Need advice on basic exhaust system

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unclepunchy

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Hi Folks,

73 Duster 4spd, with a 383, 516 heads, 9.5:1 comp, stockish cam and HP manifolds.

4CB962AC-863C-4350-AFB4-040E99D551FA.jpeg


Looking for advice on a street/daily driver dual exhaust setup. Nothing crazy and I am hoping to buy a full kit like Summit sells, etc so I could install it myself. Using the HP big block manifolds, no headers. Appreciate the help on this one, no experience with exhaust yet.

Cheers!
 
2 1/2 is fine for your combo.
Flowmaster cheap knockoff are what
I run in my 10 second Street legal mild
Big Block.
 
IF you have a competent exhaust shop near you.....
I would get the summit header back 2 1/2 system for your body, and get a local muffler shop to bend up some headpipes to mate with the summit pipes.
High dollar solution: accurate exhaust or TTI.
Edit: tho I like the Flowmaster sound (some don't, and they do tend to drone) if I were you, I'd use the summit turbo knockoffs that come with the summit kit.
 
Header back kit, it won't matter, get it for your Duster. The engine swap means to me that the manifold back kits might not work. That why I suggested a muffler shop to make headpipes, on your car.
 
I gave Accurate the numbers off my 318 manifolds and had them make me headpipes from manifolds to the crossmember. I then hooked those to the cheap Summit or Jegs header-back system. I think the headpipes were $150 including shipping although it was probably at least 10 years ago.
 
Thanks for the info guys. Would I still get the A body kit even though I am running a 383 or does it matter?
Since the manifolds you're using weren't used on A-Bodies it's likely you'll need some custom work done. Have a shop bend you custom headpipes like 33IMP says, or maybe modify B-Body pipes which should at least have the right manifold outlet angle. Torsion bar and steering clearance is another matter.
 
You're not going to find a totally bolt on kit for a 383 in a 73 A body with I assume B body HP manifolds. You're going to have to get the header back kit and take it to a local exhaust shop, or let the local shop do the whole thing.
 
Okay, some custom work for the manifold end. That’s not a problem. I might call Accurate and see what they can do. I am just waiting on the manifolds, should have them within a week or so.
 
The complete TTI kit is easiest to install yourself and it’s all in one box. X or H pipe. The system can be bought with or without mufflers. They can include them and they will be Dynomax turbos.

TTI also head pipes only if you want. Also tail pipes by themselves. From there you can construct your own exhaust.
 
The shape

X pipe the two parts of the system merge into each other and then away at a point that makes a junction, and that is about the same bore as 1 pipe. the pipes in this area are cut and welded to allow both pipes to communicate with each other. the arangement looks like a cursive writing or Algebra x
to remove the trans you will have in most cases to remove the X section

H pipe the 2 sides of the exhaust follow their own route and are joined by a link between the 2, looks like an H. if you get the link made with slip fit connectors or flanges so you can unbolt it there is a chance that the trans can come out without the exhuast system being completely removed.

the aim here allows pulses from 1 bank of cylniders to influence those on the other bank

the X or H is put at a sweet spot far enough back to allow good extraction of exhaust gas from each cylinder (decent length of none varying bore pipe from port to the X or H but not so close as to disrupt pulses and casue a reversion of exhaust gas back into an apposing cylinder.


on the whole if done right you usually find an increase in torque mid range, which makes the car feel a bit more peppy on the street

and the exhausut note, can make it have less crack to it...

too close to the heads and it wil help with all out power but you will loose some of that mid range torque that you use when street driving

in general the further back you merge the more the torque cuve is biased towards lower RPMs but this only works if the pipe bore is correct

too fat a pipe and the effect is negated

you will gain by the fact that you intend to use cast iron manifolds they hold heat longer and can promote fast gas flow the key here is making sure the pipes from the manifolds to the main system are of appropriate bore to take advantage

for a street car a system too big is worse than one a little too small

drag race and it a whole different kettle of fish

Dave
 
Thanks Dave! Good explanation. I’ll add two duckets….

The X & H pipe also offer a slight change in sound. Very minor.
Being that the exhaust pulses are shared.
The following descriptions apply with with a upgraded and a bit warmed up engine in the power department.

Do note this. Sound through mufflers changes with every muffler and every diameter change when it exits the tail pipe. If you’re unsure of what muffler to run, the best advice I can give is visit various car meets and race tracks for a listen. Ask the cars driver what exhaust they’re running and at what size. Also ask a little about the engine.

The H pipe offers a slightly softer note that comes out the tail pipes equally. The sound becomes fuller, in stereo so to speak. As opposed to the pulses changing from left to right following the firing order.

The H pipe is the true classic muscle car sound. 100%!

The X pipe is also like this but bit quieter at idle and cruise.
But! When you’re at wide open throttle and getting to the higher rpm range of the engine, the exhaust note changes to a shrieking banshee sounding as if the engine is spinning another thousand or so rpm higher.

(Quick story)
I found this out of the wife’s car and it has been advantageous in creating some fear in the next lane to unknowing street challenges brewing. Normally it’s a new fella and/or a young person sending out signals they wanna challenge the ‘67 Cúda to a run. While at advantageous speed, I will drop the trans down a gear, mash the GO pedal and let’er rip forward sending that wonderful sounding shrieking banshee exhaust note into their poor unsuspecting ear freaking them out. That and some rubber smells and smoke.

At one point or another the cars come to a light or slow down enough where I lie a little and tell them, “I got another easy 1500+ rpm of power to unleash on your ***, where can we go?” They’re like “WAAAAAAAATTT????”
I lie a little again and tell them “I only got to 6K on the tach, I need room to really open it up so it can rip!” Truth was I only got to about 5K.
Everyone has declined so far.

Just remember that the X pipe description is on a fairly hot street set up.
The exhaust is TTI headers and exhaust system stem to stern and uses Dynomax turbo mufflers. The system is 2-1/2. Its sound level is pretty good in the car and roars nicely when you’re at WOT.
(Wide Open Throttle)
You can have a conversation in the car with little effort to speak above the interior sound level. Listen to the stereo without wearing out your ears.
 
OH! If you’re looking for a dead stock sound or one with just a minor rumble, your muffler choice is the real dictator of sound.
A longer muffler will be quieter. Dynomax offers a line they call Sound FX. These could probably pass as stock HP mufflers. Under a low compression engine, they’ll probably pass as stock mufflers.

If you can’t get a long enough muffler body case under the car, use a glass pack before the muffler if you can OR at the straight length of tail pipe just before the exhaust tip. Again, the longer the glass pack, the more quite it will be.
 
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