What exhaust systems are people running?

So the old 5th is a bit too quiet for my tastes, and I know that the factory exhaust is restrictive, especially with the factory cats still on it. I want something with better flow, and something noticeable sound-wise, but not open-headers obnoxious. I don't plan on doing any other performance mods to the engine, and I'm keeping a 2bbl on it, so the engine is bone stock. I figure that keeping a single exhaust, just larger diameter, would be ok for a stock 318. Oh, and I do have to keep at least 1 cat on it.

Anyway, I was just wondering what folks were running for an exhaust system, and what do or don't you like about the system? Any other recommendations are welcomed.

The Ford gets 3" race Bullets after to headers, the Plymouth gets 3.5 race bullets and at least to the axle.

2 1/2 inch duel system, 2 1/4 “H” pipe, dump style behind the rear wheels, Super V Flo-Pro mufflers.

The Dyno-Max Super Turbo sounds pretty good. Nice deep rumble at idle and a nice roar on accel but is not overly loud at cruise. They can sometimes cause an interior drone but depends on the engine, single or dual exhaust, etc.
Can't compare my car to yours (sound wise) but I've got Dyno-Max Ultra Flow welded mufflers and they have a nice deep rumble at idle but bark fairly loud (louder than I'd like but it is what it is) on accel and no interior drone. That's with a 500" BB, headers, dual 2 1/2" pipe and no cats. With a single pipe and a cat, it would be quieter but would think it'd still sound nice.

For what it's worth, Ultra Flow's:

Dynomax Ultra Flow is very hard to beat for sound and performance.

My opinion – which you can toss as far as you can, if wanted.
The Holley 2280/6280 flows about the same CFM as a Carter BBD does – which is about 230 CFM. That is the same CFM an (single) exhaust pipe of 1-3/4” in diameter will flow.

Keep in mind, pretty much all auto manufactures will use smaller pipe diameter the father towards the rear of the car – to help with “drone” noise – which is something to keep in mind.

I will need to do some measuring – but I’m fairly sure (but not 100% sure) your existing exhaust manifold exit holes are 1-3/4” in diameter, already (per side).

Again, in my opinion, your existing 318 exhaust manifolds are not a restriction - when using a 2-bbl. Going bigger exhaust pipe won’t hurt a thing – except for amplifying the annoying “drown”.
In most cases, if you taper pipe size down – and noise might be eliminated.
Also, as the exhaust travels down the pipe, it cools a lot. Cool gases take up less space as hot gases do, so (downsizing) smaller pipe is not as restrictive, as one thinks.

Example A: 2” on each side of Y-pipe – after ditching both pre-cats, 2¼” after both pipes merge. 2¼” pipe through the cat and to the muffler. 2” tailpipe (over axle and to bumper.

Example B: 2” on each side of Y-pipe – after ditching both pre-cats, 2¼” after both pipes merge. 2¼” pipe to the cat. 2” from cat to the muffler. 1-7/8” (or 2”) exit from muffler and tailpipe (over axle and to bumper.

Keep in mind the pipe size reduction is what factory’s used to keep drone noise down. If you never experienced this problem – ask around. I’m sure people who currently has this problem (like me) are more than willing to drive you around for you to experience the not so pleasant noise (which is not necessarily related to what others hear, outside of vehicle).

Even having 1¾” after muffler will not be a restriction – sense the carburetor (and pre-cats) are the “restrictions”.

I don’t see a problem with getting a larger cat (with a neck up/neck down) like from a newer Hemi – only keep in mind it may take a bit more time for it to get to operating temperature of 700 to 1,200’ F.

If you reside in a non-emission state area – great and more power to you on tossing the two pre-cats.

The US EPA does have some laws that muffler shops HAVE to ABIDE by that I want to mention, in regards to Catalytic Converters:
A “Replacement Cat” can only be installed in the following conditions:
. If the Cat Converter is missing
. If a state or local emissions inspection program has determined that the converter needs replacement.
. If the OEM warranty has expired and a legitimate need for replacement has been appropriately documented.
It is against the law to replace an OEM catalytic converter that is properly functioning.
When a replacement catalytic converter is installed, the EPA also specifies that:
. The replacement cat converter must be installed in the same location as the original one.
. The replacement converter must be of the same type as the original (two-way, three-way, etc.).
. The replacement converter must be the proper one for the vehicle as specified by the manufacture.
. If equipped, the converter must be properly connected to the AIR system.
. The replacement converter must be installed with any other required converter for the application.
. The replacement converter must be accompanied by warranty information card, which must be completed by the converter installer.

I do know that any muffler shop (in the USA) cannot/will not remove a cat converter from the car.

My workaround is to get out the sawzall and have ‘em disappear before car arrives at the muffler shop. Just don’t report the “cat theft” – if you did the removing. When you arrive at muffler shop – just have a memory lapse and say you need new exhaust for your ’72 Dart, or something (you are getting this done for your ’72 Dart, are you not – and don’t answer that where someone else can hear you).


I got lucky and found a ’80 Aspen 318 2-bbl with a fairly new exhaust system on it (less the cat, which was cut off), at a pull-a-part by me. The Y-pipe "is like" the newer Canadian Y-pipes are and has no pre-Cats. Note: it looks identical to the Y-pipe on my ’77 Volare.
I’m going to install it myself on one of my cars and the missing cat – might get have to be replaced with pipe – if I can’t find a replacement, first (I'm not going to look very hard).

The plan is to change the exhaust at same time as the 8¼” differential is getting installed.
BudW

An interior drone at cruise will drive you absolutely insane. Makes it so you almost hate to drive the car any distance. Trust me! When you can't hear the radio or even talk to the person in the passenger seat without yelling, it sucks. Should be obvious I had a drone before changing to the Ultra-Flow welded mufflers. Got rid of the drone (well, 90% of it anyway) but not the insanity part

I bought my ’97 ¾ Ton pickup in eBay in New Orleans, one year before (OK, it was 11 months before) Hurricane Katrina hit New Orleans.
The trip to pick up the vehicle is a wild story in of itself (not the truck or anything to do with eBay – but the town and the events on the trip back).

Unknown to me, the previous owner had the 30 gallon drum size muffler removed and had installed 4” exhaust going to rear after the triangle shaped Cat Converter. So, after turbocharge and cat, it is 4” straight pipe (stock is 3½”, after Cat).
From the outside, can’t tell vehicle doesn’t have a muffler on it at idle or at WOT. BUT, between 2,000-2,400 RPM (truck idles at 600 RPM and Redlines at 3,000 RPM) there is a viscous drone noise that comes to play and IT WILL MAKE YOU either speed up or slow down – just to keep out of that range (between 2,000-2,400 RPM).

I’m certain that (finding and) reinstalling the 30 gallon drum shaped muffler will fix that noise concern – but it is just not been a priority.
Come to think about it – I hadn’t been driving that truck as much as I’d like, because of that drone noise.
BudW

dougs headers into 2.5 stainless into 3" y Borla pro xs, Borla resonator, single 3" tailpipe. Sounds great, flows great, no interior drone. Love it.

It gives you something to think about...........

Would have been nice if they had included the decibels

So when they said 'open header' does that mean they had no exhaust system on it?

yep, loud and proud.

I know this is overkill, but I'll tell you anyway.
I have a nice 367 street engine that goes like the dickens. In 1999, I installed TTI headers on it, and dual 3" all-the-way pipes. Under the rear seat are the 3in/3out Dynomax 3pass mufflers. I am very pleased with this system,in every way. Not too loud, and no drone whatsoever, at my cruising rpm of 65=2240
Now I installed that system in 1999. And every winter 5 in a row, I swapped that 367 out for a stock low-compression 1973 318, and ran that for the winter, while I freshened up that bad-boy.
Well not quite stock; I did install a small-port 4bbl intake,an old Thermoquad, and some stiffer valvesprings.
Here's where it gets interesting; That 318 was the most awesome winter engine ever.
I ran it with 3 different transmissions and several different chunks. I think my favorite was the A998 with the wide ratios,and a 2800TC, and 3.55s. That had a starter gear of 2.74x3.55=9.73. Between that,and the 2800TC, that318 still remains one of my favorite all-time combos.
Here's my point.; Everybody ahead of me posted correct information, and I agree with it 100%.....................................but, I can tell you that a 318 running into that freeflowing exhaust went like stink!, with the combo I described above. And with the stiffer springs, she went 5500 easy, still pulling hard in lowgear.And when she hit second she jumped ahead,eager to keep going.
Here's the deal; 5500 is waaay past the power peak for a stock-camed 318. But that a998 has a bit wider ratios. So when I shifted it at say 5200, the Rs dropped to 2920, right about at the torque-peak,and so, that little engine that could, jumped to it.
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I have never had to run cats here in Manitoba, and will never voluntarily do so, And I know nothing about their propensity to drone, But assuming a cat by itself , doesn't drone........... I would run the biggest bad-boy pipes I could find, into the biggest bad-boy cats, mounted where the muffs usually go, and then I would run the second biggest pipes I could find, from there to the back, and then I would turn them down between 30 and 45* .That's what I would do.
And If I thought it was too loud, I would cut some pipe off near the back and swedge the remaining ends down to fit some resonators, and then send the exhaust out thru rectangular ends like the 340 cars had.
But if the cats did drone, I would move them forward and install anyold three-pass muffs in their vacated place.
That's what I would do.
Cuz I know how an old teener runs, when it ain't wheezing thru log manifolds, and into a pipe that is mathematically correct for it.And if you think a 230 rated cfm carb is limited to 230 cfm, well you have probably never installed one on a 340. And if you think a stock318 can only pull the rated cfm of a 230 carb, then ..... well I guess putting an 850rated carb on it was dead-wrong. But I'll tell ya, that stock long-block 1973 low-compression 318really sang.
Your results may vary,cuz I never ran cats,lol.

But if you have one of those 2.20 rears, or a 2.45 rear or even a 2.73 rear, then forgetabout it, it's hopeless. The engine hardly ever gets past 3500, and so basically it could breath thru a straw.At both ends hahaha. Sorry, I couldn't help myself. So for this application I would just put a resonator-tip on the end of the pipe, with a rectangular opening; those kindof burble.

So I am kind of seeing a theme that people like the dynomax mufflers. As far as cats go, I have a buddy of mine that does state inspections, and he told me that all I need is one cat installed. My inspection only is a visual test, so technically I could delete the 2 pre-cats (which I'm doing regardless) and run a gutted cat so it looks like I have one. Since the 318 will more than likely stay stock, What I'm thinking as of now is to run a 2.5 inch system, stock manifolds, one (high flow?) cat, and more than likely some sort of dynomax muffler. I liked the sound of the Ultra flow's in Aspen500's video. I should also mention that I'll just stick with a single exhaust. Thoughts?

That sounds solid
I'm guessing you mean 2.5s from the front merge, and into the cat, out the cat and into the muffler. After the muffler you could go smaller, if it makes it easier to get past the tank.
By the time you get to the bumper you could even put a resonator back there to shape the sound to your liking.
The downpipes from the logs to the merge could be whatever is easiest to snake in there, perhaps down to 1.875.
I saw one fella change the downpipes to what looked like 2.5s as soon as the system got past all the crap. The driver's side crossed over under the bell house, turned South and the two pipes ran side by side half way back, merging just before the single muffler. I can see a cat in each of those front pipes being ok. Especially if they were gutted. But with double the flow, if they're in good shape, you could just leave them be.
I wonder what it would sound like at the bumper with no muffler, just the two cats? or with just one cat..in place of the muffler, and then a resonator at the bumper.Hmmmmmmmmmmmm

Yeah I know, that was helpful as manboobs

I'm running A body headers and the Jegs A body dual exhaust kit. I added an H pipe and cutouts also. All 2 1/2".

Grandmas84 said:

I'm running A body headers and the Jegs A body dual exhaust kit. I added an H pipe and cutouts also. All 2 1/2".

Click to expand...

looks and sounds great!

AJ/FormS said:

I'm guessing you mean 2.5s from the front merge, and into the cat, out the cat and into the muffler. After the muffler you could go smaller, if it makes it easier to get past the tank.

Click to expand...

You got it. I am also planning on sticking with clamps so that if I want to change the system at all, I don't have to cut it.

As always, thanks for the advice guys.

I have Hooker Super Comp 5115s, Dynomax 2 1/2" Super Turbos, and I'm grabbing a 2 1/2" set of mandrel bent B body Flowmaster tailpipes.... A couple weeks and I'll start chopping. If the tailpipes work more or less great, if not mandrel bends and a whole bunch of welding!
Can the gas tank be moved over one rib WITHOUT modifying the fuel filler neck, or should I pick up a spare and extend it??? My first Cordoba was 2 1/2 out the rear, never moved the tank!

I have heard of a few people who were able to move the tank over a rib, without problems it fuel filler neck, but most people – it is just short enough that it will leak. My thought it if something moves (ie: slight rear end accident, rust settling, etc.,) and it allows enough movement to allow pipe to come out of tank and causes a leak – it could make for a bad day.

Think of this, if one was in accident where someone rear ended you, and the pipe did move outwards. You would have fuel leaking onto someone else’s hot engine. I could go on, but I’ll let you do you use your own imagination . . .

Personally, I think it is worth every effort to extend it and not risk anything like you and or your car going up like a roman candle.


Two ways of extending them: One is two get two pipes, cut and weld together (away from any fuel source). The other is to cut original pipe and use rubber hose/hose clamps for extension.

’66-67 B-body used rubber hoses (more like elbows) and most year Dodge pickups also use filler neck hoses – so no worry or risk to do so. The question is finding the correct size.


While there, I also highly recommend replacing the fuel tank grommet while the filler neck is out.
Dodge part number 4002010. MSRP is $17.10 (US) as of today. It might be cheaper via eBay, maybe.
BudW

Edit: added "bold" to a couple of words at beginning of post, only.