Just because I'm bored in my hotel room on a business trip. I replaced the exhaust on my 1986 Camaro IROC Z with a full Hooker set up a few years ago. The system is made up of Hooker shorty headers, Hooker Y-Pipe and the Hooker Aero Chamber muffler/cat back system. How much horsepower did all of these add? It felt like a night a day difference. I had already did the ram air mods for the TPI prior.

 

Exhaust systems don't "add" horsepower. A free-flowing exhaust system reduces the loss of power compared to a restrictive exhaust system. The amount of power that is freed up depends on the engine itself, and the conditions in which it is operated. Your system may have freed up 15 to 20 horsepower, but without actual dyno testing, it's only a guess...

 

I can tell you this. On a previous Thirdgen I had with a Vortec 350 I ran 14.5s...Later by changing nothing but headers and full 3 in exhaust put me at 13.7s so I would say a lot. 40+ hp would be my guess. But then again as your engine makes more power the exhaust is probably more of an issue.May not be as big a difference on a "stockish" engine.

 

14.8@94mph bone stock L98. 14.4 with a catback. Don't remember the MPH. 14.0@98mph after adding Hooker 2055 headers/y pipe. Car had a 13.9 in it that day though. That was with the wonderful stock 2.77 gears also.

 

Depends on the exhaust you're taking off, and on the motor.

If the exhaust isn't The Bottleneck, then it won't do much. If it is then the effect could be massive. On a motor with good breathing heads & intake and a good cam, the difference would likely be YYYYUUUUUUUUUUUUJJJJJJJJE. Most stock exhausts are pretty pitiful; some are MUCH worse than others. Lots of variables.

 

I agree on a 305 assuming that’s what you had in your 86 tpi car, id say 10-15 whp. Doesnt seem like much but in a car that may only make 180-190 whp, 10-15 or even 20 is noticeable imo

 

There are many Variables that will contribute to the answer...
So there is no simple answer.

Specs, specs, specs!
We need Data, lots of Data.

Once we have information on the Engine...
The current Exhaust System can be analyzed; how much of a restriction is there?
What arrangement are the Primary Tubes in, and what Order are they in?
Exhaust Systems can be very basic, but they can also be VERY COMPLICATED.
There is actually a lot going on with an optimized Exhaust System.

Many people think that running just a simple Set of Tubular-Headers (or Zoomies) and nothing else...
Makes the most Power.
Most of the time that actually not the case.

Simple Collector extensions often are a benefit, longer primaries are often a benefit...
Tri-Y Primary arrangements are, and then altering the order/ arrangement and length of the Primaries are often a significant benefit.

Some Drag Racing Classes require Open-Headers/ Zoomies as a way to limit power, and keep the Cars on a more even field...
Not to help make Power.
A high tech Exhaust System could definitely give an un-fair advantage to some Cars.

We could actually get into a very complicated, many Hours long Discussion about this.

 

Yall are over complicating this lol

 

I've always found exhaust dynamics super interesting, even if it's often dominated by packaging requirements.

I'd wager a free flowing setup with shorty headers might show 10% gains over stock. Long tubes might pick up a little more at the top, but should make noticeably more torque down low from scavenging. As mentioned earlier, it's more about eliminating restriction and increasing extraction than it is 'adding power'.

 

Thanks to modern Technology and Computers...
There are several great Exhaust System Design Programs!

I had one for a very long time...
I wish I could remember what it was called.

 

All those years of education and research. Old age hits and ...PFFT!!!

 

They say your memory is the second thing you lose as you get older.

Now if I could just remember what the first was supposed to be...

 

I bet your wife knows...

 

Actually, a girl suggested that to me once. I had to remind her that my wife is getting old too.

 

I replaced the entire exhaust on my '92 305 TBI. Short ceramic coated headers into true dual 2.25 exhaust with magna flow FX glass packs (no cats). Only other mods I have are open element air filter, and an all aluminum radiator (don't think that adds any HP). I dyno'd the car and got 160 HP to the wheels. There's a thread here where someone in a '91 305 TBI bone stock dyno'd and had 140 WHP. So, I assume my exhaust is mainly making up that difference.

 

I hit 144 on a DynoJet. So right in the same ball park. 15-20 horse is a nice gain...over 10% with just exhaust bolt-ons.

"170hp rated L03 with automatic, I figured less 20% for driveline losses and all original ignition parts with 59k miles. So my optimistic goal was 140hp. But anything in the 130s would have been fine with me.

She made 144hp, so I was satisfied. Gives me a baseline to compare any future mods against."

https://www.thirdgen.org/forums/memb...ml#post6330490

 

Nice. That was my reason to get dyno'd. Wanted a baseline from here before I decided to swap engines or do anything serious to the 305. Still have a 383 swap on the horizon. Real life crap keeps sidelining the bird.