If I just took the belt off of my smog pump and gutted my cat and put a 3" piece of piping inside would it make a noticeable performance increase?? I am trying to get my car to breathe better with this new cam I installed.

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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!

 

btt

 

I say you'll feel something... The pipe should let you run with little lowend loss (due to the low restriction in exhaust)... I gutted my cat and stuck a pipe in there..haven't removed smog yet...but soon...So ya, i say you'll feel a little something...personally i felt more lowend power but everyone says you lose lowend... heh...i must be an acception...

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89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Problems every other day with the car (probably not a mod, but to me it sure makes a difference)

 

Dan87,

yes you will get a measurable power increase. I would say in the neighborhood of 15hp.

As long as you run through your muffler you will not lose a significant amount of low-end power.

ODB

 

I didn't notice any performance gain by disconnecting the air pump belt. Then again I didn't feel any gain from a new cat back and off road pipe. I'm sure there is some power gained but I couldn't tell.

 

my cat is hollow, and i didn't put a pipe inside it. i have heard that it is bad to just run a hollow cat. is that true?

 

Yes, it is "bad" to have a hollow cat for performance reasons. The gases inside the converter are very hot and thus expand rapidly. When they enter the cat, they are compact, then when they hit the hollow part, they expand, but then they must contract again to exit the cat and flow through the rest of the exhaust system. The problem lies in the fact where the gases have to contract again and that takes energy and time and thus hinders your perfomance.

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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!

 

soo what is the best way to pound a 3" pipe inside of it without ruining it? i would get rid of it but i got pulled over one time, and cause i have a loud exhaust( flowmaster cat-back and edelbrock headers) he looked under my car to see if i had a converter. so obviously i need to keep it, to fool the fuzz. do i just slit each end of the cat(on the side facing the floorpan of the car so you can't see it) open it up and slide a 3" pipe in, and connect my y-pipe and intermediate pipe to the 3" pipe? would that work?

 

Thats pretty much what I plan to do if I decide to gut my cat. I'm thinking about freezeing the pipe before I slide it in so its shrunk down and will slide in easier.

------------------
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!