Pulling all the smog stuff

[PhotonFanatic]

I heard that back in the 1980's people would remove all the smog stuff from their trucks. I have an 87 with the TBI 350, so here's my questions:

1. They said the trucks would run better after that. Is this true?

2. What exactly do they mean by "run better"? Is it smoother, less noisy, or just have more power?

3. Can I just cut the belt on the smog pump, or is that a bad idea?

4. Will the truck smell terrible at idle if I remove all the smog stuff?

5. Will the check engine light come on? Any other considerations like that?

6. How many block-off plates will I need if I remove the whole smog apparatus? (everything including all that tubing and whatnot that runs along both sides of the engine)

Thanks!

 

[DoubleDingo]

Run better, no. Maybe less parasitic horsepower loss with the parts removed. Why not just remove the belt instead of cut it? The truck will probably smell the same. I don't know about the check engine light, someone will chime in on that. Also not sure about the amount of block off plates.

 

[sidschev]

i think your TBI requires it for fuel adjustments. computer controlled i believe......

 

[DoubleDingo]

i think your TBI requires it for fuel adjustments. computer controlled i believe......

Oh yeah, TBI, I didn't pay attention to that

 

[82sbshortbed]

I have headers and no smog crap on both my squares. 305 and 454 both carburetors and dual exhaust with no cats. No tbi but they're also a 82 and 84 year models. I think they run much better without it choking the exhaust. A huge difference probably not but enough for me to remove it because TX doesn't require it.

That being said I'm not sure on the effects on the tbi. It may not effect it but I'm not sure. Think if you remove the belt to the smog pump you'll gain a little hp too. Not a ton but every little bit helps. Lol

Imo if you remove all that stuff I'd go back with headers and you'll even gain a little more hp. I'm not sure if that's what you're looking for is more hp but it will help with that imo.

 

[justhorns]

One thing to watch out for- If your catalyst gets a load of rich mixture, It will burn up and melt. The melting blocks your exhaust and you will lose massive power. The smog pump adds air to the exhaust to complete combustion in the manifolds and partially prevents this. So, pulling all the emission stuff should include removing the catalysts.

 

[fast 99]

Air pump is there to preheat the cat and O2. EGR lowers combustion temperatures reducing NOX. O2 sensor provides fine tuning data for fuel mix. MAP provides intake HG to calculate load and mix during warm up through an algorithm in the ECM. After warming up, combination of the 2 inputs data for fuel trim.

No, you can't just yank these items off without a fuel millage decrease or creating drivability issues. First problem is the O2 and cat will become contaminated. Cat may plug up or melt down. O2 will not provide feedback to ECM. ECM will stay in open loop, in other words rich. Removing EGR may create a ping or knock. Removing air pump will extend warm up cycle.

What are you trying to accomplish?

Yes, the check engine light will come on. TBI systems are very basic, dependable, fairly economical, and very reliable. Given choice of a carb or TBI,? I would take TBI every time and I know how to fix Q jets.

 

[PhotonFanatic]

I've also heard that the cat will get glowing hot. Not sure about that one though.

I was just trying to accomplish a cleaner engine bay and to pick up whatever small amount of power could be had. But it sounds like all that stuff needs to stay there. I'll rely on a 5.3L to delete it.

 

[sidschev]

convert to carb problem solved

 

[Dixie Pride]

My 85 K20 350 engine is not fuel injected.I had a shop de-smog mine. I had taken the converter off years and went to dual exaust.The shop removed the smog pump and everthing it went to.There is one place in the engine that has to be plugged.My engine looks clean now runs better in my mind than it did before and there was no engine adjustments required,dont know what changes an 87 had compared an 85.

 

[1lejohn]

What others have stated if it was a carb you can pull most of the smog junk. If it's TBI I wouldn't. You could remove the cat then you can remove the air pump . My 85 had a cat with an air pump, heat riser, EGR and EST. The cat was removed when I bought it along with the other junk. Being in Texas you could remove the heat riser and EGR along with the cat and air pump. Doing so would generate trouble codes.

 

[andybflo]

Well...

If your goal is to LS swap it, why bother? Just run the thing.

The early GM TBI runs really well out of the box. Before performance EFI was a more DIY thing, I used a *lot* of GM TBI setups on restomod cars, they'll run relatively maintenance free for 100k miles, without issue. Regarding mid-80s smog and Cats? They figured the systems out by then. Your parasitic loss and exhaust restrictions are probably less than 5hp; keep it in tune and she'll run great.

Regarding long term use of Cats? I live in NY; my '86 is cat-exempt. There are 2 2.5" Flowmaster high-flow cats on there, with the LS Swap (upstream O2 only.) I've *added* cats (and a ton of heat shields to not melt the floor) to my LS7-swapped '69 Corvette. I'll be adding cats to my '73 455-powered GMC Motorhome (Holley EFI.) And I plan to with my '63 Stroked-409 powered Impala (Running Holley EFI) when the frame comes off. My '67 Citroen is the only car I have no plans to run a Cat on, because... I just frankly don't know why or how it would be of benefit.

I'm far from a treehugger (the Square gets the best fuel economy of the above), I fly airplanes that burn leaded fuel, owned big-block powered boats for ripping around the great lakes, drive bad stuff.

I guess I have two thoughts... I've reached an age where I don't want to get out of my car smelling like unburnt 93 anymore. I own a drag car; it's fine there. Driving my wife for a dinner in the Corvette, why? Second, just because you *can* blow a ton of hydrocarbons into the environment doesn't mean you *should.* I look at this hobby as something I want to pass down to my kids; if I contribute a little to keeping the air cleaner, maybe I can... We install them (and encourage it for the above reasons) on almost every restomod we ship. That TBI rig gets you simplicity, and 90% of the EFI benefits of a modern OBDII car. Including better fuel metering/monitoring.

Modern cats offer virtually zero horsepower loss (I can prove that on a dyno, btw) on a properly sized exhaust. They weigh almost nothing. Unless the $150/ea is an insurmountable hurdle, why not just run 'em?

 

[GTX63]

I heard that back in the 1980's people would remove all the smog stuff from their trucks. I have an 87 with the TBI 350, so here's my questions:

1. They said the trucks would run better after that. Is this true?

Depended on the truck.

2. What exactly do they mean by "run better"? Is it smoother, less noisy, or just have more power?

Sometimes less noisy, maybe a bit more pep.

3. Can I just cut the belt on the smog pump, or is that a bad idea?

4. Will the truck smell terrible at idle if I remove all the smog stuff?

Pre catalytic converter, it didn't make an iota of difference.

5. Will the check engine light come on? Any other considerations like that?

The computer on a 1987 is pretty simple minded. They didn't store many trouble codes .

6. How many block-off plates will I need if I remove the whole smog apparatus? (everything including all that tubing and whatnot that runs along both sides of the engine)

I just had a heck of a time trying to locate a block off plate for an odd sized EGR on an 83 K10. I ended up making my own.

Thanks!

Most guys back then pulled the smog equipment when it started to malfunction, when they changed out a motor, or when they just didn't like Uncle Sam trying to design their engines. If you notice some better performance, it was usually only slight, or imagined. The cylinder heads of the 80s were the biggest culprit to killing horsepower.

 

[SquareRoot]

Well...

If your goal is to LS swap it, why bother? Just run the thing.

The early GM TBI runs really well out of the box. Before performance EFI was a more DIY thing, I used a *lot* of GM TBI setups on restomod cars, they'll run relatively maintenance free for 100k miles, without issue. Regarding mid-80s smog and Cats? They figured the systems out by then. Your parasitic loss and exhaust restrictions are probably less than 5hp; keep it in tune and she'll run great.

Regarding long term use of Cats? I live in NY; my '86 is cat-exempt. There are 2 2.5" Flowmaster high-flow cats on there, with the LS Swap (upstream O2 only.) I've *added* cats (and a ton of heat shields to not melt the floor) to my LS7-swapped '69 Corvette. I'll be adding cats to my '73 455-powered GMC Motorhome (Holley EFI.) And I plan to with my '63 Stroked-409 powered Impala (Running Holley EFI) when the frame comes off. My '67 Citroen is the only car I have no plans to run a Cat on, because... I just frankly don't know why or how it would be of benefit.

I'm far from a treehugger (the Square gets the best fuel economy of the above), I fly airplanes that burn leaded fuel, owned big-block powered boats for ripping around the great lakes, drive bad stuff.

I guess I have two thoughts... I've reached an age where I don't want to get out of my car smelling like unburnt 93 anymore. I own a drag car; it's fine there. Driving my wife for a dinner in the Corvette, why? Second, just because you *can* blow a ton of hydrocarbons into the environment doesn't mean you *should.* I look at this hobby as something I want to pass down to my kids; if I contribute a little to keeping the air cleaner, maybe I can... We install them (and encourage it for the above reasons) on almost every restomod we ship. That TBI rig gets you simplicity, and 90% of the EFI benefits of a modern OBDII car. Including better fuel metering/monitoring.

Modern cats offer virtually zero horsepower loss (I can prove that on a dyno, btw) on a properly sized exhaust. They weigh almost nothing. Unless the $150/ea is an insurmountable hurdle, why not just run 'em?

WELL PUT! I had the same experience. There's even a long contentious thread called "Bringing back the cats, enough is enough". I run a magnaflow hi-flow cat with zero loss in power and enjoy not breathing poisonous gas.

 

[Redfish]

My 1987 had been butchered a little bit so I can probably give you some decent input on this.

1. You can just removed the drive belt from the pump IF you no longer have the catalytic convertor.

2. If you have removed the cat and you still have air getting into the exhaust you now have a problem. That oxygen will cause back firing. Unless you plug the tubing in some way you will continue to get oxygen into the exhaust even if you have removed the drive belt. I cannot stress that you WILL have back firing and it will be significant, it will be loud, and you cannot operate the truck in any way that prevents it. Mine sounded like a 12 gauge shotgun every time I shifted until the engine warmed up. Gearing down while decelerating was awful. I finally found an easy way to plug the tubing and my dual Magnaflows now sound pretty nice.

3. The PO removed that belt AND removed the vacuum line to the EGR Valve so it no longer functions. If I drive around town and don't push the truck hard I never get a Check Engine light. If I get on the interstate I get a Check Engine light within the first 10 miles. It doesn't store that code so I don't know what it is.

If you decide to swap out the TBI please sell me the vacuum lines that are associated with the EGR Valve. If you still have that heat riser, I will happily buy that as well.