1965 GTO Exhaust Options - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 02-18-2014, 02:24 PM Thread Starter
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1965 GTO Exhaust Options

I was wondering what the exhaust recommendations were for a 1965 GTO tripower with a 400cu in motor? It has stock mufflers now and doesn't sound like I'd like. Would like to hear the rumble more and hopefully get some performance bump. What would you experts suggest? It has exhause splitters on each side of the car. Maybe I should just order the new exhaust mufflers and have a muffler shop put them on? Paul.
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post #2 of 4 (permalink) Old 02-20-2014, 10:48 AM
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It all depends on your budget and how particular you are about the sound you are looking for.

For about $100-200 you can get new mufflers welded/clamped in and have a nice rumble. Flowmaster, Magnafow, Dynomax, Pypes are one of many companies out there that design quality mufflers.

Now, if you decide to get longtube headers (replacing your "log style" exhaust manifolds for long piping called headers, usually cost $300-700 depending on brand, quality, material such as stainless steel vs. coated/bare steel) they are usually a pain to get installed, but will give your car a ROAR. Combined with a nice sounding muffler, you will have a great sound.

If you want to go all-out, you could get longtube headers, custom exhaust piping (typically 2.5 inch, unless you're making 500+ horsepower) into an "x-pipe" or "H-pipe" if you desire, which is literally a pipe in an X or H shape, your muffler of choice, then that same 2.5 inch piping out the back with your favorite looking exhaust tips. This route can cost roughly $600-$2000 depending on piping used and labor costs. You will get the exact sound you desire, just the right combination of piping and muffler can give you a mild, deep rumble all the way to obnoxious race-car sounding exhaust and everything in between.

I would consider these the 3 basic levels of exhaust customization. Learn what you can about what brand of mufflers sound like what, you would need to do at least a muffler swap to get a different sound. In general, Flowmaster is loud, old school muscle car sound but doesn't "flow" exhaust gasses as well as other brands, detracting from performance gains.. Magnaflow is very tame, but growls and flows excellently. Generally, most aftermarket mufflers flow better than stock and will provide a mild (1-5 horsepower) bump.

Performance gains:
-Mufflers. Generally a very small gain. Maybe 1-5 horsepower.
-Longtube headers. BEST gains for exhaust. 8-15 horsepower.
-Decent piping. Generally 2.5 inch for most performance cars, expect a few horsepower. This allows exhaust to flow better.
-Tips. As long as you don't get tiny 1 inch Chevy-Bow tie style exhaust tips this shouldn't have any real impact. Almost purely cosmetic. Pick what YOU like best!
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post #3 of 4 (permalink) Old 02-26-2014, 08:57 PM Thread Starter
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GTO Exhaust Options

Thanks so much for your time and knowledge. I feel like I can start thinking about what I want to do now. Before I was just confused! Paul.
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post #4 of 4 (permalink) Old 02-27-2014, 08:34 PM
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Summit makes some reasonably priced 2.5" mandrel bent kits that fit well and are an easy install. They come with a set of turbo mufflers which would be fine for a stock motor, or you can get the performance mufflers to suit your taste. Do a search on youtube and you will find all kinds of video clips of various configurations to see what sound you like. try to find Pontiacs as our motors have a sound unlike others, even the wife can tell a Pontiac from 2 blocks away now . I run the magnaflows because they have a mellow rumble at idle and a nice GRRRRowl when you get into the go pedal. Keep the splitters, they belong on the 65's.

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