Exhaust system for 1975 455 cu.in

[Guest Straight eight]

What would be a good system to replace the original factory exhaust? Replacing with a will fit muffler and resonator produces a nice tone at idle, but acceleration produces a wooshing sound, very unlike Buick. Any clues what might eliminate the whooshing sound short of duals?

[NTX5467]

I would recommend that one place to investigate a factory replacement exhaust system would be someone that has Walker Exhaust products. When the cars were new, they had complete systems available in both single and dual configurations. Being "factory replacement" items, they went on and fit just as the production items from GM did. Walker is still a GM vendor for many exhaust system items.<P>They might not still service the front pipes which attach to the exhaust manifolds, but the rear items (i.e., muffler and tail pipe/resonator) might still be available. NAPA sells these same items under their labeling and the NAPA part numbers match the Walker part numbers, from what I've seen.<P>Maremont is another undercar exhaust vendor that might have the necessary items.<P>In many cases, muffler shop people want to use a generic item and adapt it to most any vehicle. This is also how they typically do dual exhaust conversions too. This is where they get most of their price advantage over using factory-spec items as most people are only interested in money spent instead of authenticity. For many consumers, this works well but the only way to get things "right" in many cases is to use factory-spec replacement items. Items which can go on with clamps instead of being welded together.<P>I let an allegedly knowledgeable muffler shop talk me into an upgrade on one of my cars. They failed to inform me of how it would work and seemed reluctant to fix it when it did not work. If I'd let them weld it like they wanted to I'd have really been screwed. Ended up costing me double to get it returned to stock configuration. <P>One issue will be just how much pipe under there will have to be replaced due to what the muffler shop did previously to use their "in house" muffler. Hopefully they did not change too much that can't be fixed. <P>NTX5467

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GM offered duals in 75?