82 dual exhaust

[cobrajoe74]

RQB3535 needs a new exhaust system. In addition to the hole in one of the downpipes, my mechanic tells me I should get rid of the huge 27 year old catalytic converter as it's probably clogged and robbing the 305 of some HP (as if it can afford to lose any!!)...the beauty of living in SoFla is we have no inspection, emissions or otherwise... I'm thinking of having one of the custom muffler shops in town fabricate the system as the true dual exhaust systems advertised in the AOAI magazine are for earlier years before cats...my questions are: 1) would any of these pre-made dual exhausts fit my 82 (as all the pre-cat cars had bigger motors)? 2) has anybody tried/found a set of "hugger" headers that fit the 305 in the A-II? 3) I'm thinking of Flowmaster 50 series if they fit (I heard a Nissan V8 pickup with these the other day-nice mellow sound that I think I like better than Magnaflows)...the 50's are supposed to be quieter both inside & outside-anybody have these? I'm also thinking of adding a new Edelbrock intake & carb (600 or 650 CFM) and losing the current factory carb with the ancient ECM computer system-any comments/has anyone done this?...Thanks in advance...Joe

[Gunslinger]

Definitely dump the cats! If your car is exempt from emissions inspections go ahead and get rid of them. The dual exhaust systems sold by vendors will fit fine and you can also get a muffler shop fabricate you a set. The dollars involved will tell you which way to go. An advantage to have it fabricated locally is you can specify what diameter pipe to use...2" or 2 1/2". If you stick with the 305 engine, a 2" exhaust may be better and a 2 1/2" may be better for a 350 engine or otherwise higher performance engine. If you want, you can always install a pair of high-flow universal cats...not that expensive anymore and much smaller than the originals.

If you have a local shop fabricate an exhaust system, specify either aluminized steel or stainless steel, not mild steel which will only last a few years. Stainless is more expensive and will last forever. It's also more difficult to work with. Aluminized is easier to work with, less expensive, and will last nearly as long as stainless. Your call on that.

I have Sanderson block hugger headers on my '70 which has a 350 in it. It makes no difference whether a 350 or 305 sits under the hood. The exhaust ports are the same. If you go with headers, no matter what make, get ceramic coated...they'll last longer, look better and control heat better compared to painted steel. I chose Sanderson because of the quality and they have the thickest flanges you'll find...less chance of leaks and bolts that back out.

For mufflers, it depends on what sound you like. I've had both Flowmasters and Magnaflows on different cars. Both are excellent quality. In my experience, Flowmasters have a loud, raspy sound that make you think you'll shatter windows of any neighborhood you drive through. Magnaflows have a deeper, mellower sound that open up at speed. At one time in my life I would pick Flowmasters...now I like Magnaflows better. You can get on their websites and listen to samples of their sounds.

While I think the Rochester Quadrajet is an excellent carburetor, it's electronic computer controlled version can be a nightmare. It's also hard to calibrate after all these years and probably not too many techs out there are experienced enough to do much with it anymore. It also could probably stand being rebuilt, which isn't cheap and few techs really understand a Quadrajet and how to set them up properly. Going to an Edelbrock intake and carburetor is a sound idea. My own recommendation would be to get the Edelbrock Performer EPS intake as it's designed specifically and is optimized for their square bore Performer carbs. The standard Performer intake in designed both for square bore and spread-bore carbs and while good, is not optimized for either. The EPS has better horsepower and torque numbers than the standard Performer. Not a huge amount better, but still an improvement.

Whichever intake you decide, get it without EGR...your current EGR likely doesn't operate properly anymore anyway, losing it and its associated plumbing will do a lot for cleaning up the underhood appearance and will probably run better.

The Performer 600 or 650 carbs would both work fine, though the 600 would likely be a bit better than the 650 for a 305 engine, especially at lower rpm's, plus it's about $100 less expensive. If you have a/c in your car, you'll need the a/c kick-up solenoid. It will be necessary and proprietary to Edelbrock. The Performer 1406 should be just what you need...electric choke and calibrated slightly toward economy, and it will still run better and stronger. Their Performer carbs are easy to adjust and hold their adjustments. If you're looking for pure performance, I think Demon carbs are where it's at, but for a street car Edelbrock is what you want.

The modifications you're considering should really wake that car up.

Edited February 16, 2009 by Gunslinger

[cobrajoe74]

Gunslinger...thanks for the info...I figured you'd be able to tell me what to do!!! I appreciate the info-it really helps! Funny, I thought the Magnaflows were louder-I went on Youtube & listened to some 305's with Flowmaters-the 50's are supposed to be for us older guys.-not as loud outside & with less interior resonance...I've heard some aftermarket exhausts on Mustangs like my 03 Cobra vert & they were obnoxiously (and I suspect illegally) loud. Also, I've been reading about adding an H-pipe for better sound...any ideas???....Thanks again!!! Joe

[Gunslinger]

The sound really depends on which series Flowmaster you use. I have a '69 Corvette 427 and when the subject of mufflers comes up on those forums, most tend to share the same opinion as mine to the sounds of Flowmaster vs. Magnaflow. A car I had Flowmasters on was about the same loudness and tone as my old '63 Avanti with glass packs. Everyone in the area knew when I started it. My '02 Avanti has a factory installed Magnaflow car-back system and it has a wonderful low burble that opens up with speed.

I understand your point about our hearing at our age. I have enough hearing loss from gunfire when I was a law enforcement officer and firearms instructor (hearing protection notwithstanding), and many, many rock concerts when I was younger. I'm paying the price now. That...and I have always liked a car that when you start it, the ground shakes under it.

I'm not sure there's an advantage to an H-pipe or X-pipe for an Avanti. There may simply not be clearance underneath to do so. Between the two, an X-pipe has shown better hp and torque gains, but both show gains over a dual system without the crossover. The crossover pipe allows for balancing out of the power impulses the engine creates through the exhaust, but even though it's measurable, it may not be enough to notice by the "seat of the pants dyno". That's a tough call...if it's something you want to do, see if there's clearance for it and do so. The non-scientific method to determine where to install the crossover is to use a crayon and run a line from the exhaust pipe flange where it meets the header or exhaust manifold, to the muffler. Run the engine to normal operating temperature. Shut it off and check the crayon line. It will have melted and disappeared...where the line becomes visible again is where you locate the crossover pipe. The scientific reason for that I don't understand, that's simply the easy way to determine it.

Regardless of what exhaust you decide to go with, it surely won't sound like some of these sport compacts, or Ricers as I call them. They put those coffee can shaped mufflers on them that sound like a bunch of angry bees. As I said, I like to feel the ground shake under a real car when you start it.

[cobrajoe74]

Sounds like I don't need to worry about the H or X pipe-I'll let the muffler shop decide if it's feasible. In any event-even with the current cat exhaust the old Avanti sounds better than the beat up Honda Civic with the huge wing on the trunk & that awful 4 cylinder exhaust! And the Avanti has Bruce Springsteen coming out of the original Blaupunkt cassette (I am a Jersey boy originally!) instead of bad rap music. Bruuuuuuce....avaaaaaanti- two of my favorite cheers...Joe

[Gunslinger]

Sounds like I don't need to worry about the H or X pipe-I'll let the muffler shop decide if it's feasible. In any event-even with the current cat exhaust the old Avanti sounds better than the beat up Honda Civic with the huge wing on the trunk & that awful 4 cylinder exhaust! And the Avanti has Bruce Springsteen coming out of the original Blaupunkt cassette (I am a Jersey boy originally!) instead of bad rap music. Bruuuuuuce....avaaaaaanti- two of my favorite cheers...Joe

In my '70 I have an Alpine CD/FM stereo with Boston Acoustics speakers and my '02 Avanti has a Monsoon stereo system...quite often ZZ Top and Mountain are blasting out of them (and I complain about hearing loss!).