I have been reading up on exhaust. This can be a bad thing as it has put alot of information on the table. One thing that I have read is about back pressure. What I have been reading indicates that when a car is designed the exhaust is matched to how the engine is tuned.

One of the articles says that if you change the backpressure on a stock exhaust that it will affect the fuel to air ratio because of more free flowing exhaust and you have to adjust the motor for this. In some cases it also indicates that you can make your car slower by freeing up the exhaust and not adjusting the fuel/air ratio.

I just want headers, and dual exhaust. Will I see a performance increase on my stock 75 or will I need to make other changes? :confused:

 

It was the first mod I did to my car and it felt faster. I didn't change any thing else and it seemed to help liven up the engine. The sound difference made it feel like a muscle car.

Let me back up I went with dual exhaust and then put headers on after the engine rebuild.

 

I agree. With my 77 it seems quicker and sure does sound better. I do not have headers and I did not re-tune anything

 

I also agree ... I didn't do any engine or carb changes and the duals definitely added power :D

 

It will DEFINENTLY help your power without a doubt........Next will be new heads, cam , intake, carb and on and on and on :cheers:

 

Yeah, and thats the thing. I dont' want to change out the intake, cam, heads at this time. I want to avoid modding it too much right now because of $$$$$. I would like to do it Piece by piece, I just don't want to slow it down any. Sounds like I will be doing this soon then. Emissions free ! YaY !

I will take off that pesky A.I.R pump and related equipment too.





[Modified by flood, 1:00 PM 11/8/2002]

 

:yesnod: :yesnod: :yesnod: :yesnod:

 

I added dual exhaust to my 77. Because of the low HP and torque of the engine, I went with 2 1/4 pipes rather than 2 1/2. This should handle HP up to the high 300's with no adverse affect.

If you go too big, you will negastively impact the low end torque until you engine mods catch up.

Bob

 

In my experience, I lost a little low end torque which I kinda missed, but gained big time in upper RPM power. I also had my comp cams 268h cam at the time too.
-terry

 

Add me to the also agree(s) ... I didn't do any engine or carb changes and the duals definitely added power and noise along with Flowmaster 40's :D

 

go for it! Along with my duels, no cats, headers I got an Edulbrock Performer intake and I had my Carb re-jetted by(Lars).
I deffinitly feel the diffrence. If I stomp the peddal my tires spin for about ten feet. Thats great for a 75 L48.
:cool:

 

It made a difference on my '77. Removed the Cats, went with true duals, Ravin Mufflers, and Hooker Headers. Just NOT the happy with the Ravins.
I didn't want LOUD, but there just NOT loud enough.

Larry :seeya

 

 

This was a thread posted a little while ago that answeres pretty much any question about exhausts for a C3.
http://forums.corvetteforum.com/zero...358192#4358192

 

It felt and sounded like somebody gave my car an enima when I went from stock set up to true duals on my '76................ :D :D :D

 

As can be seen by the above replys, the IMAGINED performance boost obtained with dual exhaust has a direct relation to the SOUND people hear
out their tailpipes. The louder the sound the better the performance boost. Hehe...if that were only true :rolleyes:

Changing from a split Y pipe catalytic setup to "true duals" MAY give you a
5-7 horsepower increase. Headers MAY give you a 5-10 horsepower increase. Without a decent carb/manifold/cam/head package, it's a lot of money to spend for not a lot of horsepower. Don't expect neck-snapping performance increases with this change. Most of the increase will come at the rpm and speeds that you DON'T normally drive. Unless you keep the pedal to the boards all the time :)

Of course, you can put on one of those K&N air filters and get another "instant horsepower" increase :lol:

Dep

 

I agree wholeheartedly with Dep. The vette did not feel any faster to me after the true dual install, possibly because I drive it every day. It is definitely louder in the mid-rpm range.

My car was roughly a tenth of a second faster to sixty. Was this worth $200? Doubtful. I definitely enjoy the sound more, but I think that the dual exhaust install would have been more satisfying on a motor that had power in the higher RPM range. The L-48 CAM runs out of steam @ 3200 rpm. Power peaks @ 3800-4000. The benefits of the exhaust won't be seen till roughly 2500 rpm, so you really won't find much benefit on a stock basemodel engine. With an L-82, however, I could see a greater (5+ hp) benefit over the stock setup. With headers, a cam, and slightly worked heads, a dual exhaust setup (going from 2.5" single to 2.5" dual), would probably be worth a good 20 hp.

I say if you want your car to be faster, and plan a full setup, you should go for duals. If you plan on going with just "cheap tricks", you won't find more than 200-210 hp out of the L-48. I'd expect 235-250(cats vs no cats on the end of the scale) with headers, dual exhaust, high performance intake and good carb.

Basically. Duals are worth it if your engine can live up to it.

-Steve

 

Not always true Dep. often the factory will tune a motor with better exaust, and then kill some of the power but putting more restrictive exaust on it. this is true with LT1s and LS1s. (Very true with L-88 and ZL-1 but thats a diffrent story...) a common gain with an LT1(EFI) with cat back exaust is 15hp. if you did true dual and long tube headers, 20-30 can be seen. but that all depends on altitude, weather or not you got the slow camaro from the factory, how many miles...etc. add a decent intake, throttle body, MAS (MAF?) and a power chip, and you can get 70 hp. matchport the heads to the intake and do a cam, and it goes way up. i may be a little optimistic because i havent worked with an LT1 in a while, but those are roughly the figgures i remember.

the majority(95%) of the time, Dep is absolutely correct. especially with stock C3s. gutting the cat, or removing it dose very little except pollute more, and headers and HO mufflers wont do much unless you have altered the engine.

my engine is choked. i need long tube headers to get max performance. my comp ratio has been upped, my heads ported, and my cam has been upgraded. i could very possibly see a gain of 50 hp by adding headers. that 50 hp would more than likely be up at 4500-6000rpm too. so i wouldnt get a whole lot out of headers for street driving. i would feel it in the lower rpms, yes, and at $250, its very much worth it, but it wouldnt make my car exceptionally faster. but for the sound, and mild increase i say DO IT! :smash:

[edit to respond to steve]

the setup you described for an L-82 would be worth way more than 20hp. (50ish) i have a pretty mild set up and im at 347 brake horsepower. its basically and LT-1(carbed) cam, shaved/ported heads, stock intake with reworked Q-jet, and 2"true dual. im still running stock exaust manifolds though, and when my engine was built it was dynoed at 347 hp. but its the complete opposite of an L-48 (feeling) and more like a really pissed off L-82.

my engine puts out decent low end numbers, but past 3500rpm is where it really wakes up. it kind of kicks you back twice in 1st because the 4.11s get it going pretty quick, but once it hits that magic 3500 its like someone hit a 50 shot of NOS.( NOT NAWS either :D) :cheers: :cheers: :cheers:


[Modified by '79ProwlerOrange, 4:39 AM 11/9/2002]

 

Replacing your stock 2-1-2 exhaust system with duals will be money well spent.
The next inexpensive upgrade would be to modify your timing advance curve. There is a LOT of information available on how to do this.

The Quadrajet on your stock engine should easily compensate for the exhaust change.

Why Exhaust is Big Problem on 75-81 for HP http://corvettefaq.com/c3/ganeyexhaust.htm

The Goodwrench Quest Part I http://www.corvettefaq.com/c3/goodwr...20part%201.htm

Spend a little time on forum member Terry Rudy's website http://www.corvettefaq.com He has fantastic collection of performance and Corvette specific information on his web page.
If your not yet fully convinced that dual exhaust is a good idea, just continue your research and soon you will be sold.



[Modified by MIKER, 6:02 AM 11/9/2002]

 

I do think I meant to write fifty. Looking at my post, there's no way in hell what I described could only be worth 20. :confused:

Oh well. Chalk it up to senility.

-Steve (whose midlife-crisis started at 16...)