Dual exhaust recommendations for modded 306cid? - Page 2 - Vintage Mustang Forums
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post #16 of 24 (permalink) Old 06-28-2019, 09:56 AM Thread Starter
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Originally Posted by LSG View Post
Shinobi, you already have the headers ? get a 2 & 1/2 kit and run it all the way OVER the axle and out the back. Don't fall for the small exhaust myth. LSG
Lol never have. Ran straight pipes many times including my 850 rwhp TT C5 Z.

It's more about finding something that sounds good, doesn't restrict my engine upgrades, and fits good around the C4 tranny, over the axle, and between the tank and rear leaf shackle bolts. I used a 4.5 eye rear leaf spring so the car sits a little lower in the rear.
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post #17 of 24 (permalink) Old 06-28-2019, 11:14 AM
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With the 1-5/8" header it almost doesn't matter. I'd either get the system that is the right combo of price, fit and aesthetic for you OR just go 2.5" because it's common and there are many systems available in that size. I wouldn't put too much thought into the science here because we're splitting hairs on a 306 with that size header- nothing after the collector will make much difference one way or the other.
With a 1 5/8” header it almost doesn’t matter. What does that mean?

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post #18 of 24 (permalink) Old 06-28-2019, 11:52 AM
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Originally Posted by Shinobi68 View Post
Lol never have. Ran straight pipes many times including my 850 rwhp TT C5 Z.

It's more about finding something that sounds good, doesn't restrict my engine upgrades, and fits good around the C4 tranny, over the axle, and between the tank and rear leaf shackle bolts. I used a 4.5 eye rear leaf spring so the car sits a little lower in the rear.
Buy some mandrel bent 2 1/2 tail pipes if your local shop does not do mandrel bends. Decide if you want an H-pipe or X-pipe and have your local exhaust shop fab it up. Muffler choice is very subjective but for me I like the H-pipe with a chambered muffler and the X-pipe with a straight thru Muffler.

Last edited by cmefly; 06-28-2019 at 12:00 PM.
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post #19 of 24 (permalink) Old 06-28-2019, 12:46 PM
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With a 1 5/8” header it almost doesn’t matter. What does that mean?
It means that everything is determined before the collector. Driving yourself crazy trying to get 3-5 horsepower out of the rest of the exhaust is not worth the time and effort.
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post #20 of 24 (permalink) Old 06-28-2019, 01:49 PM
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The magnaflow setup in SS was a great pricepoint but they didn't sell it in 2.25, so 2 1/2 I went
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post #21 of 24 (permalink) Old 06-28-2019, 02:01 PM
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Originally Posted by cmefly View Post
Buy some mandrel bent 2 1/2 tail pipes if your local shop does not do mandrel bends. Decide if you want an H-pipe or X-pipe and have your local exhaust shop fab it up. Muffler choice is very subjective but for me I like the H-pipe with a chambered muffler and the X-pipe with a straight thru Muffler.
Just curious, why the H-pipe/chambered, x-pipe/straight-thru preference? Did you notice any difference with popping on decel or was it simply tone?

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post #22 of 24 (permalink) Old 06-28-2019, 02:05 PM
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Just curious, why the H-pipe/chambered, x-pipe/straight-thru preference? Did you notice any difference with popping on decel or was it simply tone?
Simply tone.
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post #23 of 24 (permalink) Old 06-28-2019, 02:23 PM
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With unequal length manifolds or shorties, it's not like it matters whether he's running 2 1/4" or 5". There's not going to be any scavenging to speak of, and he won't be restricted by the exhaust pipe or mufflers.



However, with a good set of Tri-Y or full length headers, 2 1/4" would make a difference. So would 2", but they'd hurt the top end unless it's basically stock. Tuned exhaust IS a thing. =)

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post #24 of 24 (permalink) Old 06-30-2019, 08:41 AM Thread Starter
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Ended up going with the JBA 40 2650 full length 2.5" exhaust system.
Thanks.

Last edited by Shinobi68; 06-30-2019 at 08:45 AM.
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