C3 Dual Exhaust
Thread Starter
Le Mans Master
Joined: Sep 2000
Posts: 7,353
Likes: 2
From: Katy TX
CI 3-4-8 Veteran
St. Jude Donor '07-'09-'12
C3 Dual Exhaust
Hey yall,
I have true duals on my Vette, but it is getting hard to pass emissions, so I want to go back to the y-pipe set up. I have a dual exhaust crossmemeber, was this an option? Will the y-pipe set up fit? Please advise.
I have true duals on my Vette, but it is getting hard to pass emissions, so I want to go back to the y-pipe set up. I have a dual exhaust crossmemeber, was this an option? Will the y-pipe set up fit? Please advise.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Re: C3 Dual Exhaust (VetteBoy1979)
I believe in 1979, they were still using the same frame from previous years that had legally installed duals. So yes, the stock Y-pipe set up should install without any modifications, as the "dual" crossmember was stock.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Re: C3 Dual Exhaust (79MakoL82)
Cat-butt-trophic converters were installed first in '75 and for a cou;le of years or so, the frames were same...2 holes for exhaust....
in '78 they only had ONE exhaust hole....I worked on a friend's 78....
now that exact year/date of change, I"m not sure....
GENE
in '78 they only had ONE exhaust hole....I worked on a friend's 78....
now that exact year/date of change, I"m not sure....
GENE
Team Owner
Joined: Jul 2001
Posts: 61,415
Likes: 478
From: Here to make friends
St. Jude Donor '11, '16-'17
Re: C3 Dual Exhaust (VetteBoy1979)
Too bad you're not in Oregon. I have the stock exhuast on my '79 and don't need to pass emissions. I would be happy to trade. My crossmember does have two holes as well.
Le Mans Master
Joined: Feb 1999
Posts: 5,877
Likes: 1
From: Park Ridge IL
Re: C3 Dual Exhaust (VetteBoy1979)
Too bad we're not closer either, I have front and rear stainless steel y-pipes that are cluttering my garage. Two Flowmaster Delta 50 series mufflers still clamped on the rear y-pipe. If anyone in the Chciago area needs or want them, let me know. I've got a pair of Dynomax Corvette ceramic coated headers as well
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Re: C3 Dual Exhaust (mrvette)
Cat-butt-trophic converters were installed first in '75 and for a cou;le of years or so, the frames were same...2 holes for exhaust....
in '78 they only had ONE exhaust hole....I worked on a friend's 78....
now that exact year/date of change, I"m not sure....
GENE
in '78 they only had ONE exhaust hole....I worked on a friend's 78....
now that exact year/date of change, I"m not sure....
GENE
[Modified by 79MakoL82, 6:27 PM 1/3/2002]
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
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
Re: C3 Dual Exhaust (VetteBoy1979)
Vetteboy: You only have to worry about emissions 2 more times. You'll be exempt in 2004. I think you should be able to sneak by 2 more times??? Most inspection stations don't have a clue as to what to look for. You can pass the idle sniffer easily without a cat.
Le Mans Master
Joined: Dec 2000
Posts: 9,752
Likes: 0
From: Chattanooga TN
St. Jude Donor '08-'09
Re: C3 Dual Exhaust (zwede)
Perhaps you could add 2 converters. Then have the exhaust shop make two "converter-sized" piece of pipe... for off-road use only, of course. :lol:
Burning Brakes
Joined: Aug 2000
Posts: 852
Likes: 0
From: Katy TX
Re: C3 Dual Exhaust (VetteBoy1979)
I am in Houston as well and have duals on my '79 with no problem on the emissions test. They allow 600 ppm hydrocarbon for our model and I have run 250-300 for the past 4 years. Before going to the test center I always change my oil, plugs and air filter and insure that the car is at operating temperature. Give it a try and see if it helps.
Drifting
Joined: Nov 2001
Posts: 1,804
Likes: 0
From: Gettin crazy with the Cheez Whiz! OK
Re: C3 Dual Exhaust (mrvette)
Nope, my 78 has a 2-hole crossmember. I had duals installed a few months ago. Luckily in Oklahoma there aren't as many restrictions. In fact as of last fall we have no state inspection whatsoever.
Melting Slicks
Joined: Apr 2000
Posts: 3,286
Likes: 8
From: San Jose California
Re: C3 Dual Exhaust (VetteBoy1979)
My 79 had 2 holes too. Two pipes and 2 cats should be "bluffable" especially with 2 factory holes in the frame for the pipes. Are they questioning the duals; or, is the smog out the tail pipes getting close to the maximum limit?
If you have to go back to the Y pipe I would suggest using 3" pipe to help offset the loss. One 3" pipe is almost equal in flow area to two 2.25" pipes. I doubt that they would check for original pipe diameter even if they do demand the original configuration.
Chuck
If you have to go back to the Y pipe I would suggest using 3" pipe to help offset the loss. One 3" pipe is almost equal in flow area to two 2.25" pipes. I doubt that they would check for original pipe diameter even if they do demand the original configuration.
Chuck
Melting Slicks
Joined: Aug 2001
Posts: 2,043
Likes: 1
From: Elkhorn WI
Re: C3 Dual Exhaust (vettes)
my '79 has the two hole crossmember...
no inspection here either....gotta love it....but i bet i would pass...high performance engines are usually burning much more efficiently and pass these tests easily...i have some friends that have to pass them in different county..
we change oil, plugs, wires, and dump 93 octane with a fuel additive in it.
they pass everytime with no cats...
I have dynomax headers to duals, crossover, out twin dual-tip monza mufflers.
no inspection here either....gotta love it....but i bet i would pass...high performance engines are usually burning much more efficiently and pass these tests easily...i have some friends that have to pass them in different county..
we change oil, plugs, wires, and dump 93 octane with a fuel additive in it.
they pass everytime with no cats...
I have dynomax headers to duals, crossover, out twin dual-tip monza mufflers.
