H Pipe Mod
Thread Starter
Racer
Joined: Aug 2004
Posts: 482
Likes: 80
From: Florida, Tampa Bay
H Pipe Mod
I was looking at the stock H pipe while I was lowering the car and bolting up my catback and wondering if anyone has tried enlarging the undersized holes. I was thinking of dropping the H pipe, cutting in the middle and using a sawzall and dremel to open up the 5/8 holes. For bolting back up I could get a short length of pipe to fit inside the h pipe where I cut it and use one of the band clamps to put everything back together. I'm sure it won't flow as well as an x-pipe but out of pocket expense should be less than $30. Main reason i'm interested is reduction of the motorboat sound. Any tips or ideas? 
Last edited by smittydog; Oct 15, 2004 at 10:40 AM.
Le Mans Master
Joined: Mar 2002
Posts: 8,466
Likes: 51
St. Jude Donor '17
do you have an aftermarket exhaust? The only comparison ive heard of a motorboat sound is on the corsa indy at idle which to me sounds just fine.
I would not think that it would change much of a difference to enlarge the dime size holes, as they are there for more of an equalizing effect rather than changing the exhaust flow like an x pipe would.
I would not think that it would change much of a difference to enlarge the dime size holes, as they are there for more of an equalizing effect rather than changing the exhaust flow like an x pipe would.
Thread Starter
Racer
Joined: Aug 2004
Posts: 482
Likes: 80
From: Florida, Tampa Bay
I've got the SLP loudmouth and the sound level is good for me it's just a little boaty at idle. I've heard the x-pipe takes a lot of that away and would like to save the 2 to 300 it would cost to put one on the car.
Le Mans Master
Joined: Jun 2004
Posts: 6,269
Likes: 50
From: Dallas Texas
St. Jude Donor '06-'07-'09-'10
Sounds like it might be an interesting experiment. Why don't you try it and post the results. All the X pipes do is expose a larger open area between the pipes. 
Team Owner
Joined: Mar 2001
Posts: 21,325
Likes: 3,841
From: small town in S.E Pa. PA
St. Jude Donor '03-'04
I did this mod four years ago: the 97 and 98 H pipe had a large hole the 99 went with a hole the size of a dime.. I cut it down the middle, used a plasma cutter and made the H section a 2 1/2 inche opening... it made a world of difference,. I rewelded the the center cut and I ran it for several years.. this mod is about 80 % as good as an Xpipe Mod.. when the flanges broke the second time on my intermediate pipe (with h pipe ).. I bought a Corsa X pipe... the pipe offers better scavenging and smoother exhaust pulses,. and a much better welded flanges and a lifetime guarantee.
Team Owner
Joined: Mar 2004
Posts: 58,501
Likes: 1,828
From: Oklahoma City OK
C6 of Year Finalist (appearance mods) 2019
Originally Posted by sxe60
Sounds like it might be an interesting experiment. Why don't you try it and post the results. All the X pipes do is expose a larger open area between the pipes.
Thread Starter
Racer
Joined: Aug 2004
Posts: 482
Likes: 80
From: Florida, Tampa Bay
I'll be upset if I lose too much volume but the motor boat sound hasn't grown on me and i've had the exhaust on for about 4 monthes. I'll give it a shot in a couple of weeks and post some pics when I get done. I'm unclear on the years that had small holes in the connection across the H pipe. Some places I've read only the early 97's had the large holes and some places say all the 97 and 98 had a correct size opening. I can't imagine my 98 has a full opening because it sounds just like a boat at idle. Not doubting anyones knowledge just looking to verify what i've found online. If anyone knows for sure it would save me a some work.
Last edited by smittydog; Oct 15, 2004 at 03:56 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Team Owner
Joined: Mar 2001
Posts: 21,325
Likes: 3,841
From: small town in S.E Pa. PA
St. Jude Donor '03-'04
Originally Posted by smittydog
I'll be upset if I lose too much volume but the motor boat sound hasn't grown on me and i've had the exhaust on for about 4 monthes. I'll give it a shot in a couple of weeks and post some pics when I get done. I'm unclear on the years that had small holes in the connection across the H pipe. Some places I've read only the early 97's had the large holes and some places say all the 97 and 98 had a correct size opening. I can't imagine my 98 has a full opening because it sounds just like a boat at idle. Not doubting anyones knowledge just looking to verify what i've found online. If anyone knows for sure it would save me a some work.
you could remove the h ipe cut it down the middle and like you said with a carbide cutter or a dremil remove all the metal around the existing hole.. then have it welded up.. 15 minutes work.. maybe 30 dollars tops at a muffler shop.. it is effective.,.. take note to your flanges , they may already be cracked though...
Le Mans Master
Joined: Oct 2001
Posts: 6,710
Likes: 2
From: Southern California
How about a magnaflow x-pipe? You can get them for less than $80 shipped off of eBay. These should be welded, though, so not as easy to piece together at home, unless you're willing to clamp together a slightly leaky setup for experimenting.
I have Loudmouths, too, but with the X-Pipe/Resonator. The X-Pipe/Resonator really does smooth out the noise. Maybe too much. I actually like the sound of my Borla-equipped LT1 Camaro a little more than the banshee wail of my C5.
I have Loudmouths, too, but with the X-Pipe/Resonator. The X-Pipe/Resonator really does smooth out the noise. Maybe too much. I actually like the sound of my Borla-equipped LT1 Camaro a little more than the banshee wail of my C5.
