Okay, I have all the mods listed in my sig,(nothing except freebies really) and my hooker headers are on the way. What sounds like a good mod after the headers? I was thinking either hooker cat-back or runners by SLP. I cannot afford AS&Ms. My goal is 300hp eventually, and I want to exploit the low and midrange torque on the L98. What should I do next? Thanks!

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'83 Firebird 2.8
'89 Firebird Formula 350
2nd owner, red/grey, t-tops, dual cats, and a 3.27:1 rear
K&N, TB bypass, No MAF screens, CAI

 

See my efi webpage.

Ported plenum, in conjunction with modified SLP runners.
http://www.isthq.com/~dan/efi.html

You might also want to consider a Turbine Technologies 2500 RPM stall converter!

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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Turbine Technologies 2500 stall converter, underdrive pulleys, Crane Hi-6 & more.
1.05g skidpad verified.
New best E/T! 14.039 at 100.82 MPH in 41 degree air at Stanton, Michigan.

 

If you haven't already....port your plenum, built a cold air setup, airfoil.

Don't worry about the runners. You'd feel more of a difference spending money on an aftermarket base.

However, if you have all the above free mods...my next mod would be 1.6 roller rockers.


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91 Formula
305 TPI 5speed
1LE/G92/WS6
Custom cold air intake w/K&N, SLP airfoil, ported & polished plenum, TB coolant bypass,Crane AFPR (47psi),94 octane,Crane Extruded Alum. 1.6 full roller rockers, Timing set from 4*BTDC to 10*BTDC,MSD coil,MSD6AL, Holley 9mm Annihilator Laser shot 50 wires, Ac Delco cap,rotor and plugs, Bosch O2sensor, SLP 1 5/8 headers,SLP catback,3:73s,JET 195* fan switch, Macewen white face gauges, Autometer gauges, Zoom hi-performance clutch.
Street legal with stock throttle body, runners,intake manifold,cam, and heads. Coming next..9# Procharger!

 

Definetly do the cat-back first, you should always start with exhaust mods first. The cat-back will do better for your car at this point than will the runners.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission with 2.77:1 Rear End

Current Mods: Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip with 160* Thermostat, 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 : 14.32 @ 97.7mph
(corrected for elevation)

Next on the list: LT4 HOT Cam

 

Port plenum, catback, headers and a shift kit.

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GTA -89:Free flow muffler,dual 3" HF cats, Edelbrock headers, Vette heads, 1.52 RR 7/16, ZZ-9 cam, Big Mouth, AS&M LTR, !plenum, 52 TB, MSD 6AL, TPIS level V prom, Superior shift-kit and all the minor mods. and more to come!
http://www.itv.se/tacs/members_cars/m279/m279.html (Swedish Trans Am Club)

 

Thanks for all the help guys. So it would it be better to do runners once I've ported the plenum and have an aftermarket base, that way there is no bottleneck, right. How does the Hooker cat-back flow? Is it real loud?

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'83 Firebird 2.8
'89 Firebird Formula 350
2nd owner, red/grey, t-tops, dual cats, and a 3.27:1 rear
K&N, TB bypass, No MAF screens, CAI

 

I've got the Hooker cat-back on my car. Check out my website, as I have .wav sounds available for you. It's pretty aggressive, I must say! I've gone a whole summer in Meridian township without ever having the police look at me twice, so it can't be ThAT loud....



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Daniel Burk
http://www.isthq.com/~dan/fcar.html
'84 Trans Am WS6/L69
KB SFC, Moser axles, Torsen Diff. PST suspension, Braided stainless brake lines, Koni struts, 11-inch rear disks,Spohn Adj. torque arm,
Ported 305 heads w/1.94"intake valves, Comp Cams XE262H, Griffen alum. radiator,
Turbine Technologies 2500 stall converter, underdrive pulleys, Crane Hi-6 & more.
1.05g skidpad verified.
New best E/T! 14.039 at 100.82 MPH in 41 degree air at Stanton, Michigan.

 

As far as intake, the base really is the first place you should start, but you'll see bigger gains if you replace the base and the runners (and port the plenum, though this is the least of all restrictions, but is also the cheapeast mod by far if you do it yourself) The TPI intake is one of those situations where the end result is greater then the sum of all it's parts. Any restriction in the intake will cut down on power. Only after removing all restrictions will you see a big gain in power.

At this point, I'd also say your biggest restriction in the system as a whole is your TPI intake, especially once you put the headers in.

 

Finish the exhaust system. I know it's tempting to do the headers and move on to something else, but you will kick yourself later if you do. Choose whatever cat-back system you want and do it all at once. It will be easier and less frustrating/expensive in the long run. You should also seriously consider replacing the converter if you haven't already (assuming you still run one). Most people don't have the ability to do much exhaust work themselves, and if you're paying for the installation it will make the job a little easier for them and less painful for your wallet. The fewer pieces you have to try and reuse the faster and easier the job will be, no matter who does the job. Later, Rob.

 

So does anyone know what the average muffler shop would charge to install a set of headers and a cat-back?

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'83 Firebird 2.8
'89 Firebird Formula 350
2nd owner, red/grey, t-tops, dual cats, and a 3.27:1 rear
K&N, TB bypass, No MAF screens, CAI

 

Install the headers yourself. That's going to save you several hundred dollars. The remainder of the system will probably cost about $100 to install.

I installed the headers and the Y-pipe, then took the remaining pieces to the muffler shop for installation. They welded it all together before I could ask for clamps, and I was stuck with an intermediate pipe that hit the axle on every bump. I eventually cut the pipes with a sawzall and re-did the job to make it right. So, be careful when you have an outside shop do it, and insist that you inspect the alignment before they weld it together. Consider clamps if you plan on fiddling around with it.