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Old 08-05-2012, 12:26 AM   #1
shenk10
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2.5" or 3" exhaust?

I'm doing an LS2 swap, and max I could ever see performance wise is up to 500 wrhp, so is it worth it to do a 3" or will I loose low end torque now and even then and should just stick with a dual 2.5"? I also plan on doing an H pipe after the transmission. Any advice or knowledge would be greatly appreciated. Thanks.
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1972 Chevy K5 Blazer, 6" Lift, 35x13.5R15, 6.0/6L80E/NP205

1982 Chevy C10 SWB, 2006 LS2/4l70e
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http://67-72chevytrucks.com/vboard/s...d.php?t=439860
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Old 08-05-2012, 12:51 AM   #2
BR3W CITY
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Re: 2.5" or 3" exhaust?

2.5 is enough but 3" wouldn't hurt at that power level, and should you go much further 3 would probably be needed. Its not much more expensive at the beginning, so go three and don't worry about out-pacing it.
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Old 08-05-2012, 10:45 AM   #3
68GMCCustom
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Re: 2.5" or 3" exhaust?

Mines 3". If you're worried about torque just put an x-pipe in instead of an h-pipe. IMHO an x-pipe is a better choice over an h-pipe as its better at scavenging. Putting one in with a 3" exhaust and keeping it all within the frame rails and not hanging below...now that's a little tougher. : lol:
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'68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy
'72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close
'06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD
'18 Kia Sorento - wife's econo-driver
'95 Chevy S10 - reg cab shortbed, LS, 4.3, auto...

my '68's powertrain and chassis build -links broken
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Old 08-05-2012, 11:10 AM   #4
mooseknuckles
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Re: 2.5" or 3" exhaust?

3" all the way, x-over, lays frame, I could post pics, but I'm lazy...
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Old 08-05-2012, 11:55 AM   #5
shenk10
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Re: 2.5" or 3" exhaust?

I might try to do an x then, I thought everyone said it was hard without going below the frame.

mooseknuckles, do you have pictures in your build? I'll just look there and then you wont have to post up pictures.
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1972 Chevy K5 Blazer, 6" Lift, 35x13.5R15, 6.0/6L80E/NP205

1982 Chevy C10 SWB, 2006 LS2/4l70e
In progress....
http://67-72chevytrucks.com/vboard/s...d.php?t=439860
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Old 08-05-2012, 12:49 PM   #6
68GMCCustom
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Re: 2.5" or 3" exhaust?

Quote:
Originally Posted by mooseknuckles View Post
3" all the way, x-over, lays frame, I could post pics, but I'm lazy...

Sure with a square body....67-72's are a little tougher.
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Kurt -

'68 GMC short step - NIB '09 LY6 6.0L crate motor w/mods, NIB '12 crate 4L85e w/billet 3k stall Circle D, 3.73 posi 12 bolt, DynaTech f-swap headers, 3/4 drop, handling mods, etc. - my toy
'72 Chevy LWB C-10 Highlander - 350/350 ps/pb/tilt/ac - not original but close
'06 Chevy TrailBlazerSS - LS2/4L70e - little black hot rod SUV - my DD
'18 Kia Sorento - wife's econo-driver
'95 Chevy S10 - reg cab shortbed, LS, 4.3, auto...

my '68's powertrain and chassis build -links broken
A surprise phase - carb to efi -links broken
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Old 08-05-2012, 01:18 PM   #7
mooseknuckles
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Re: 2.5" or 3" exhaust?

Quote:
Originally Posted by shenk10 View Post
I might try to do an x then, I thought everyone said it was hard without going below the frame.

mooseknuckles, do you have pictures in your build? I'll just look there and then you wont have to post up pictures.
yep...page 44-45 I think....link below.
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