Hi, I recently gutted out my cat and have a couple of little questions. First off I have an Edlebrock TES header and cat back system. I gutted out my cat but was not able to fit a 3" exhaust pipe inside of it, it was just too tight. It was really close but it wouldn't go in. Now I know that some people say this causes a little higher noise, but I have in on the car, and I can deal with it. My question is will it cause some sort of bottleneck in the exhaust by having the exhaust come in to this larger than the pipe area then have to go back down to the 3 inch pipe? One other small question. Where the cat meets the intermediate pipe, is there supposed to be a gasket placed there? I notice there is an exhaust leak there, and would like to fix it. Thanks.

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87 GTA 350 L98
K&N filters, beefed up TH-700r4, Accel Manifold, Ported Plenum and Runners, Fuel Press. Regulator 49.5psi, air foil, modified MAF, SLP cold air box, Hypertech Thermomaster chip w/160 thermostat, MSD 6AL and Blaster 3, B&M shift kit & megashifter, Moser Ford 9in Rear with Richmond 3.50 and locker, Edlebrock TES headers and Cat Back,Hotchkis setup in rear, Poly suspension and Koni in the front, relocated MAT, bypassed TB coolant, 300 lbs lighter

Fastest ET's
Stock-0-60 6.8, 1/4 15.0 @ 94
Best-0-60 4.7, 1/4 12.8 @ 112
Norm-0-60 5.2, 1/4 13.2 @ 108

 

to get a pipe to fit inside the cat, take a cut off wheel or saw or something and cut a slit down the side of the pipe. grind away a little metal so that you can bend the pipe into a smaller diameter. Just keep grinding and bending until u can fit it in the cat. not having the pipe in there will cause a big blockage in your exhaust, but it does make it loud as heck which is cool I love how my car sounds with the gutted cat and 2 chamber flows, but i want it louder still. Make sure u grab a heated O2 sensor if your gona run a gutted cat or else u will have problems getting the O2 to work right. good luck man

 

Flowmasters sound better with a high flow cat rather than a gutted cat or straight pipe. IMO

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'88 IROC TPI 355, '69 truck 4-bolt, fully balanced, 9.75:1 compression, fully ported '70 truck heads(for now), Harland Sharp 1.6 Roller Rockers, Comp Cams CS 252AH-12, ported '86 TPI converted to speed density, Crane AFPR, Flowmaster 3in. exhaust, Edelbrock TES headers, all emissions equipment is still intact, plan on burning my own chips, many more mods and parts on the way as time and money permits =(
Best E.T. with TBI 305: 16.11 @ 82mph
Haven't been to track with new motor
If you have any questions on converting from TBI to TPI email me at jdkchevy70@yahoo.com
In memory of Dale Earnhardt, I'll miss cheering for that black #3 on raceday!!!

 

i wanted to gut out my cat. I have a stock exhaust except a flowmaster muffler. I didn't want to spend any money cuz,i'm dropping an engine and getting a whole new exhaust maybe in a couple of months. Will this work,will the check engine light work. Where do i get a heated o2 sensor?