Exhaust Suggestions / Assistance

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SouthernDart

SouthernDart

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Need to hear what you think I should do with my '75 Dart Sport Coupe RestoMod. (Daily Driver)

318 Setup:
Comp Cams K20-220-3 Kit (110 Deg Lobe Separation, .432 Intake Lift and .444 Exhaust Lift)
Edelbrock Performer Intake Manifold
Edelbrock 1404 500 CFM Carburetor
Rear End is a Ford Explorer 8.8" Diff (Disc Brakes ;) ) with 4.1 Gears
Headers are Hooker 5901 HKR Full Length 3 Inch.


I need to design the rest of my Exhaust:

1) Maintain 3" all the way back or reduce (at what point) to 2.5" ??
2) H Piece or X Piece or none?
3) Resonators / Mufflers? (I want a low noise ride, that Roars.... discreetly)
4) Straight out the Back Tail Pipes or should I Dump after Mufflers? or Side Pipespast rear Tires?

Many Thanks in advance.
 
I would think 2.5 inch exhaust would be more than adequate for a 318. Tests I have seen show virtually no difference between an x pipe and an h pipe. The h pipe is a lot cheaper to install. Never had resonators, I like exhaust all the way out back, not as loud inside the car. My two cents.
 
I would reduce to 2.5”. The X-pipe is a little more expensive to do but you will get the best exhaust sound over an H-pipe or true dual exhaust (in my opinion) this is exactly what I plan to do on my build!
 
Just some suggestions from experience with almost the exact setup in the past.

For decent power and performance out of that 318 you will need a bigger carb than a 500cfm (up to 750 maybe) and a 2.5 exhaust off the headers can support around 500hp so I think you will be fine with that, plus there is a fair difference between 2.5 and 3 as far as routing room under the car.

On the exits, H or X in the pipe isn't going to matter a lot, so whichever is easiest or whatever will be fine, but for noise sake you probably want one or the other.
As far as mufflers, this may be where to want to drop some cash.
I wanted the old school Flowmaster sound, but you may consider something like Borla that are a little milder tones but still a bit mean sounding.

Turn downs under the car are loud inside the car from resonating off the floor and can produce a lot of dust that others might find sucks, because you will be getting everyone else's cars dirty.:D
Out the sides behind the tires still have to go over the rear end but other than that they are kind of a personal choice over out the back of the car.

I chose something a little different and came out in front of the tires with a slight up angle and cut on the ends to match the body lines. (more resonation at low speeds but fine on the hiway)
 
I wouldnt go with a 3" on a 318. You would likely loose some torque. You didnt mention heads, valve size, etc. I assume its stock?
 
2-1/2 or 3? Hey I’d do a 2-1/2. I used this kit that fit well, required minor trimming, there mufflers should meet your requirements well. This video(s) are interesting (Start at the 4:00 minute mark and go from there.)
 
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And ....

The summit mufflers are pretty good. If you substitute them, Dyno Max Super Turbos are excellent and a little better, or the Hooker Aero Chambers. Both flow enough for your power level and are good with noise control and decent levels of sound. Been there done that with all 3 mufflers in the summit exhaust system.
 
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And finally....

I like the H pipe for the muscle car sound at low rpm and idle. The Individual pulses rock back-and-forth at the rear.
The X pipe sounds awesome at high rpm. At this idle, it has a steep sound. Balanced.
 
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Voice of dissension yet again. I like a 3" exhaust all the way back. Well......let me clarify. I like the exhaust to stay the same diameter as whatever the collector is on the header.

My primary reason is noise. From a 2.5 to 3" system, you get a LOT more rumble. Plus, IF you lose any discernible power, it will only be RIGHT off idle and you will never notice it. Another plus is, if you ever upgrade the engine or swap to a larger one, you have an exhaust system that can handle it.

My 75 F250 for example has a stone stock, (except intake, carb and HEI distributor), and a crappy 2" exhaust off stock manifolds on the 351M engine. When I finally get around to stabbin this 400 in it, I will put a 3" exhaust system under it. I cannot explain what it is......I am not an exhaust or sound expert, but going from 2.5 to 3" does something to the sound I really like.

I had a 71 Camaro years ago when I worked for the local Toyotee place. Small block 400 blueprinted to 72 LT-1 350 specs. 9.2 compression and the solid lifter off road special 2 cam. Headers and 3" exhaust all the way to the rear.

Every morning I pulled in the parking lot and set alarms off all over the lot. Same in the afternoon when I left. You could FEEL the percussion in the ground standin next to it. It really shook the ground. My truck is gonna do the same I kinda like that. LOL
 
A Jegs exhaust at 2 1/2 inches.
From many years back .....
 
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rumblefish360 said:
A summit exhaust at 2 1/2 inches.
From many years back .....
Click to expand...

That sounds great, Rob... I am guessing the Heart Throb 2.5" Jegs -Scumitt exhaust? Did the Mopar offset front spring relocation , no bolt on there.
 
This is my Duster, I run Doug's headers into the Summit 2.5" system with Dynomax UltraFlow mufflers.


Not so sure I'd go 3", especially since you say "low noise" and "discreet". I can tell you there's nothing "low noise" about my car's set up, it flat out roars. Even right around idle it still has the tendency to set of car alarms as I drive through parking lots. And with the windows down on a long trip I wouldn't want it any louder. It's not terrible inside the car with the windows up, but I also installed FatMat insulation on the entire floor of the car. And you'll want tail pipes too, if you dump it under the car it will be much louder inside.

As for power, you won't lose anything you'll notice either way.
 
Abodybomber said:
That sounds great, Rob... I am guessing the Heart Throb 2.5" Jegs -Scumitt exhaust? Did the Mopar offset front spring relocation , no bolt on there.
Click to expand...
You made me realize my mistake. It is an edited post now with “Jegs” as the exhaust kit used . Stock spring location, fit excellent with minor pipe trimming. It otherwise, bolted right in.
 
rumblefish360 said:
You made me realize my mistake. It is an edited post now with “Jegs” as the exhaust kit used . Stock spring location, fit excellent with minor pipe trimming. It otherwise, bolted right in.
Click to expand...
Yes ,the video was quite good , ( not necessarily , yours ... the guy that was accurate at door hinges. W v... what ever..)
 
My 340 with hi po manifolds into accurate 2.25 inch true dual exhaust with gibson performance exhaust mwa mufflers.



I too wouldnt want it any louder, pretty quiet with windows up, like blu said floor sound/heat barrier deff makes a difference
 
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Video unavailable. What is MWA Mufflers
 
I' pretty happy with the dynomax ultra flo mufflers. Straight through design, the 3" flowing 1300 cfm each.

318? I recommend a jegs 2 1/2 mandrel bent kit w/o mufflers and buy a pair of ultra flo mufflers. The sound is great, deep powerful with the right tone amd volume to keep a convo in the car.

I run a 410 sb w/hedman 1 5/8 headers, full 3" jegs pipe kit, ultra flo. While you'd see a drop in rpm of about 400 between the 3" and 2 1/2 due to way less restriction/back pressure...you'd also lose a lil torque under the cam or the first couple thousand rpms leaving the line with that 318. You don't really wanna give any up, I would think with that small a cid.
 
Rumblefish, those are the Gibson straight through, essentially empty "Mufflers With Attitude" they released a couple of years ago. They are pretty unique, advertised to be low drone (I think I recall), and have a distinctive tone. They should flow a lot of air through them!
 
Thanks Tom I looked up mva in the search bar and found them. They kind of look like they would do the job David Vizard was talking about to have a pulse wave ending spot.

Of course that would be at a certain pipe length after the collector.
 
Me, I like 3" H pipe, 3" hooker max flow to 2 1/2 tailpipe for street. Performs and sounds good.
 
Well it's done. 4 GlassPack CherryBombs (2 per side 1 Long and One Custom Built @ the Tail)

(Don't forget it's a Daily Driver RestoMod).

 
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