1 cat or 2 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

orionwy2002 · 02-25-2003, 07:27 PM

I am getting ready to do a drivetrain swap in my 80K10. I'm putting in a 396/700r4/twin stick 205. They just started doing emissions testing around here and I would like to pass so I can register this thing. My questions are:

1) Should I make a Y pipe and run 1 converter with duals or run true duals and 2 converters?
2)If I run true duals with a crossover, where should the cats and the crossover be in relation to the header collectors?

I was thinking that I would not run mufflers at first and see how it sounds. I can always add mufflers later.

I would have a system bent at a shop around here but that means big$$$. My friend with a similiar truck(85K10 406/sm465/205) just had a Y with 1 cat and 2 flowmasters bent from his collectors back and it was $600 for 2.5". It looks like crap and hangs way too low under the truck.

What do you guys think?

LOHRTBT · 02-25-2003, 07:28 PM

NONE!!

Prerunner1982 · 02-25-2003, 07:32 PM

agree with Dave, but in your area you cant do that.. for simplicity purposes i would go with true duals and 2 cats, to avoid the y pipe, trying to route around front drive shaft and such.. hanging low.. just get true duals and have the tuck the up within the frame nicely..

**swervin ervin** · 02-25-2003, 07:40 PM

It just depends on if they'll let you run true duals. I can't where I live. I must have it exactly the way it came from the factory. After the single cat, I can what I like. But, it must be a y-pipe going to a single cat. I asked several different inspectors if I could add another cat and was told no by everyone of them.

So, to sum this up, it depends on what they will let you by with. No nationwide standard on state inspections. It even differs by county in my state.

CustomChevy · 02-25-2003, 07:51 PM

i would forgo cats altogether, not all 80 models had cats. of course, if your state is picky, then you should check your tranny crossmember. if it has one hump, then it didn't have dual exhaust to start with. get a double hump crossmember and run the exhaust.

i would also check another shop to get your exhaust! holy crap $600!!! better be 3" duals all the way in stainless steel.

i can get a true dual setup tucked tight for $150. here. since you're running a k10, you got some lift on it so you could do it yourself. buy a dual exhaust kit with some turbo mufflers or cherry bombs and be done with it. tell inspector, that's the original exhaust it had when you bought it.

good luck!!!

**swervin ervin** · 02-25-2003, 07:59 PM

If it's like it is where I live, it don't matter what you tell the inspector. It will only pass if it's like it was stock. If they get into their computer, it will tell them what it had by the VIN code.

orionwy2002 · 02-26-2003, 12:51 AM

When I bought the truck the PO had put 2.25 single on with 1 cheap muffler and 1 cat so it would pass. I assume that is what it had from factory. I have been told by some that they don't do visual inspection as long as the gas cap works properly and they have tailpipes to put their probes in w/o climbing underneath.

82 Silverado 4X · 02-26-2003, 05:53 PM

We have the same rules here in Pa. as Mike has in N. Carolina. VIN gets punched into the emmisions "anal"izer and it tells the technician what should be on the vehicle.
If you have someone who regularly does your inspections, talk to him before you lay out a bunch $$$. Not much sense in doing it up with duals unless you can get a sticker to be able to drive it.
I have true duals with dual cats on my 82 and haven't had a problem with passing the visual test even though it came with single. The technician who does mine just uses both probes.

PHOENIX · 02-26-2003, 06:02 PM

I say get a single exhuast (3") with one cat. It will save you money, will pass emissions fine, it close to original, and (1) 3" pipe will flow plenty.

Demon of Dreams · 02-26-2003, 06:07 PM

my suggestion would be to run a pair of them... have them right off the headers... if its just sniffer tests you have to pass, having them at the headers will be the most efficient, as the hotter they get the better they work...

if its visual, most shops atleast from my experience don't seem to care as long as they have a cat or cats and pass...

you can do the right thing... and just get cats put on with cheapie mufflers and tips to pass a test, then unbolt both cats and get a different exhaust done

PHOENIX · 02-26-2003, 06:15 PM

Running them any closer then the stock position will ruin your cats. Be careful about the placement, too much heat will ruin them fast!

02-25-2003, 07:27 PM	#1
orionwy2002 Registered User Join Date: Jan 2003 Location: St.Louis Mo Posts: 43	1 cat or 2 I am getting ready to do a drivetrain swap in my 80K10. I'm putting in a 396/700r4/twin stick 205. They just started doing emissions testing around here and I would like to pass so I can register this thing. My questions are: 1) Should I make a Y pipe and run 1 converter with duals or run true duals and 2 converters? 2)If I run true duals with a crossover, where should the cats and the crossover be in relation to the header collectors? I was thinking that I would not run mufflers at first and see how it sounds. I can always add mufflers later. I would have a system bent at a shop around here but that means big$$$. My friend with a similiar truck(85K10 406/sm465/205) just had a Y with 1 cat and 2 flowmasters bent from his collectors back and it was $600 for 2.5". It looks like crap and hangs way too low under the truck. What do you guys think? __________________ Orion 80K10Scottsdale 350/th350/205 d44/14bff locked 35's 97 blazer 4x4 daily driver

02-25-2003, 07:28 PM	#2
LOHRTBT BeWarE tHe eViL CrAnkTOe! Join Date: Oct 2002 Location: Yukon, OK Posts: 3,605	NONE!! __________________ ~Dave~ You can call me Mike, Mike Oxlong - 1986 Chevy SWB - Stock for now - *1986 Chevy Custom SWB* *Stolen 6/26/05* - 1985 Chevy SWB SOLD - 1999 T/A Some mods www.cardomain.com/id/ramairdave AIM Screenname - Jester84

02-25-2003, 07:32 PM	#3
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	agree with Dave, but in your area you cant do that.. for simplicity purposes i would go with true duals and 2 cats, to avoid the y pipe, trying to route around front drive shaft and such.. hanging low.. just get true duals and have the tuck the up within the frame nicely.. __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

02-25-2003, 07:40 PM	#4
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	It just depends on if they'll let you run true duals. I can't where I live. I must have it exactly the way it came from the factory. After the single cat, I can what I like. But, it must be a y-pipe going to a single cat. I asked several different inspectors if I could add another cat and was told no by everyone of them. So, to sum this up, it depends on what they will let you by with. No nationwide standard on state inspections. It even differs by county in my state. __________________ Mike 1985 Chevy C-10

02-25-2003, 07:59 PM	#6
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	If it's like it is where I live, it don't matter what you tell the inspector. It will only pass if it's like it was stock. If they get into their computer, it will tell them what it had by the VIN code. __________________ Mike 1985 Chevy C-10

02-25-2003, 07:51 PM	#5
CustomChevy Registered User Join Date: Nov 2002 Posts: 461	i would forgo cats altogether, not all 80 models had cats. of course, if your state is picky, then you should check your tranny crossmember. if it has one hump, then it didn't have dual exhaust to start with. get a double hump crossmember and run the exhaust. i would also check another shop to get your exhaust! holy crap $600!!! better be 3" duals all the way in stainless steel. i can get a true dual setup tucked tight for $150. here. since you're running a k10, you got some lift on it so you could do it yourself. buy a dual exhaust kit with some turbo mufflers or cherry bombs and be done with it. tell inspector, that's the original exhaust it had when you bought it. good luck!!!

02-26-2003, 12:51 AM	#7
orionwy2002 Registered User Join Date: Jan 2003 Location: St.Louis Mo Posts: 43	When I bought the truck the PO had put 2.25 single on with 1 cheap muffler and 1 cat so it would pass. I assume that is what it had from factory. I have been told by some that they don't do visual inspection as long as the gas cap works properly and they have tailpipes to put their probes in w/o climbing underneath. __________________ Orion 80K10Scottsdale 350/th350/205 d44/14bff locked 35's 97 blazer 4x4 daily driver

02-26-2003, 05:53 PM	#8
82 Silverado 4X Genuine Chevrolet Join Date: Feb 2003 Location: South West Pennsylvania. Posts: 582	We have the same rules here in Pa. as Mike has in N. Carolina. VIN gets punched into the emmisions "anal"izer and it tells the technician what should be on the vehicle. If you have someone who regularly does your inspections, talk to him before you lay out a bunch $$$. Not much sense in doing it up with duals unless you can get a sticker to be able to drive it. I have true duals with dual cats on my 82 and haven't had a problem with passing the visual test even though it came with single. The technician who does mine just uses both probes. __________________ George 82 Silverado LWB 4x4 350 SM465 NP208 77 Chevrolet Blazer Chalet 400 TH350 NP203

02-26-2003, 06:02 PM	#9
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	I say get a single exhuast (3") with one cat. It will save you money, will pass emissions fine, it close to original, and (1) 3" pipe will flow plenty. __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

02-26-2003, 06:07 PM	#10
Demon of Dreams WEEE!!! Join Date: Feb 2003 Location: Salem, OR Posts: 73	my suggestion would be to run a pair of them... have them right off the headers... if its just sniffer tests you have to pass, having them at the headers will be the most efficient, as the hotter they get the better they work... if its visual, most shops atleast from my experience don't seem to care as long as they have a cat or cats and pass... you can do the right thing... and just get cats put on with cheapie mufflers and tips to pass a test, then unbolt both cats and get a different exhaust done

02-26-2003, 06:15 PM	#11
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	Running them any closer then the stock position will ruin your cats. Be careful about the placement, too much heat will ruin them fast! __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

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