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Discussion Starter #1
I’m looking to improve the factory exhaust on my ‘87 SS CCC and have the following comments/questions:

I currently have the stock 2 1/4 manifolds, same diameter exhaust downpipes that Y into single (2 1/4 I think) then universal cat, 2/14 back to single transverse muffler with dual out to pipes side exiting behind the rear tires ( basically factory setup).

I do not want to run true duals just yet for a number of reasons and thought of the following options to maintain a closer to stock configuration, low but not loud tone. While I like Flowmasters, not the sound or tone I’m wanting for this car.

Here is my idea/questions:

What about collecting the two 2 1/4 coming off manifolds into a single 3” pipe, through high flow cat to a better transverse mount turbo muffler ( single 3” in, dual 2 1/2 inch out) with rear side exits? The net effect would be increasing the single pipe collector diameter, a slightly better diameter and flow cat, and better transverse muffler.

Please comment and advise oh wise ones :)
 

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Are you running a stock motor or have you added some extra power? I see you're in TX, so I know the law on this one, the biggest thing you can do to improve flow is throw that cat in the trash and replace it with a straight pipe. Any car older than a 94 no longer has to pass emissions and get safety only inspection. If you have the need for more flow, your idea of a larger collector-back pipe and muffler is good, just forget the cat.

Joe
 

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Discussion Starter #3
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Joe

The motor is stock but I’m planning swapping a few Monte Carlo SS bits to her ( heads, cam and intake upgrades) so maybe 20-30 HP at most
 

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Yea, you won't need much more in the exhaust area. Like I said in my first post, just loose the converter and put in a muffler that will give you good flow and sound the way you want it to.

Joe
 

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I did a search a few years back for a set of the old edelbrock tes headers
For them without much issue.

Sent them my local coater and they look like new now

So that is one option too
 

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Keep the stock diameter tubes from front to back, 20-30hp increase in the future will still not warrant an increase of tube size. When you start going over 450-500hp the exhaust Tube size can matter. Anything below that, stock is anyways the best option period.
 

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I’m looking to improve the factory exhaust on my ‘87 SS CCC and have the following comments/questions:

I currently have the stock 2 1/4 manifolds, same diameter exhaust downpipes that Y into single (2 1/4 I think) then universal cat, 2/14 back to single transverse muffler with dual out to pipes side exiting behind the rear tires ( basically factory setup).

I do not want to run true duals just yet for a number of reasons and thought of the following options to maintain a closer to stock configuration, low but not loud tone. While I like Flowmasters, not the sound or tone I’m wanting for this car.

Here is my idea/questions:

What about collecting the two 2 1/4 coming off manifolds into a single 3” pipe, through high flow cat to a better transverse mount turbo muffler ( single 3” in, dual 2 1/2 inch out) with rear side exits? The net effect would be increasing the single pipe collector diameter, a slightly better diameter and flow cat, and better transverse muffler.

Please comment and advise oh wise ones :)
I recently decided to add a dual exhaust to my 85 CCC SS. Not wanting to mess with the exhaust manifolds or stock set up to the Cat, I decided to run a cat back system from Pypes. The issue I ran into was the stock Cat needed to be changed out to one that fits a Monte Carlo SS. The Pypes system wouldn't fit or bolt up to the stock Cat. The system was on sale, but the cost of the Cat negated any savings.

Although Pypes supplies hangers and such, I still had to fabricate the OEM exhaust pipes back to extend the Cat back so it would bolt up to the Pypes system. So for my Elkie, it wasn't as cut and dried as I expected? But then again, what is?

Pypes has several mufflers available depending on the engine HP and how loud you want the exhaust to be.

Bob
 

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The motor is stock but I’m planning swapping a few Monte Carlo SS bits to her ( heads, cam and intake upgrades) so maybe 20-30 HP at most
Willman, sorry for the late reply to your post, but thought it worth mentioning. Since you have an '87 motor, it should be pre-machined for a roller cam- mine was. You can install an LT1 cam and roller lifters, and really wake up that engine. Only thing I had to do was drill and tap three holes in the lifter valley to accommodate the spider hold down- easy with a drill and hand held tap. You can tell if your's is capable if it has a machined front on the cam hold down area, with a couple of tapped holes there ( for the cam retainer). That cam, along with the MCSS heads, will be a vast improvement.
 

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Are you running a stock motor or have you added some extra power? I see you're in TX, so I know the law on this one, the biggest thing you can do to improve flow is throw that cat in the trash and replace it with a straight pipe. Any car older than a 94 no longer has to pass emissions and get safety only inspection. If you have the need for more flow, your idea of a larger collector-back pipe and muffler is good, just forget the cat.

Joe
Cats really don't rob any power unless they are clogged. Not running them just makes the exhaust smell and the engine to pollute a lot more than necessary. I'm not sure what the big problem people have with running cats. High flow cats lessen emissions, keep the car from smelling like a gas can and don't impact power in appreciable way.
 

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Cats really don't rob any power unless they are clogged. Not running them just makes the exhaust smell and the engine to pollute a lot more than necessary. I'm not sure what the big problem people have with running cats. High flow cats lessen emissions, keep the car from smelling like a gas can and don't impact power in appreciable way.
Not saying you are wrong in regards to cleanliness, but I'd like to see data to back up this statement. I agree that "cat-less" stinks, mine was noticeable when traveling behind the car, so my wife said.
 

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Not saying you are wrong in regards to cleanliness, but I'd like to see data to back up this statement. I agree that "cat-less" stinks, mine was noticeable when traveling behind the car, so my wife said.
Here is a video where high flow cats were added and the car was dynoed before and after. It gained 3 hp and the torque was the same.

Here is a modern muscle car that also had zero change running test pipes in place of the converters.

There are plenty of other examples.

I am sure if you are building a drag racing car with 1000 hp you may not run cats. But a street car making modest power? You would never know the difference AND the car wouldn't stink.
 

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Cats really don't rob any power unless they are clogged. Not running them just makes the exhaust smell and the engine to pollute a lot more than necessary. I'm not sure what the big problem people have with running cats. High flow cats lessen emissions, keep the car from smelling like a gas can and don't impact power in appreciable way.
Wasn't thinking about buying new high-flow cats when I made my post but I was thinking about a $15 dollar piece of pipe, that would be completely legal in Texas. My ElCo didn't stink after I removed the converter until the POJ carb started falling apart. And even then, it wasn't any worse than any of the re-tuned late model Vettes and Camaros that show up at local runs and at work.

Joe
 

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There are plenty of other examples.

I am sure if you are building a drag racing car with 1000 hp you may not run cats. But a street car making modest power? You would never know the difference AND the car wouldn't stink.
Thanks for that, I actually purchased hi-flo cats when I did my original exhaust, but the exhaust shop talked me out of putting them on. Probably because they didn't want to do it. I'll research it some more, I have a different system on it now but its all polished. I may go back and add a couple of cats if there is room for it, shouldn't be too hard to band clamp them and add one to each pipe. We shall see.
 

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Not intending to start any arguments, but regardless of the only 2-3 HP gain, I would never spend the money adding cats if they were not required. If you park indoors, and only drive it a few times per year, do what you want. Mine is a daily driver, parked outside. I have no desire to hop in in the morning, only to find that someone has been underneath and cut it out for the scrap value.
 

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Deleted what I wrote because I didn't read far enough into the thread to see you already made your choice on your exhaust.
 

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Discussion Starter #17
What did you decide, I was search for a similar setup
I went 2 1/2 off the stock manifolds into a single 3" Y, high flow cat, then all the way out to a transverse mount magnaflow (3"in, dual 2 1/2 out). Dyno results were +6HP and +5 ft/lbs torque. A very good start and the tone is low, moderately quiet and gives a nice commanding roar when 4bbl is full on
 
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