No precat y pipe
Thread Starter
Heel & Toe
Joined: Mar 2006
Posts: 21
Likes: 0
From: Greenwood IN
No precat y pipe
Is it worth the trouble to replace the stock (1987) precat y pipe with an aftermarket no precat pipe. I have already installed a high flow main cat (major pain in the ***). I don't want to install headers at this time, but I wouldn't mind a little extra umph.
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
I replaced the precat Y on my 86 with an 85 nocat Y pipe.
The match between the main cat and Y was a problem.
My decision was that gutting the precats created a flow issue thru the cat housing. Also the factory Y is a dual pipe that helps to shield the heat from the floorboards.
I changed the front Y and Magnaflow cat and Borla catback at the same time so its hard to say if the Y was an effective change.
The match between the main cat and Y was a problem.
My decision was that gutting the precats created a flow issue thru the cat housing. Also the factory Y is a dual pipe that helps to shield the heat from the floorboards.
I changed the front Y and Magnaflow cat and Borla catback at the same time so its hard to say if the Y was an effective change.
Race Director
Joined: Aug 2000
Posts: 14,130
Likes: 7
Cruise-In II Veteran
I replaced the precat Y on my 86 with an 85 nocat Y pipe.
The match between the main cat and Y was a problem.
My decision was that gutting the precats created a flow issue thru the cat housing. Also the factory Y is a dual pipe that helps to shield the heat from the floorboards.
I changed the front Y and Magnaflow cat and Borla catback at the same time so its hard to say if the Y was an effective change.
The match between the main cat and Y was a problem.
My decision was that gutting the precats created a flow issue thru the cat housing. Also the factory Y is a dual pipe that helps to shield the heat from the floorboards.
I changed the front Y and Magnaflow cat and Borla catback at the same time so its hard to say if the Y was an effective change.
I bought the catless Y pipe made for my 86 and it bolted in with no hassles or fit problems.
Less heat and the starters lasted longer.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
I had a muffler shop cut off the pre cats and sleeve the pipes. Some shops may not do that. In my case there was a noticable difference in power and sound.
Burning Brakes
Joined: Mar 2002
Posts: 1,035
Likes: 0
From: Atlanta Ga
I just swapped the front Y-pipe and main cat during my L98 rebuild. I picked up a replacement 2 1/2 Y-pipe with no pre-cats and the o2 bung, then mated it to a replacement cat from Mid-America. All fit just like stock.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
I've got a rear Y-pipe with crossover tube on order now, and hope that makes the in car sound better.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
I've got a rear Y-pipe with crossover tube on order now, and hope that makes the in car sound better.
Le Mans Master
Joined: Jul 1999
Posts: 5,005
Likes: 38
From: jackson nj
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Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
[QUOTE=Dolfan;1570467410]I just swapped the front Y-pipe and main cat during my L98 rebuild. I picked up a replacement 2 1/2 Y-pipe with no pre-cats and the o2 bung, then mated it to a replacement cat from Mid-America. All fit just like stock.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
Most likely it is removing the pre cats. I have droan between 1400 and 1700 rpm and did not go to larger Y pipe. The Flowmasters are louder than my mufflers so you probably notice it more.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
Most likely it is removing the pre cats. I have droan between 1400 and 1700 rpm and did not go to larger Y pipe. The Flowmasters are louder than my mufflers so you probably notice it more.
Burning Brakes
Joined: Mar 2002
Posts: 1,035
Likes: 0
From: Atlanta Ga
[QUOTE=BADDUCK;1570468798]
I hope the crossover tube helps a bit
I just swapped the front Y-pipe and main cat during my L98 rebuild. I picked up a replacement 2 1/2 Y-pipe with no pre-cats and the o2 bung, then mated it to a replacement cat from Mid-America. All fit just like stock.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
Most likely it is removing the pre cats. I have droan between 1400 and 1700 rpm and did not go to larger Y pipe. The Flowmasters are louder than my mufflers so you probably notice it more.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
Most likely it is removing the pre cats. I have droan between 1400 and 1700 rpm and did not go to larger Y pipe. The Flowmasters are louder than my mufflers so you probably notice it more.
Safety Car
Joined: Jan 2008
Posts: 3,939
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From: Vero Beach Florida
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
You can always remove the front Y-pipe and "gut" the pre-cats. That way, you don't have to buy anything, don't have to deal with replacing the 02 sensor (which is usually rusted permanently in place), and you wind up with the same effect.
Racer
Joined: Mar 2008
Posts: 254
Likes: 0
From: Perth W.A
Ok can someone please clarify! is the resonator actually a main cat? or just a noise muffler?
the reason i ask is i am thinking about getting a new y front pipe and getting rid of the pre-cats! but in my state we are required to have a cat by law! So if the resonator isn't a cat then it's a fineable offense! not to have one!
i am pretty sure a resonator isn't a cat!
Well it's not considered one on my other cars!
I wouldn't mind just getting two hiflo cats, but rather none if possible!
thanks
the reason i ask is i am thinking about getting a new y front pipe and getting rid of the pre-cats! but in my state we are required to have a cat by law! So if the resonator isn't a cat then it's a fineable offense! not to have one!
i am pretty sure a resonator isn't a cat!
Well it's not considered one on my other cars!
I wouldn't mind just getting two hiflo cats, but rather none if possible!
thanks
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
On the L98 cars, there are two pre-cats and a main cat. The front Y-pipe attaches to the main cat. There is no resonator. A single resonator appeared on the 92 and later LT1 powered cars. Those cars had individual larger single cats just below the exhaust manifolds. From there, each pipe connected to the center resonator.
Does your state have a visual inspection? If so, they may not like not seeing the missing two pre-cats. If you only have to pass an emissions (tailpipe) test, then the single cat at the end of the Y-pipe should work. There are some good high-flow cats that will bolt in and work.
Getting an exhaust shop to install true duals with cats or delete the cats altogether may be hard to do. There is a huge 5-figure fine from the feds if a shop gets caught removing working cats from a car that had them as original equipment.
Does your state have a visual inspection? If so, they may not like not seeing the missing two pre-cats. If you only have to pass an emissions (tailpipe) test, then the single cat at the end of the Y-pipe should work. There are some good high-flow cats that will bolt in and work.
Getting an exhaust shop to install true duals with cats or delete the cats altogether may be hard to do. There is a huge 5-figure fine from the feds if a shop gets caught removing working cats from a car that had them as original equipment.
Burning Brakes
Joined: Nov 2004
Posts: 897
Likes: 12
From: Land of Whiskey Rebels, PA
I just swapped the front Y-pipe and main cat during my L98 rebuild. I picked up a replacement 2 1/2 Y-pipe with no pre-cats and the o2 bung, then mated it to a replacement cat from Mid-America. All fit just like stock.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
I've got a rear Y-pipe with crossover tube on order now, and hope that makes the in car sound better.
One word of caution, I can't be sure which item is responsible but I do have some "Droan" now that I can live without. Not sure if it is due to the 1/4" increased size of the pipe or the pre-cat removal, or combination. This is with Flowmaster mufflers.
I've got a rear Y-pipe with crossover tube on order now, and hope that makes the in car sound better.
I'm interested to see how this works out, especially drone-wise. This is almost the exact setup I am looking at, with the exception of a Random Technology main cat and, maybe, DynoMax High Performance mufflers. The mufflers (2-1/4 inlet), however, are not "carved in stone".
1. Did the front Y come with the O2 bung already welded on?
2. Is the rear Y 2-1/4" or 2-1/2" pipe? (I'm hoping it's the same diameter as the new cat's outlet.)
As you can see, I'm still "doing my homework".
Racer
Joined: Mar 2008
Posts: 254
Likes: 0
From: Perth W.A
On the L98 cars, there are two pre-cats and a main cat. The front Y-pipe attaches to the main cat. There is no resonator. A single resonator appeared on the 92 and later LT1 powered cars. Those cars had individual larger single cats just below the exhaust manifolds. From there, each pipe connected to the center resonator.
Does your state have a visual inspection? If so, they may not like not seeing the missing two pre-cats. If you only have to pass an emissions (tailpipe) test, then the single cat at the end of the Y-pipe should work. There are some good high-flow cats that will bolt in and work.
Getting an exhaust shop to install true duals with cats or delete the cats altogether may be hard to do. There is a huge 5-figure fine from the feds if a shop gets caught removing working cats from a car that had them as original equipment.
Does your state have a visual inspection? If so, they may not like not seeing the missing two pre-cats. If you only have to pass an emissions (tailpipe) test, then the single cat at the end of the Y-pipe should work. There are some good high-flow cats that will bolt in and work.
Getting an exhaust shop to install true duals with cats or delete the cats altogether may be hard to do. There is a huge 5-figure fine from the feds if a shop gets caught removing working cats from a car that had them as original equipment.
I think as long as there is one main cat(the centre one) it should be fine! i am pretty sure our inspections would look for a cat and have an emissions test aswell!
I know there is a huge fine for a shop and myself if found without a cat!
I was told by a fellow vette owner who did this exact modification! pre-cat elim, up to centre cat, then y pipe to mufflers! he said the shop told him it was legal to be rid of the pre-cats!
He gain more torque and that power feeling! and no real drone!
