so i put a flowmaster muffler on and some nice exhaust tips, anyway it was not a catback, i just changed the muffler, but like ballpark, how much extra hosepower should the muffler add?

 

Minimal horsepower gains, maybe 1, if you were to redo the exhaust from the heads back, you may notice a little more horsepower, but nothing exceptional

 

just the muffler will give you nothing but sound. Like gozzy said, you would be lucky to get a full horse out of it. if your looking for horsepower, do the full exhaust, depending on what you do, could see a pretty good gain out of it.

 

But it sounds good don't it!

 

So what are some better mufflers that are going to give out more HP or tourque? Dyno max? I'm looking to go true dual and I want more HP sound doesnt matter to me.

 

You need a full cat-back, high flow cat or !cat and headers for max gain...maybe get 10 or so ponies out of that setup...

off topic...Hot-Rodding Magizine put the new Flowmaster American Thunder 2.5" 3.8 Cat-Back on and a before and after dyno showed a 11 rwhp gain...

I don't think those results are typical tho

 

I was going to go from the headers back, true dual. What brand of high flow cats or mufflers would you recommend?

 

true dual from the headers is an impossible task. and after you spends the hundreds trying to figure it out, it will still be crap with no gains. this car was designed to handle a single 3 inch pipe, and thats substantial enough up to 400 hp. the only time you will notice an increase with true duals is in applications with over 500 hp

however, full cat back, you can expect gains of 10-15 hp. the muffler alone would be worth 10 hp, depending on the style. the stock transverse muffler flows as smoothly as a brick. if you have an 84 up, i wouldnt bother with the cat-back system as the car already came with a 3 inch pipe.

shorty headers,y pipe, high flow cat (s), and a muffler, you can look to gain about 30 hp

 

True duals is not an impossible task. It has been done on third gens. In fact there was some one in this forum that has them on thier car and I have seen it done before. You do loose ground clearance though. Must remember to be careful over speed bumps and such.

 

ive seen it done with plenty of clearance, he ran 2 1/4 inch pipes down the driveline tunnel. I cant remember how he had the mufflers ran though, or if he even had them...

i got afull exhaustwith 3 inch exhaust on my 89 ( which came stock with either 2 and a half or 1/4... cant remember, i wanna say 1/4.) By full i mean headers, high flow cat by magnaflow, the pipe, and a 40 series muffler. It sounds sooo nice with my setup. Im runnin mid to upper 300 horse and it sounds like a million bucks, when i get a camera ill record a little revvin action and let yall hear it.