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Before and after horsepower gains

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Old Aug 26, 2006 | 06:54 PM
  #1  
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Before and after horsepower gains

Was wondering if someone could give me an estimate on horsepower gains on my new exhaust I will be putting in. My car is an all stock L69 with the original L69 exhaust. It dynoed at 187 HP and 220 Lb/Ft Torque. Stock specs were 190 HP and 240 Lb/Ft Torque. Dynoed pretty decent for a 22 year old car.

My new exhaust consists of the Hooker 2055's and y-pipe, Catco High Flow cat 9118, 3 inch dynomax i-pipes and a 3 inch chambered muffler in stock location. Turndown after the muffler. Just curious how much, if any, horsepower gains I would recieve from my setup. I am going to get the car dynoed after I do it, but I just want to see some figures before hand. Thanks a lot!
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Old Aug 26, 2006 | 07:15 PM
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From: MANASSAS PARK
Car: 1992 TRANSAM 1989 FORMULA 350
Engine: L-98 350
Transmission: FIRM SHIFTING 700-R4
Axle/Gears: 3.73
My guess 20 to 25 HP.
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Old Aug 26, 2006 | 07:34 PM
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From: Calgary, AB, Canada
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
wow, you dyno-ed very closed to the stock HP #, would that be RWHP though?

I'm excited to hear a real world dyno result of exhaust work. My guess is also ~25HP.
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Old Aug 27, 2006 | 02:32 AM
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Originally Posted by Sonix
wow, you dyno-ed very closed to the stock HP #, would that be RWHP though?

I'm excited to hear a real world dyno result of exhaust work. My guess is also ~25HP.
What do you mean by that? Is it not RWHP? It was on a Dynojet if that helps at all.
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Old Aug 27, 2006 | 06:06 AM
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From: Oslo, Norway
Engine: '85 Monte SS L69 305
Transmission: TH 200-4R
Axle/Gears: 3.23
All dyno's correct the actual measurement to a standardized one using a factor derived from athmospheric pressure, temperature, and humidity. This is in order to be able to compare readings between different places and conditions. A rear wheel dyno such as the DynoJet also often corrects the actual measured rwhp, using a guesstimate of the drivetrain losses, to present an approximation of the crankshaft horsepower. Any correction factors used I expect should be on the dyno slip I hope you received.
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Old Aug 27, 2006 | 03:18 PM
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From: Buffalo, NY
Car: 1988 IROC-Z
Engine: 427 SBC
Transmission: ProBuilt 700R4
Axle/Gears: Moser 12 Bolt / 3.73 TrueTrac
I put on 2055's and Y pipe. Left on the stock catback pipeing with an 80 series muffler. I gained 2 mph in the 1/4 mile.
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Old Aug 27, 2006 | 03:49 PM
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From: Philly, PA
Car: 91 RS, 95 Z28
Engine: 305 tbi, 350 lt1
Transmission: 4l60, 4l60e
Axle/Gears: monsterous 2.73s in both
Originally Posted by DocHoliday
My car is an all stock L69 with the original L69 exhaust. It dynoed at 187 HP and 220 Lb/Ft Torque.
If that is RWHP, that is very impressive for a stock 22 yr old L69
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Old Aug 27, 2006 | 04:39 PM
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Originally Posted by Fullsizewagon
All dyno's correct the actual measurement to a standardized one using a factor derived from athmospheric pressure, temperature, and humidity. This is in order to be able to compare readings between different places and conditions. A rear wheel dyno such as the DynoJet also often corrects the actual measured rwhp, using a guesstimate of the drivetrain losses, to present an approximation of the crankshaft horsepower. Any correction factors used I expect should be on the dyno slip I hope you received.
I never thought to ask the guy who was running the dyno to print out my sheet. I know, probably a bad idea, but it was my first time ever dynoing a car and it was at a dyno day type event for a car club im in. Those numbers I gave are what he told me my car was making. So, are they right or will I never know without the actual sheet?

I know he has a file on the dyno's computer with my pulls, so I will see if he can email them to me to post here. Thanks for the help guys!
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Old Aug 27, 2006 | 09:50 PM
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From: mid GA
Car: 88 IROC
Engine: 305 TPI w/ l98 cam
Transmission: T5 5-speed
Axle/Gears: 3.45 posi disc 9 bolt
i put eldelbrock TES headers on my 305 tpi and i noticed a difference but i highly doubt it was 20-25 HP. i would guess more around 12..
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Old Oct 5, 2006 | 07:21 PM
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From: Glendale, AZ
Car: 4 Mopars total
Engine: Pentastar power
Transmission: T/F and New Process
Axle/Gears: Three 8 3/4's & one 9 1/4
Originally Posted by DocHoliday
a car club im in

That wouldnt be AZFBA would it??
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Old Oct 6, 2006 | 07:10 AM
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From: Hamilton
Car: 1990 IROCZ Camaro
Engine: 350 4bbl, 200cc Heads, 270hr Cam
Transmission: 700R4 w/ Trans-Go shift kit.
Axle/Gears: GM 10 bolt Posi
Originally Posted by maroon88iroc
i put eldelbrock TES headers on my 305 tpi and i noticed a difference but i highly doubt it was 20-25 HP. i would guess more around 12..
Hes not just doing headers, hes doing an entire header-back.

I say 25 too.
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Old Oct 6, 2006 | 08:28 AM
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From: mid GA
Car: 88 IROC
Engine: 305 TPI w/ l98 cam
Transmission: T5 5-speed
Axle/Gears: 3.45 posi disc 9 bolt
Originally Posted by GuitarJunki17
Hes not just doing headers, hes doing an entire header-back.

I say 25 too.
o ok i thought he said just headers. id say 25 is pretty close then. my 305 tpi ran a 15.3 @88 with just a flowmaster catback and stock manifolds and a hypertech chip.
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Old Oct 7, 2006 | 12:06 AM
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From: Hamilton
Car: 1990 IROCZ Camaro
Engine: 350 4bbl, 200cc Heads, 270hr Cam
Transmission: 700R4 w/ Trans-Go shift kit.
Axle/Gears: GM 10 bolt Posi
Originally Posted by maroon88iroc
o ok i thought he said just headers. id say 25 is pretty close then. my 305 tpi ran a 15.3 @88 with just a flowmaster catback and stock manifolds and a hypertech chip.
Ehc, hypertech. I would think you could tap high 14's though, no?
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Old Oct 7, 2006 | 08:18 AM
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Car: 4 Mopars total
Engine: Pentastar power
Transmission: T/F and New Process
Axle/Gears: Three 8 3/4's & one 9 1/4
He probably would if he took that Hypercrap chip out of there. LOL! (just messin around)
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Old Oct 7, 2006 | 08:53 AM
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From: mid GA
Car: 88 IROC
Engine: 305 TPI w/ l98 cam
Transmission: T5 5-speed
Axle/Gears: 3.45 posi disc 9 bolt
Originally Posted by GuitarJunki17
Ehc, hypertech. I would think you could tap high 14's though, no?

what does ehc mean?

o know though, i have heard people complain about the hypertech chips but i paid like 30 bucks for mine b/c i got it used off this website i think. but people complain b/c it lowers your mpg and doesnt give much performance. i no longer have a computer so it doesnt matter.

btw when i ran that 15.3 i had a cracked distributor and the car had sat for 3 years and i didnt do a tune up on it so it could have probably run a high 14 with little thinks like timing and a tune up.
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Old Oct 8, 2006 | 02:02 AM
  #16  
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From: San Antonio, Texas
Car: Red 1984 Z-28
Engine: 4.8 LS
Transmission: 4L60E
Axle/Gears: 3.73
Originally Posted by 84L69TA
That wouldnt be AZFBA would it??
Yeah I am a member there. Went on the Jerome cruise earlier this year, and will be at the dyno day November 14th to see what shes puttin down now. Whats your name on AZFBA?
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Old Oct 8, 2006 | 10:11 AM
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"84L69TA"
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