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Discussion Starter · #1 ·
Hi Folks,

Going to order a factory style dual exhaust for my '66 A code 289. Converting it from the single exhaust configuration. And man, the OD I think on that single system is less than 2"...

I've done all the prep work (floor reinforcement, brake lines) and am looking at the factory style setup with Flowmasters. Vendor I'm looking at offers them with the hangar brackets welded on the muffler already.

Only ? remaining is diameter -- I'm thinking 2" will be adequate with stock manifolds and my 460CFM carb.

I'm really more into cruising this car than anything else. So, seem ok?
 

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1966 Mustang Hardtop 289 4 Speed
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I picked up a complete 2-1/4" kit from Virginia Mustang. I already had stainless Magnaflows but decided to try the Turbo's that came with the kit. A lot of folks complimented me on the sound. I would not hesitate to going with 2" if I did it again though. I installed the kit with my car on stands, it was a breeze. Only thing I'd do different though is to use band style clamps. I recently had to drop my exhaust to swap my clutch. I would have had to cut my pipes to remove the intermediate pipes. Instead I had to drop the whole system on the axle. Just food for thought.
 

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I second 2.5”. Usually its all the same price up to 2.5” with 2.5” being the most common. May as well give yourself some head room. 2.5” is good for around 400hp with true duals. Plenty for that 289 and whatever mods you do in the future.
 

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Discussion Starter · #7 ·
I picked up a complete 2-1/4" kit from Virginia Mustang. I already had stainless Magnaflows but decided to try the Turbo's that came with the kit. A lot of folks complimented me on the sound. I would not hesitate to going with 2" if I did it again though. I installed the kit with my car on stands, it was a breeze. Only thing I'd do different though is to use band style clamps. I recently had to drop my exhaust to swap my clutch. I would have had to cut my pipes to remove the intermediate pipes. Instead I had to drop the whole system on the axle. Just food for thought.
Thanks for the tip on band clamps! I may have to take this apart in the future...
 

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^^^ VM makes a good fitting kit.
You need to make sure that its really Mustang floor pan specific to get a really nice fit. There are several subtle kinks that really make system fit nice and easy where 1/4" can mean a rub and good angles or not.
2" Is perfectly fine, thats already more than doubling what you had before. 2 1/2" is overkill for most every need, even those that have headers.
I got 2 1/4" factory bent stuff spec'd for a '69 from NPD, even turndown tips already on the tail;pipes, all the right kinks in the right places and was actually cheaper buying those pieces a la carte leaving out the hype of a named muffler.
 

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2" will be fine. You'll have reduced pressure drop on the exhaust to 1/4 of the single 2". My car was originally single. I put a take off 2" factory style dual exhaust on (someone was restoring their car to stock and they took the dual exhaust off for a single exhaust!). The mufflers that came with it severely reduced inside to maybe 1.5". I replaced them with Summit Turbo mufflers. When all was said and done, the dual exhaust made a significant difference.
 

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I agree, for a 289 2" will be fine. BTW, the single system was also 2". In fact, this was quite common. With proper mufflers (I wish the Ford part was still available) your performance and sound will be just fine. Even the 428 Cobra Jet, and both the BOSS 302 and 429 had 2.25" exhaust. Surely 2.5" tubing was available. I knew a Ford engineer who was so smart it was scary, and he spent a lot of time on exhaust. If he thought 2" was appropriate, it was.
 

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It's much easier to fit a 2" system than a 2.25" or 2.5" system.

You wouldn't think a 1/4 or 1/2 inch makes a big difference, but it does.
 
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I picked up a complete 2-1/4" kit from Virginia Mustang. I already had stainless Magnaflows but decided to try the Turbo's that came with the kit. A lot of folks complimented me on the sound. I would not hesitate to going with 2" if I did it again though. I installed the kit with my car on stands, it was a breeze. Only thing I'd do different though is to use band style clamps. I recently had to drop my exhaust to swap my clutch. I would have had to cut my pipes to remove the intermediate pipes. Instead I had to drop the whole system on the axle. Just food for thought.
Which dual exhaust kit did you my from Virginia Mustang, and will it fit headers or just manifolds?
 

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Unless your 289 is making big power above 6000, 2 or 2 1/4 will be fine. I wanted some mandrel-bent pipe and the pre-formed Flowmaster tails in 2 1/2 is all I found available for a reasonable price but 2 1/2 is hard to get to fit right on the driver side between the leaf spring and the fuel tank.
 

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I would go with 2.25" duals on a stock or mild motor, but 2" will be fine esp if it is stock. There is no need for 2.5" unless the motor is pretty beefy.
 

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I picked up a complete 2-1/4" kit from Virginia Mustang. I already had stainless Magnaflows but decided to try the Turbo's that came with the kit. A lot of folks complimented me on the sound. I would not hesitate to going with 2" if I did it again though. I installed the kit with my car on stands, it was a breeze. Only thing I'd do different though is to use band style clamps. I recently had to drop my exhaust to swap my clutch. I would have had to cut my pipes to remove the intermediate pipes. Instead I had to drop the whole system on the axle. Just food for thought.
I had a shop make the exhaust for a previous car I had, they did one long pipe from beginning to the end (several pipes welded together) and I had to cut the exhaust to drop the engine a few times.
I also used V band clamps. Love those things

By looking at those charts, I guess it's dual 3" for me...... I always thought that would be too big even for the 408w whatever.
 

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67 Fastback T5 331 TCI Frt End, Canted 4 link rear susp
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2 1/2 can be tight going up and over the rear end and out the back. Also, I just took my 50 Series Delta Flow Flowmasters off the car. Just too much drone, and a little louder and "barky" than I liked. I went with DynoMax Superturbo (1/3 the price) and love them.
 

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I had a shop make the exhaust for a previous car I had, they did one long pipe from beginning to the end (several pipes welded together) and I had to cut the exhaust to drop the engine a few times.
I also used V band clamps. Love those things

By looking at those charts, I guess it's dual 3" for me...... I always thought that would be too big even for the 408w whatever.
I'm not sure if boost changes things or not but I've seen guys making 750-900rwhp go from dual 2.5" to 3" and gain no horsepower.
 

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Ed, if you have to buy something, just get the 2 & 1/2 system. You may want it later, and it would really suck to have a nice 2 inch dual system and then have to toss it and upgrade to a 2 & 1/2 system because you were gifted a nice 347 or something. The small engines don't NEED the 2.5 twin setup, but it DOES NOT hurt you in any way, shape, or form. That and the 2.5s generally sound better because the tone is lower. You'll never be unhappy that you picked the larger secondary pipes. LSG
 
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