which results in both fore and aft and vertical motion at the exhaust coupling.

[MiraclePieCo]

On semi trucks, flex pipe is universally used because the cabs are on airbags, isolated from the frame. I discovered that the mild steel flex pipes quickly break, but the stainless stuff lasts indefinitely.

[b-mac]

I appreciate all the help. And thanks MiraclePie for the kind words.

Manifiolds in pic are what I plan to use, as the fit the cab perfect. They are from the donor '04 Rainer.

The passengers side used the typical donut I'm used to (about 3/4 thick with beveled edged, made out some kind of strange flexible metal).



Drivers side bolts flange to flang with copper o-ring. New to me...hope it's flexible enough.



I used the exact hangers that MiraclePie suggested. Just tacked them on tonight.

[mr48chev]

Our trucks don't normally have the mushy mounted engines like a lot of our dailys have. That 2K DTS I have has soft motor mounts on the engine an then the cradle it sits in has soft mounts besides to dampen any vibration or noise from the body. Plus the engine sits sideways.

[_Ogre]

no flexible pipe or connections needed on our trucks, we don't need them
that started when they put 10 lbs of cr@p in a 5 lb box, we have a 20 lb box

as for broken exhaust manifold studs, you can drill them out and use a mapp gas torch to remove them

[vintovka]

Wonder if temporariy attching flex pipes would allow experimentation to decrease cab drone on downward pointing exhaust pipes.