At what point in modifications should I get the 1 3/4" headers? I'm thinking at this point all I need is 1 5/8".



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Gunmetal 89GTA T-Tops L98
700R4 with 3.27 gears, street tires
Best 60 ft: 1.996
Best 1/8th mile: 9.02 @ 76.5mph with 60' time of 2.14
Mods: air filter, hypertech chip, 3" exhaust
Current Mods: 8.8wires, cap, rotor, +4 plugs, MAF screens
Servo

 

Smith,

What tube length are you planning to run? The entire exhaust system needs to be considered before deciding what tube size to use. If you are planning to increase the cam duration and/or valve sizes in the future, you might as well get the larger tubes now. If the displacement, valves, and heads will remain fairly stock, the smaller tubes can provide higher scavenging force than larger tubes. Much of this will also depend on the balance of the exhaust system. If you are installing a complete free-flowing system, the larger tubes will be O.K. If you are staying with a stock cat converter and single small pipe, the smaller tubes and collectors might actually work better for you.

As the ODB has been preaching, a large oriface isn't always the best thing...

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Later,
Vader
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"No matter how hard you try you can't stop us now..."

 

to be honest it's mostly a judgment call on that question.
My opinion is that you've got about 1 second and 10 more MPH to go.
Other factors that would sway my decision is if you swapped heads & cam, or put in a good torque converter, or increased your cubic inches, or put on a power adder.
IMO

 

"As the ODB has been preaching, a large oriface isn't always the best thing..."


cool I've been quoted by Vader.

yep that's right the large tubes would be mostly wasted unless you have a fairly open exhaust from there back. The smaller tubes are higher velocity and scavenge better given the restrictions downstream.

One thing to note is that SLP 1 3/4" shorties have the same 2.5" collector diameter as other 1 5/8" shorties, so there is little chance you'd actually hurt power to any extent with those.
With an f-body the major scavenging doesn't stop in the collector of the shortie header, but continues far down the Y-pipe. The Y-pipes are basically the same for either so little harm could be done by over-doing the primary size with shorties on an fbody.
Going to 1 3/4" full lengths with 3" collectors is for serious power and could definately soften up the bottom end of a stock engine.
aaah i'm rambling.

 

Smith,

Watch out for the ODB guy - he seems to know his she-ot pretty well. If I get down near the Arch, I'll have to look him up and check out his ride.

In the mean time, whatever you do for your header selection, it's probably worth the extra cash to get them coated (inside and out) if you plan to use the car as a daily driver. The extra heat retention of the coating will help the oxygen sensor read better, help the cat(s) work better, and will stay looking good much longer. You'll also reduce the amount of plastic melt going on under the hood.

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Later,
Vader
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"I'm'a do Things My Way - It's My way or the Highway."

 

When I purchased the car, the exhaust had already been changed. There is no catalytic converter, and there was only one cat. to begin with. It is just a 3 nch pipe to a muffler, where it then has dual outlets...less than 3 inches. Would say 2 or 2 1/2", I am not sure. It still has the stock manifolds. Therefore, I believe the exhaust is open. So 1 3/4" SLPs would work fine then...especially since in the long run I want to have a lot of torque and horsepower. I will definetly get them coated as well. What about shorty vs long runner? I'm not sure what the difference is.
Also, can I make my car a dual exhaust car? or am I stuck with my current set up?

BTW...my current exhaust set up sounds very good. Haven't ever heard anything like it.