During my research most sources say to use 1/5/8 headers for a street machine-SLP recommends 1-3/4 which one is the recommended size.

 

If you're not pushing your motor beyond a 300 hp limit, than I would go with the 1 5/8" ones as they will give you more torque in the lower rpm's. With the 1 3/4" your engine will breathe better at higher rpm's. If your motor is pushing over 300hp then definitely go with the 1 3/4" or even if you don't have 300hp yet but are planning to.

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Pat Hirsz
www.iit.edu/~hirspat/MyPage2.htm
88 305TBI
Mods:Hooker Aerochamber 3" exhaust, gutted kitty, March pullies, no smog, 180 thermo,
14x4 K&N, 3.42 gears,
Eibach springs with KYB's all around,
Harwood cowl hood, Z-28 wing, fresh paint(black)
120,000 miles, 5spd, T-tops
Run a best of 16.7 @85mph before gears, slp headers on its way

92 RS, 305TBI, auto, 3.08 gears, 180 thermo, glasspack (no muffler)

 

I agree but i heard the 1 5/8" are totally enough even up to 400hp.

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91'1LE Z28
K&N Filter (just getting started)All show no go.For now.

 

Ive been shopping around too,and every one i talked to says they're easier to instal too.More room.

 

If I could do it again, I would get 1 3/4".

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

SLP 1 3/4.

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Looking For:

87 IROC-Z 350 TPI
84 TRANS AM 305 H.O.

 

SLP 1 3/4

 

hooker LT 1 3/4
if you plan on having a lot of hp

SLP 1 3/4
for medium mods

any 1 5/8
little to no mods

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Rick
90 Camaro RS 305 TBI
400 small block, Hooker 1 3/4 LTs, Random Tech Cat, Hooker aero chamber cat back on the way!!
TH700-R4 with Trans-Go shift kit (corvette servo here...but not installed yet)
MacEwen Motorsports White Gauge Overlays
14" K&N X-Stream Open Element
GTS Headlight and Taillight covers
5% Limo Tint all around
Classic White Chevy Bowtie sticker on rear window
http://www.geocities.com/esvalenz

Man if my camaro were a rice-rocket all those mods would give me what...easily 50-60 hp!!!

"Just because I've done it, doesn't mean I knew what I was doing!" - Me

 

lets say that you've got over 300 horsepower hypothetically speaking...and you've still got the manifolds....would the 1 5/8's be better than the manifolds in high rpms? I know that 1 3/4 would be best but i'm curious since i still have manifolds. Thanks

 

The 1 5/8" would be better than manifolds. I think that if you are talking long tubes, then 1 5/8" is plenty for a typical bolt-on L98, but since we are talking shorties I think there is no other choice besides the SLP 1.75". I just ordered a set as a matter of fact, can't wait to get them on. I will probably never exceed 300 rwhp (unless I decide to spray), but I beleive I made the right choice by following SLP's guidelines.

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87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association