Big Power loss Dual Exhaust?

I could use some advice with this. Thanks in advance!

I just finished upgrading from a 2-1-2 to the chambered exhaust from Mid America 2.5" with 1 5/8" hookers. There is no exhaust leak, it's a good installation.

The problem is, the vette used to run perfect and bark strong on the 1-2 shift (th350) but now doesn't come close, and idles rough. I lost a lot of torque with the exhaust change. I've messed with the timing and qjet, no change.

Something strange is up, any ideas?

Sounds like the difference in back pressure has totally changed the tuning requirements for your car. The carb needs adjustment if not re-jetting to match the new performance curve.

It could even be too little back pressure. The engine needs a particular amount of back pressure for proper exhaust scavenging and combustion. There could be a mismatch of mufflers to the state of tune. Your car originally had a catalytic converter and the 2-1-2 exhaust system and was tuned to match.

I would think the carb adjustment is the more likely suspect.

|UPDATED|8/14/2004 6:18:27 PM (AZT)|/UPDATED|

I agree, Gunslinger's hit this one on the head.

Good luck with the tweaking.

Alan

You are dealing with an engine that came with a restricted exaust system and tuned for low emmisions.
Now that you have removed the exhaust restriction,your
engine can move a lot more air through it and needs a
corosponding increase of fuel to optimize your new set-up! You have to run a ritch mixture to make power!
Your car is old,think about upgrading the carb and ignition to wake it up! You can't change one thing without affecting other systems.Your car has potential,
you just need to optimize everything.
Happy motoring!
Steve

Thanks everyone for the info. I have some other carbs and intake I need to try out -maybe that will even out the intake/exhaust flows.

what type of mufflers were you running and how do you like the sound of the chambered exhaust? is it much louder?
Hank

Hey Hank51, I was running the 2-1-2 w/ cat and two old rusted out muffs (not sure what brand). The chambered exhaust sounds good and not loud at idle, it's only loud at WOT but still not "too" loud. The interior is quiet. Many people like flowmaster, I would say these sound better than flowmaster - but different.

However, this kit is not a direct bolt in. I got the one for headers. It needs some custom modification on each section to fit well. The pipes around the tranny needed bent a little more, rear turn downs need shortened etc. If anyone is thinking of this kit, I can send pics of the installation since it comes with no instructions. I paid $80 for the customization, welding of seams and H pipe addition (after frame crossover bar).

76x, thanks. I would like to see your installation. I plan on going with either chambered exaust or true duals.
Hank

Installed chambered on my 75 with Hooker SuperComp headers
about 2 years ago. I was concerned about the noise level and
debated on going through with it for several weeks.
Finally decided to go for chambered and it was an excellent
decision.
Noise level can be high when you are getting on it hard, but
it has a mellow sound when your going easy with it. To turn
up the volume you need only tip your right foot forward.

Gunslinger has it right. You may want to add some exhaust restriction for a short time, until you can adjust the carb and perhaps change the intake. Some tuning is in order.