masonc

So i have a '92 with a stock lt1. I had a set of custom 3" true dual exhaust pipes with mufflers at the ends from an 87 project car. So i had them slightly changde where they bolt to manifolds so they would fit and i installed them on my car. Yes they rumble like i wanted but I can tell a huge loss in power!! With no converters, do i not have enough back pressure or what? Do i need to go down to 2 and 1/2 inch pipe? I thought the name of the game was more air flow=more power? something is definately not right. i can't even get it to really kick down into passing gear anymore. What am i missing here?

ride250s

Its not just more air flow, its balanced air flow from what I understand. I have an 87 with 3'' exhaust with 3'' random tech high flow CATS, which is then necked down to 2.5'' Corsa mufflers. I had a huge gain in power.

If I were you, I would first try some high flow bullitt CATS like random technology ones, or magnaflow. In my brother's tuner mag there is a CAT article with comparisons between no CATS, Ceramic CATS, and Metallic CATS. No CATS only gained the car 2HP. In my opinion it isn't worth it. CATS will give you back pressure, and it will still be loud. If you buy the Metallic substrait CATS you will only loose 1HP according to the article.

I dont know if your car has pre CAT O2 sensors and post CAT O2 sensors, but if it does, then the way you have your set up now will be making you engine not run right. CATS should give you back the power you are looking for.

Here is what my car sounds like.

http://www.youtube.com/watch?v=RQ6iHeQn5VY

cv67

You need to get more air through the motor to make use of a larger exhaust system. Cat backs add some to a stock Lt1 but not much. L98 moreso because theur systems were so lousy to begin with.
Start modding the motor now

lushdrunk

A huge loss in power from a free flowing exhaust should not happen. My guess is you got somthing going on with ECM, possibly to much heat on the transmission or the exhaust is messing with the kick down cable. If you somehow got the kick down cable out of adjustment it would feel like it lost a huge amount of power

LD85

If you have two holes in your mufflers on each side,,, stuff some steel wool into one pipe on each muffler and see if that helps to create more back pressure, it might help some

you can get it a Home Depot etc,,, roll it into a tight roll, the pound it into the opening with a wooden dowel, them pull it out with long needle nose pliers if it does not work, total cost would we less than $10 to try

87stocker

Having too large of an exhaust might not loose you power, but it will deffinitly move power arround. You will probably notice that you are making more power into the revs, and a loss of torque down low. 3" exhaust is not worth it. You have to be making big hp before 3" is needed. I have a 2.5" true dual setup on my car and the engine made 408hp and 536ftlbs on the dyno. My car pulls realy hard at the bottom, but Im sure I would loose some of that low end torque if I went to 3".

4 stroke engines are tunable by exhaust. Think Dirt bike: Power can be moved arround by changing header length, diameter, aswell as overall muffler length. Its not nessessarily loosing power, its just being moved arround.

Then again I would consider all other posts from these guys aswell, because you may have other issues.

Cheers