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86-91 exhaust retrofit on my 85 - flowmaster/magnaflow/corsa
I've always wanted to install a corsa cat back system on my 85, and after some 15 years on the back burner, I finally completed this project. corsa does not make a cat back system specific to the 84-85 corvette models, mostly due to a different catalytic converter flange designs. I had two options - one, rework the 85's cat to the corsa flange so the two were compatible, or two, completely retrofit the whole system with the 86-91 design. I wanted everything new from the start, and chose the 86-91 configuration. nothing was a show stopper, but I wanted to use "off the shelf" hardware and this required a little creativity and some minor rework.
my first requirement - a complete stainless system from the exhaust manifolds to the mufflers. a second was, mandrel bends on all the exhaust tubing. the first issue was finding a cat-less, stainless, front y-pipe, 2.5 inch, with mandrel bends. most everything available has conventional bends. these pipe bends, most likely, do not affect performance, and probably have minimal impact on flow, but mandrel bends are a much cleaner and better looking design. the only front y-pipe with mandrel bends I found was a three piece assembly from flowmaster (p/n 2010028). It would have been nice to have a one piece y-pipe, but the three piece assembly did allow for a more adjustment, so in reality, it was better to have the three piece design. the 86-91, flowmaster assembly, worked out perfectly and as a side note, came with quality, stainless, band clamps. there was however, one minor clearance issue. it seems, and i'm not 100% sure of this, but the first bend on a factory system, coming off the exhaust manifold, differs slightly from the 84-85 to the 86-91 design with a tighter bend radius most likely from having something to do with the pre-cats. i'm fairly sure the replacement front y-pipes follows this same factory radius. this caused a minor clearance issue on a diagonal brace going from the engine cradle cross member to the RH frame rail. it was an easy fix by trimming about a quarter inch from one section of the channel. there is no issue with the LH side.
from the 2.5 inch header pipes, it went into a 3 inch collector that connected to the main cat. for the main cat, I went with magnaflow (p/n 93941), and this is where the problems started. even though the application is 86-91, it seems the whole cat design is bass-ackwards. top is bottom, and left is right. seems the only thing they got right was in and out! the smog, air tube is on the LH side of the converter where the tube from the engine comes in on the RH side. you would think it would be an easy fix - just flip the converter over. after all, the exhaust gas doesn't know top from bottom - WRONG! the problem is, the exit ball flange of the magnaflow cat is angled slightly and by flipping it over, caused an alignment issue that rippled through the whole exhaust system. I don't know, either it was a manufacturing F-U, poor QA, a dyslectic design and engineering staff, or I got the rare, bazzaro world, export cat. I'm not even sure the ball flange is supposed to be angled. overall, a nice looking product, and nice finish, but, a problem causing fit. anyway, I installed it upside-down, and got everything factory configured, but spent hours and hours and hours, fiddle-phucking around to get a precise, system alignment, from the exhaust manifolds to the tail pipes. it looks like it will work, but I really won't know until I get the car on the road, and everything settles in a bit. this is my second experience with magnaflow, both having install issues.
I did re-use the 85's factory front hanger/heat shield that bolts the transmission tail shaft housing, but had to rework a 86-91 main cat, secondary heat shield for air tube clearance with the magnaflow cat. not sure how important the secondary heat shield is, but I opted to keep it. to connect the cat's air tubes, I used a piece of .5" high temp silicone tubing. I've used this before connecting cats without any problem. at the exhaust manifold ball flange, i used .125 thick, 3/8", stainless washers (McMaster-Carr p/n 98370A019). yeah, I know, the stud is metric, but I wanted a tighter washer ID to stud fit, and opted for U.S. standard. I secured the exhaust pipes with M10-1.5, copper, flange, lock nuts (BMW p/n 18301737774), and hit everything with high temp anti-seize (permatex 77134).
for the corsa cat-back system (p/n 14115) - what can I say - this is my 5th corsa install, and never a problem - always perfect. the only thing I had to purchase to complete the install was the 86-91 rear exhaust hanger that bolted to the "C" support beam. this was a $15-$20, used, part purchase from fleabay. fortunately for me, the mounting holes are in 84-85 support beam, so it was pretty much plug and play. I bought the corsa system on fleabay, used, from a guy that had a lowered 87 - said he had clearance issues, and sounded pretty much like he put it on and took it off. in fact, I found there was minimal exhaust soot in the pipes - it was perfect. the best part - $500 shipped and that included a new set of muffler hangers.
so, after 15 years, I got my exhaust, with around $900 in the whole system. as for flowmaster, and corsa, two thumbs up. for magnaflow, personally I have to give them just an, "OK with issues."
I've always wanted to install a corsa cat back system on my 85. after some 15 years on the back burner, I finally completed this project. corsa does not make a cat back system specific to the 84-85 corvette models, mostly due to a different catalytic converter flange designs. I had two options - one, rework the 85's cat to the corsa flange so the two were compatible, or two, completely retrofit the whole system with the 86-91 design. I chose the 86-91 design since I wanted everything new from the start anyway. nothing was a show stopper, but I wanted to use "off the shelf" hardware, and this required a little creativity and some very minor rework.
my first requirement - a complete stainless system from the exhaust manifolds to the mufflers. a second was, mandrel bends on all the exhaust tubing. the first issue was finding a cat-less, stainless, front y-pipe, 2.5 inch, with mandrel bends . most everything available has conventional bends. these pipe bends, most likely, do not effect performance, and probably have minimal impact on flow, but mandrel bends are a much cleaner and better looking design. the only front y-pipe with mandrel bends I found was a three piece assembly from flowmaster (p/n 2010028). It would have been nice to have a one piece y-pipe, but the three piece design did allow for a more adjustment, so in reality, it was better. the 86-91, flowmaster assembly, worked out perfectly and as a side note, came with quality, stainless, band clamps. there was however, one minor clearance issue. it seems, and i'm not 100% sure of this, but the first bend on a factory system, coming off the exhaust manifold, differs from the 84-85 to the 86-91 design with a tighter bend radius most likely from having something to do with the pre-cats. i'm fairly sure the replacement front y-pipes follows this same factory radius. this caused a minor clearance issue on a diagonal brace going from the engine cradle cross member to the RH frame rail. it was an easy fix by trimming about a quarter inch from one section of the channel. there is no issue with the LH side.
from the 2.5 inch header pipes, it went into a 3 inch collector that connected to the main cat. for the main cat, I went with magnaflow (p/n 93941), and this is where the problems started. even though the application is 86-91, it seems the whole cat design is bass-ackwards. top is bottom, and left is right. seems the only thing they got right was in and out! the smog, air tube is on the LH side of the converter where the tube from the engine comes in on the RH side. you would think it would be an easy fix - just flip the converter over. after all, the exhaust gas doesn't know top from bottom - WRONG! the problem is, the exit ball flange of the magnaflow cat is angled slightly and by flipping it over, caused an alignment issue that rippled through the whole exhaust system. I don't know, either it was a manufacturing F-U, poor QA, a dyslectic design and engineering staff, or I got the rare, bazzaro world, export cat. I'm not even sure the ball flange is supposed to be angled. overall, a nice looking product, and nice finish, but, a problem causing fit. anyway, I installed it upside-down, and got everything factory configured, but I spent hours and hours and hours, fiddle-phucking around to get a precise, system alignment, from the exhaust manifolds to the tail pipes. it looks like it will work, but I really won't know until I get the car on the road, and everything settles in a bit. this is my second experience with magnaflow, both having install issues.
I did re-use the 85's factory front hanger/heat shield that bolts the transmission tail shaft housing, but had to rework an 86-91 main cat, secondary heat shield for air tube clearance with the magnaflow cat. not sure how important the secondary heat shield is, but I opted to keep it. to connect the cat's air tubes, I used a piece of .5" high temp silicone tubing. I've used this before connecting cats without any problem. at the exhaust manifold ball flange, i used, .125 thick, 3/8", stainless washers (McMaster-Carr p/n 98370A019). yeah, I know, the stud is metric, but I wanted a tighter fit, and opted for U.S. standard. I secured the exhaust pipes with M10-1.5, copper, flange, lock nuts (BMW p/n 18301737774), and hit everything with high temp anti-seize (permatex 77134).
for the corsa cat-back system (p/n 14115) - what can I say - this is my 5th corsa install, and I've never had problems - always perfect. the only thing I had to purchase to complete the install was the 86-91 rear exhaust hanger that bolted to the "C" support beam. this was a $15-$20 fleabay, used part purchase. fortunately, the mounting holes are in 84-85 support beam, so it was pretty much plug and play. I bought the corsa system used, on fleabay, from a guy that had a lowered 87. said he had clearance issues, and sounded like he pretty much put it on and took it off. in fact, I found there was minimal exhaust soot in the pipes - it was perfect. now the best part - $500 shipped and that included a new set of muffler hangers.
so, after 15 years, I got my exhaust, with around $900 in the whole system. as for flowmaster, and corsa, two thumbs up. for magnaflow, personally I have to give them just an, "OK with issues."
Great write up as I have an 85 as well. I run the full TPIS exhaust on mine with the with LT headers. Mine has been on for many years and I would like to go true duals all the way back with a Corsa system, but know I would need to retrofit some things in the process. I actually just bought some new TPIS headers recently for the "what if" scenario....I really like their headers and want a new pair just in case. Anyway, interesting thread. You did good with a full Corsa exhaust for that price!!!!
No kidding ; was just looking at your pics on the bigger screen here at home; VERY NICE job keeping the underside looking like a new car! I have had mine since 2001 and the body is in great shape, but your undercarriage has given me a humbling feeling!!
No kidding ; was just looking at your pics on the bigger screen here at home; VERY NICE job keeping the underside looking like a new car! I have had mine since 2001 and the body is in great shape, but your undercarriage has given me a humbling feeling!!
again- great information here.
- most of my friends think I have a problem. i'd rather spend the day on a creeper, under my car, cleaning and detailing, than playing a round of golf. you try to explain it to them, but they just don't understand. to me, it's mental therapy - I have alone time and i'm in my garage! wrenching on these things is as much fun as driving them. my worst fear is becoming a waxer!
OH NOOOOO! Say it aint so Joe! It does look like you buffed few things underneath tho.
Keep me posted on any gatherings down at the 'Coast, one day I might get a chance to run down. I will try to get my bud with a 77 C3 to run down with me, he has the same affliction you do and his car is sweet!
At a 155k that's amazing! Being in FL by the coast and a lot of mileage, how do you keep the aluminum parts looking so new? Do you drive it in the rain?
At a 155k that's amazing! Being in FL by the coast and a lot of mileage, how do you keep the aluminum parts looking so new? Do you drive it in the rain?
Anymore front end pics? I'm impressed!!!!
well, it was a NE ohio car until 2008 - then my son had the car in Sarasota until I got it back in 2014. when you ask, if I drive it in the rain - ??? - hell yes! I've even driven that car a couple times in the snow and driven in 24 of the lower 48! over the years, whenever I would do any major repair work, I would clean and detail the hell out of things. for cleaning the aluminum suspension components, i pretty much use simple green with a (gray) scotch-brite. i originally cleaned the front/rear suspension in 2006 when i did a major brake overhaul, wheel bearings, and u-joints. i recently went over things to repair a rear end leak, and some work on the rear suspension .
Nice write up. And that sure is a nice clean car you have. I've also had great results on the aluminum suspension with simple green and a scotch brite pad.
Wow that thing is clean. What kind of ramps are those?
dambach ramps. I've had those ramps for about 15 years now - paid $200 for the set. they get the bottom of the car about 17-18 inches off the floor with the ramps on one end, and floor jacks/jack stands on the other. i'm thinking those particular ramps are no longer available.
I've always wanted to install a corsa cat back system on my 85. after some 15 years on the back burner, I finally completed this project. corsa does not make a cat back system specific to the 84-85 corvette models, mostly due to a different catalytic converter flange designs. I had two options - one, rework the 85's cat to the corsa flange so the two were compatible, or two, completely retrofit the whole system with the 86-91 design. I chose the 86-91 design since I wanted everything new from the start anyway. nothing was a show stopper, but I wanted to use "off the shelf" hardware, and this required a little creativity and some very minor rework.
my first requirement - a complete stainless system from the exhaust manifolds to the mufflers. a second was, mandrel bends on all the exhaust tubing. the first issue was finding a cat-less, stainless, front y-pipe, 2.5 inch, with mandrel bends . most everything available has conventional bends. these pipe bends, most likely, do not effect performance, and probably have minimal impact on flow, but mandrel bends are a much cleaner and better looking design. the only front y-pipe with mandrel bends I found was a three piece assembly from flowmaster (p/n 2010028). It would have been nice to have a one piece y-pipe, but the three piece design did allow for a more adjustment, so in reality, it was better. the 86-91, flowmaster assembly, worked out perfectly and as a side note, came with quality, stainless, band clamps. there was however, one minor clearance issue. it seems, and i'm not 100% sure of this, but the first bend on a factory system, coming off the exhaust manifold, differs from the 84-85 to the 86-91 design with a tighter bend radius most likely from having something to do with the pre-cats. i'm fairly sure the replacement front y-pipes follows this same factory radius. this caused a minor clearance issue on a diagonal brace going from the engine cradle cross member to the RH frame rail. it was an easy fix by trimming about a quarter inch from one section of the channel. there is no issue with the LH side.
from the 2.5 inch header pipes, it went into a 3 inch collector that connected to the main cat. for the main cat, I went with magnaflow (p/n 93941), and this is where the problems started. even though the application is 86-91, it seems the whole cat design is bass-ackwards. top is bottom, and left is right. seems the only thing they got right was in and out! the smog, air tube is on the LH side of the converter where the tube from the engine comes in on the RH side. you would think it would be an easy fix - just flip the converter over. after all, the exhaust gas doesn't know top from bottom - WRONG! the problem is, the exit ball flange of the magnaflow cat is angled slightly and by flipping it over, caused an alignment issue that rippled through the whole exhaust system. I don't know, either it was a manufacturing F-U, poor QA, a dyslectic design and engineering staff, or I got the rare, bazzaro world, export cat. I'm not even sure the ball flange is supposed to be angled. overall, a nice looking product, and nice finish, but, a problem causing fit. anyway, I installed it upside-down, and got everything factory configured, but I spent hours and hours and hours, fiddle-phucking around to get a precise, system alignment, from the exhaust manifolds to the tail pipes. it looks like it will work, but I really won't know until I get the car on the road, and everything settles in a bit. this is my second experience with magnaflow, both having install issues.
I did re-use the 85's factory front hanger/heat shield that bolts the transmission tail shaft housing, but had to rework an 86-91 main cat, secondary heat shield for air tube clearance with the magnaflow cat. not sure how important the secondary heat shield is, but I opted to keep it. to connect the cat's air tubes, I used a piece of .5" high temp silicone tubing. I've used this before connecting cats without any problem. at the exhaust manifold ball flange, i used, .125 thick, 3/8", stainless washers (McMaster-Carr p/n 98370A019). yeah, I know, the stud is metric, but I wanted a tighter fit, and opted for U.S. standard. I secured the exhaust pipes with M10-1.5, copper, flange, lock nuts (BMW p/n 18301737774), and hit everything with high temp anti-seize (permatex 77134).
for the corsa cat-back system (p/n 14115) - what can I say - this is my 5th corsa install, and I've never had problems - always perfect. the only thing I had to purchase to complete the install was the 86-91 rear exhaust hanger that bolted to the "C" support beam. this was a $15-$20 fleabay, used part purchase. fortunately, the mounting holes are in 84-85 support beam, so it was pretty much plug and play. I bought the corsa system used, on fleabay, from a guy that had a lowered 87. said he had clearance issues, and sounded like he pretty much put it on and took it off. in fact, I found there was minimal exhaust soot in the pipes - it was perfect. now the best part - $500 shipped and that included a new set of muffler hangers.
so, after 15 years, I got my exhaust, with around $900 in the whole system. as for flowmaster, and corsa, two thumbs up. for magnaflow, personally I have to give them just an, "OK with issues."
I have a 95 coupe with the axle back Magnaflows which sound awesome coming into a cruise but the drone on acceleration is killing my ears. The drone is never ending and I wanted to change to corsa or borlas. Let me know how loud the new installs are.
I have a 95 coupe with the axle back Magnaflows which sound awesome coming into a cruise but the drone on acceleration is killing my ears. The drone is never ending and I wanted to change to corsa or borlas. Let me know how loud the new installs are.
I have Borlas on my 86 and the drone was bad. I made silencers that copied the Corsa design and it worked perfect.
I have a 95 coupe with the axle back Magnaflows which sound awesome coming into a cruise but the drone on acceleration is killing my ears. The drone is never ending and I wanted to change to corsa or borlas. Let me know how loud the new installs are.
I had a set of corsa cat backs on my 96 LT1. not in your face loud, and not so loud as to draw too much attention, but overall, a great sound. best part - no drone.
.. and my husband thought I was the only one crawling on my belly like a reptile with a bottle of simple green, scotch brite pad and a hose in tow under my vehicles!
.. and my husband thought I was the only one crawling on my belly like a reptile with a bottle of simple green, scotch brite pad and a hose in tow under my vehicles!
yeah, but did you ever fall asleep under your car? about 25 years ago, I was restoring my 69 coupe, and one night I was installing the drive shaft, and fell asleep. I worked all day on the job, and worked all evening on the car. it was about 11:00PM - I was on a creeper under the car and the next thing I knew, "lights out." my wife came out at 1:30AM to find me sound asleep under the car. to this day she says i'd rather sleep with the car than her!
- most of my friends think I have a problem. i'd rather spend the day on a creeper, under my car, cleaning and detailing, than playing a round of golf. you try to explain it to them, but they just don't understand. to me, it's mental therapy - I have alone time and i'm in my garage! wrenching on these things is as much fun as driving them. my worst fear is becoming a waxer!
Beautiful job Joe and great write up... For what its worth.... I understand you ! 👍
11-09-2015, 12:53 PM
86-91 exhaust retrofit on my 85 - flowmaster/magnaflow/corsa
- most of my friends think I have a problem. i'd rather spend the day on a creeper, under my car, cleaning and detailing, than playing a round of golf. you try to explain it to them, but they just don't understand. to me, it's mental therapy - I have alone time and i'm in my garage! wrenching on these things is as much fun as driving them. my worst fear is becoming a waxer! 
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Not yet!
