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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » 2.5 or 2.25 pipe for 302??

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    3/01/2014 1:42 AM  #1

    Uwiik
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    From: Jakarta-Indonesia
    Registered: 5/01/2013
    Posts: 92

    2.5 or 2.25 pipe for 302??

    302 with 4100 1.12 carb and ported and polished Edelbrock E street alum head, manual trans.
    Should I use 2.5 or 2.25 pipe? I already have JBA 2.5" full system on hand but my mech here said I should go 2.25"??

    1968 'C' Code Coupe, M Yellow, Parchment Interior, Street Or Track IFS, Randalls R&P, JBA & more later
     

    3/01/2014 4:40 AM  #2

    Rudi
    Senior 24-7 FYI Addict

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    From: Stuck in the 50's Welland Ca
    Registered: 4/01/2013
    Posts: 3,992

    Re: 2.5 or 2.25 pipe for 302??

    Uwiik wrote:

    302 with 4100 1.12 carb and ported and polished Edelbrock E street alum head, manual trans.
    Should I use 2.5 or 2.25 pipe? I already have JBA 2.5" full system on hand but my mech here said I should go 2.25"??

     
    If you have the 2.5 use it. Why put out more $$$. The bigger will sound better anyway.

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

    3/01/2014 7:27 AM  #3

    Uwiik
    FYI FORD Member

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    From: Jakarta-Indonesia
    Registered: 5/01/2013
    Posts: 92

    Re: 2.5 or 2.25 pipe for 302??

    Rudi wrote:

    Uwiik wrote:

    302 with 4100 1.12 carb and ported and polished Edelbrock E street alum head, manual trans.
    Should I use 2.5 or 2.25 pipe? I already have JBA 2.5" full system on hand but my mech here said I should go 2.25"??

     
    If you have the 2.5 use it. Why put out more $$$. The bigger will sound better anyway.

    Somebody said I will lose power by having to big of a pipe....with my little engine every bit of extra hp counts...so it is a truth or BS that 2.5" is too big??
     

    1968 'C' Code Coupe, M Yellow, Parchment Interior, Street Or Track IFS, Randalls R&P, JBA & more later
       •Thread Starter
     

    3/01/2014 8:19 AM  #4

    True74yamaha
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    From: Salt Lake City
    Registered: 5/07/2013
    Posts: 2,537

    Re: 2.5 or 2.25 pipe for 302??

    You won't notice any real loss from that much of a pipe gain. On my truck with a cough 350.. I needed new muffler and tail pipe took it in he suggested this magnaflow muffler which is stainless steel and he said the tail pipe would be to. Come to find out he didn't even tell me they went from a 2.25" stock y to muffler and the cat then where they installed the muffler and tail pipe they went to 3" he told me that after it was done. I said um won't I loose a tone off back pressure cause you do need some. He said if I don't love it bring it back and we will replace it all again for free. Any ways it sounds awesome has great torq improvment And I love not having massive drones while driving. And it's nice it still has a bad a idle to though. So going from where your going that extra 1/4" you won't see a big difference. Although that was a big upgrade people did in the day.

     

    3/01/2014 8:21 AM  #5

    66fastback
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    From: Farmers Branch, TX
    Registered: 4/18/2013
    Posts: 46

    Re: 2.5 or 2.25 pipe for 302??

    I would go with the 2 1/2" system that you already have.  Not only is it a good system, but consider that Ford put a 2 1/2" system on the stock 5.0 Mustangs.  Yes it was a more restrictive system, but the engine in those cars were considerably less capable than what you will have.

     

    3/01/2014 8:55 AM  #6

    Derek
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    From: Eatonton GA
    Registered: 4/01/2013
    Posts: 549

    Re: 2.5 or 2.25 pipe for 302??

    Back pressure is ah myth... Read this articlehttp://www.dsmtuners.com/forums/frequently-answered-dsm-questions/168578-exhaust-straight-scoop-backpressure.html

    Last edited by Derek (3/01/2014 8:56 AM)

    It's hard to type "funny"
     

    3/01/2014 1:26 PM  #7

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 6,899

    Re: 2.5 or 2.25 pipe for 302??

    Derek wrote:

    Back pressure is ah myth... Read this articlehttp://www.dsmtuners.com/forums/frequently-answered-dsm-questions/168578-exhaust-straight-scoop-backpressure.html

    X2
    The whole idea behind racing exhaust is to creat a NEGATIVE PRESSURE in the sys. to "suck out" the spent exhaust!
    6s6
    PS Suck-is-goood!
     

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    3/01/2014 6:58 PM  #8

    John
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    Registered: 4/01/2013
    Posts: 118

    Re: 2.5 or 2.25 pipe for 302??

    Derek wrote:

    Back pressure is ah myth... Read this articlehttp://www.dsmtuners.com/forums/frequently-answered-dsm-questions/168578-exhaust-straight-scoop-backpressure.html

    I admit I read that link quickly, but I think the author is dealing with semantics more than science.  Who cares if the casual reader calls it backpressure or scavenging?  No matter what it's called, too big an exhaust will cost torque.

    John

     

    3/01/2014 9:01 PM  #9

    DC
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    From: Marshall, MI
    Registered: 4/01/2013
    Posts: 1,251

    Re: 2.5 or 2.25 pipe for 302??

    Wow! guys, I just went through this with my race Mustang. 306, 10.3 to 1 compression, 282/284 cam at .500 lift, 1 5/8 primary tube headers, 3 inch collector, no mufflers, 600 cfm double pumper, Performer RPM manifold. I ran both the 2.5 and the 2.25 exhaust on the track and could not tell much difference. Lap times were the same. The 2,25 came off the corners a little bit better, but lost out to the 2.5 at the long end. So my take is if you don't like good sound and high revs, go with the 2.25. If you like good sound and high end power, go 2.5.

     

    3/01/2014 10:18 PM  #10

    lowercasesteve
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    From: Auburn, Ca
    Registered: 4/01/2013
    Posts: 1,261

    Re: 2.5 or 2.25 pipe for 302??

    DC wrote:

    Wow! guys, I just went through this with my race Mustang. 306, 10.3 to 1 compression, 282/284 cam at .500 lift, 1 5/8 primary tube headers, 3 inch collector, no mufflers, 600 cfm double pumper, Performer RPM manifold. I ran both the 2.5 and the 2.25 exhaust on the track and could not tell much difference. Lap times were the same. The 2,25 came off the corners a little bit better, but lost out to the 2.5 at the long end. So my take is if you don't like good sound and high revs, go with the 2.25. If you like good sound and high end power, go 2.5.

    DC, I like the way you think!

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    3/01/2014 10:53 PM  #11

    6sally6
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    From: Surfside Beach,SC
    Registered: 4/02/2013
    Posts: 6,899

    Re: 2.5 or 2.25 pipe for 302??

    lowercasesteve wrote:

    DC wrote:

    Wow! guys, I just went through this with my race Mustang. 306, 10.3 to 1 compression, 282/284 cam at .500 lift, 1 5/8 primary tube headers, 3 inch collector, no mufflers, 600 cfm double pumper, Performer RPM manifold. I ran both the 2.5 and the 2.25 exhaust on the track and could not tell much difference. Lap times were the same. The 2,25 came off the corners a little bit better, but lost out to the 2.5 at the long end. So my take is if you don't like good sound and high revs, go with the 2.25. If you like good sound and high end power, go 2.5.

    DC, I like the way you think!

    OR open headers!! Now THAT'S good sound.
    6s6
     

    Get busy Liv'in or get busy Die'n....Host of the 2020 Bash at the Beach/The only Bash that got cancelled  )8
     

    3/02/2014 8:15 AM  #12

    Uwiik
    FYI FORD Member

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    From: Jakarta-Indonesia
    Registered: 5/01/2013
    Posts: 92

    Re: 2.5 or 2.25 pipe for 302??

    Good to know I don't need to spend more money!! Thanks for the peace of mind guys!!!

    1968 'C' Code Coupe, M Yellow, Parchment Interior, Street Or Track IFS, Randalls R&P, JBA & more later
       •Thread Starter
     

    3/03/2014 7:29 AM  #13

    Rudi
    Senior 24-7 FYI Addict

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    From: Stuck in the 50's Welland Ca
    Registered: 4/01/2013
    Posts: 3,992

    Re: 2.5 or 2.25 pipe for 302??

    6sally6 wrote:

    lowercasesteve wrote:

    DC wrote:

    Wow! guys, I just went through this with my race Mustang. 306, 10.3 to 1 compression, 282/284 cam at .500 lift, 1 5/8 primary tube headers, 3 inch collector, no mufflers, 600 cfm double pumper, Performer RPM manifold. I ran both the 2.5 and the 2.25 exhaust on the track and could not tell much difference. Lap times were the same. The 2,25 came off the corners a little bit better, but lost out to the 2.5 at the long end. So my take is if you don't like good sound and high revs, go with the 2.25. If you like good sound and high end power, go 2.5.

    DC, I like the way you think!

    OR open headers!! Now THAT'S good sound.
    6s6
     

    Hey Sal how is your hearing, SAl, SAL, SAL can you hear me!
     

    Good work ain't cheap, Cheap work ain't good!   Simple Man
     

     

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