‘87 454 R20 eye watering exhaust w/ windows down

beady · Jul 23, 2024

Hi all, we just bought a really clean 1987 454 R20 with about 80k miles. Driving with the windows down is brutal after accelerating and coming off the gas. Made even worse if the tailgate window is open. Like, so bad your eyes burn and water so badly you can barely see.

It has true dual exhaust on it with tips exiting the back of the truck.

Will kicking the exhaust tips out behind the rear wheels help?

Loving the truck, but it’s rough with the windows down….

Thanks for ideas,

Mike

91burb2500 · Jul 23, 2024

Mine are behind rear wheels, no smell what so ever with only the side windows down. You will get a little blow back if the tailgate window is down due to station wagon effect, but only at slow speeds when the flow from the front vent windows isn’t strong.

Is everything running OK? Not running too rich? Having the exhaust exit rear will make it bad with the tailgate down as there’s nothing to take it away, but with side windows it should be ok unless stopped.

beady · Jul 23, 2024

91burb2500 said:
Mine are behind rear wheels, no smell what so ever with only the side windows down. You will get a little blow back if the tailgate window is down due to station wagon effect, but only at slow speeds when the flow from the front vent windows isn’t strong.

Is everything running OK? Not running too rich? Having the exhaust exit rear will make it bad with the tailgate down as there’s nothing to take it away, but with side windows it should be ok unless stopped.

This was at highway speeds, 60-75. Seems to run well, doesn’t seem to smell excessively rich except after dipping into the gas for a few seconds to pass snd letting up. Got about 10 mpg, so don’t think it’s running massively rich.

But just got it so haven’t really had time to go over it well yet. It’s very clean and been well kept though.

PrairieDrifter · Jul 23, 2024

Pickup or suburban? I also believe side exit behind the tires is best. Suburbans always have that issue. Air just swirls really bad behind them and you will get exhaust smell if you don't have enough front window open. Would not recommend straight out the rear on a suburban.

Pickups shouldn't really have that issue much. I'd say you have en exhaust leak further up, and it's swirling up between the bed and the cab and the settling in the dead spot at the front of the box.

91burb2500 · Jul 23, 2024

beady said:
This was at highway speeds, 60-75. Seems to run well, doesn’t seem to smell excessively rich except after dipping into the gas for a few seconds to pass snd letting up. Got about 10 mpg, so don’t think it’s running massively rich.

But just got it so haven’t really had time to go over it well yet. It’s very clean and been well kept though.

Just need to turn it out the sides then, that will help a lot. Does it have a rear spoiler behind the roof rack? That might make a difference to diffuse the air more, I don’t have one.

beady · Jul 24, 2024

It’s a suburban, not truck. No spoiler, roof rack, anything like that. I was driving with all windows down on interstate, it helped a little bit if I rolled up my driver’s window at the times it got really bad.

Ac doesn’t have enough charge to engage compressor currently, so windows down for now.

We were wanting to tow a horse trailer this weekend, but I’m worried about the horses and the fumes.

fast 99 · Jul 24, 2024

If the exhaust is causing eyes to water, it is due to excess hydrocarbons [HC] unburnt fuel. GM invested a lot of money designing exhaust systems. Using that as a base line [single to dual] is probably the best option. Out the right side behind the rear wheel.

Might be a good idea to have a shop check the actual exhaust content. The engine could have mechanical issues contributing to the exhaust smell.

Is the air pump system and EGR intact and working?

Something has changed since the vehicle was manufactured. GM could never get a vehicle past the gov inspectors like that.

gmbellew · Jul 24, 2024

TotalyHucked · Jul 24, 2024

Yep, the way aero works, the air tumbles behind the truck and brings exhaust into the cabin. Gotta kick the exhaust out the sides behind the tires so it won't do that so bad. I had a K5 Blazer with exhaust like that. Truck ran great, motor was in tip-top shape but it would kill you from the fumes running with the rear window down.

SquareRoot · Jul 24, 2024

Cat. Been there done that. Everyone loves straight pipes and duals until they're sucking on an oxygen bottle to stay alive. Tragedy of the Commons.

Radiohead · Jul 24, 2024

No joke. The last two years at Rod Run in Ilwaco have left me literally breathless down on the gut. I can't run in that much hc/co in the air anymore and it is my own fault abusing my lungs like I have. So now I'm stuck with having to sit in a lot out at the edge of town where the air is considerably clearer. Sit. Not cruising. Sit. A sad irony indeed.

Beach Barons Car Club – Classic Car Rod Run to the End of the World – Ocean Park, WA

beady · Jul 25, 2024

fast 99 said:
Is the air pump system and EGR intact and working?

Thanks for the input everyone. I had a ‘93 gmt400 k2500 until last month and I t had true dual exhaust and the tips exited out to the sides behind the rear wheels and it had no issues with windows down. This ‘87 has issues with the tailgate window up, it’s just worse with it down. Think I need to revamp the exhaust because it’s intolerable at anything over 45 mph right now.

Do the ‘87’s have obd1 I can read codes from? I don’t see any check engine/service engine soon lights to read blink codes from?

Also, where is the stock O2 sensor location, and I’m assuming there was just one singke-wire sensor?

Oh yeah, the air pump looked to be plumbed as originally still and runs when you turn the ignition on. Does it stay running? On my older BMWs it only runs for maybe 30 seconds after start up.

Thanks,

Mike

YakkoWarner · Jul 25, 2024

beady said:
Thanks for the input everyone. I had a ‘93 gmt400 k2500 until last month and I t had true dual exhaust and the tips exited out to the sides behind the rear wheels and it had no issues with windows down. This ‘87 has issues with the tailgate window up, it’s just worse with it down. Think I need to revamp the exhaust because it’s intolerable at anything over 45 mph right now.

Do the ‘87’s have obd1 I can read codes from? I don’t see any check engine/service engine soon lights to read blink codes from?

Also, where is the stock O2 sensor location, and I’m assuming there was just one singke-wire sensor?

Oh yeah, the air pump looked to be plumbed as originally still and runs when you turn the ignition on. Does it stay running? On my older BMWs it only runs for maybe 30 seconds after start up.

Thanks,

Mike

If its a TBI there should be an OBD-1 ECU behind the glovebox (thats where it is on my 1989 Surburban, there doesn't seem to be a lot of major differences between 1987 and 1989 in the ECM systems) and an orange Service Engine Soon light in the speedo. If that doesn't come on when you turn on the key before starting, it may be burned out (or somone got irrritated and took the bulb out). Your computer could be giving you all kinds of clues that you won't even see if the light isn't working.

For what its worth, my 1989 has true duals that exit at a 45 degree angle just aft of the rear wheels, even with all 4 windows down I don't smell any exhaust (I have the ambulance style doors in the back so no tailgate window to open). My O2 sensor is just a single wire unit (and only 1, it doesn't monitor both sides of the engine), I expect yours will be the same. Mine is on the passenger side exhaust manifold just upstream of the pipe flange.

beady · Jul 25, 2024

YakkoWarner said:
If its a TBI there should be an OBD-1 ECU behind the glovebox (thats where it is on my 1989 Surburban, there doesn't seem to be a lot of major differences between 1987 and 1989 in the ECM systems) and an orange Service Engine Soon light in the speedo. If that doesn't come on when you turn on the key before starting, it may be burned out (or somone got irrritated and took the bulb out). Your computer could be giving you all kinds of clues that you won't even see if the light isn't working.

For what its worth, my 1989 has true duals that exit at a 45 degree angle just aft of the rear wheels, even with all 4 windows down I don't smell any exhaust (I have the ambulance style doors in the back so no tailgate window to open). My O2 sensor is just a single wire unit (and only 1, it doesn't monitor both sides of the engine), I expect yours will be the same. Mine is on the passenger side exhaust manifold just upstream of the pipe flange.

So it looks like there might be an overlay on my dash. Is the check engine light behind it? Because I don’t see any cel in the gauge lights.

YakkoWarner · Jul 25, 2024

beady said:
So it looks like there might be an overlay on my dash. Is the check engine light behind it? Because I don’t see any cel in the gauge lights.

I would have expected it to be in the bottom of the speedo, in the left side warning lamp area (but again I have a 1989 so they could have changed it although GM usually kept things pretty consistant). If you can see under the dash, look for a brown wire with white stripe (according to the 1988 and 1989 wiring diagrams its circuit 419, the download on this forum for the 1987 wiring diagram actually gives you the 1988 one). It might just be hanging back there with no bulb, or something else interesting might be going on. I know the 1987 truck my friend Dave had was TBI, I do not know if getting a carb was still an option in 1987 or not - if yours has a quadrajet instead of the TBI than there may not actually be a light and your mixture controls will probably involve adjusting metering jets instead.

‘87 454 R20 eye watering exhaust w/ windows down

beady

Full Access Member

91burb2500

Member

beady

Full Access Member

PrairieDrifter

Full Access Member

91burb2500

Member

beady

Full Access Member

fast 99

Full Access Member

gmbellew

Full Access Member

Attachments

TotalyHucked

Full Access Member

SquareRoot

Full Access Member

Radiohead

That guy on the Columbia

beady

Full Access Member

YakkoWarner

Full Access Member

beady

Full Access Member

Attachments

YakkoWarner

Full Access Member

Similar threads

Latest posts

Forum statistics