my cats are red!!!!
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 1,235
Likes: 0
From: Mesa AZ
my cats are red!!!!
i just got a edelbrock 750 on my 75 l48. i tuned it and took it for a couple of test drives. then i started seeing smoke that seemed to be comming from around the trans and then i started to smell fiberglass. it didn't seem that odd because i was sanding my car and maybe i just got some dust in the vents. then a lot of smoke stated to come up around the car and the tail pipes were really hot. so i looked underneath and was shocked. the catalytic converters were molten red. 
at first i thought those $30 pieces of s*** were clogged, but there seemed to be good flow from the tail pipes.
i've read some posts on how a car running rich has hotter exhaust, so i tightened the mixture screws and they cooled right down.
so my car still smells like melting fiberglass and i have a c.d changer remote that sits almost directly above one of the cats and it MELTED into my carpet.
but everything is good know. shes running beautiful
at first i thought those $30 pieces of s*** were clogged, but there seemed to be good flow from the tail pipes.
i've read some posts on how a car running rich has hotter exhaust, so i tightened the mixture screws and they cooled right down.
so my car still smells like melting fiberglass and i have a c.d changer remote that sits almost directly above one of the cats and it MELTED into my carpet.
but everything is good know. shes running beautiful
Melting Slicks
Joined: May 2004
Posts: 2,501
Likes: 510
From: Willowbrook IL
St. Jude Donor '13-'14-'15-'16
Originally Posted by Pete76Shark
If you want to cool down the exhaust temp you richen the mixture.
If you want to raise the exhaust temp you lean the mixture.
More gas = cooler exhaust temp.
If you want to raise the exhaust temp you lean the mixture.
More gas = cooler exhaust temp.
But with the very rich exhaust, the unburnt fuel is burnt in the catalytic perverter. That can get the cats to over 2000 F. That IS hot enough to melt the ceramic part of the converter.
Don
Le Mans Master
Joined: Oct 2004
Posts: 5,269
Likes: 54
From: Orlando Florida
St. Jude Donor '05
If it melted your CD changer it very likely melted the ceramic perverter internals also..... that would explain why she runs great and why there's a lot of flow at the tailpipes... 
hollow converter = good converter
hollow converter = good converter
Racer
Joined: Jan 2005
Posts: 492
Likes: 0
From: Birmingham AL
Originally Posted by chris75stingray
so my car still smells like melting fiberglass and i have a c.d changer remote that sits almost directly above one of the cats and it MELTED into my carpet.
but everything is good know. shes running beautiful
but everything is good know. shes running beautiful
Remove the Cats!
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Verdad Gallardo
Safety Car
Joined: Oct 1999
Posts: 4,101
Likes: 10
From: NorCal
Originally Posted by Pete76Shark
If you want to cool down the exhaust temp you richen the mixture.
If you want to raise the exhaust temp you lean the mixture.
More gas = cooler exhaust temp.
If you want to raise the exhaust temp you lean the mixture.
More gas = cooler exhaust temp.
I see this a lot with early Catalyst controlled vehicles that are modified. You mentioned an upcoming smog test, so your best bet is to get it pre-tested. That accomplishes a couple of things. First, it'll let you know if your cat (s) survived, which is a possibility, and you can fine-tune your mixture to (a) pass smog, and (b) not smoke your converter.
Even then, make sure your EGR valve works if you do any mountain driving, because a long pull up a grade will cause a rich mixture at a lower RPM (thus overheating the cat), and a good EGR adds burned (inert) gas to the intake charge, reducing the amount of total air/fuel volume in the cylinder and reducing the resulting cylinder/exhaust temps. Most replacement GM EGR valves come with a variety of orifices that apply to different calibrations, but I like to experiment with smaller discs to get good power while still meeting emmisions. That's critical here in CA where they check for Nox on a dyno, and they won't pass without the EGR working.
Get this resolved, or you run the risk of melting more than just a little carpet.
Hans
Instructor
Joined: Jan 2003
Posts: 179
Likes: 0
From: Burlington Ontario
Originally Posted by vetsvette2002
Exhaust gas temp yes.
But with the very rich exhaust, the unburnt fuel is burnt in the catalytic perverter. That can get the cats to over 2000 F. That IS hot enough to melt the ceramic part of the converter.
Don
But with the very rich exhaust, the unburnt fuel is burnt in the catalytic perverter. That can get the cats to over 2000 F. That IS hot enough to melt the ceramic part of the converter.
Don
Good Luck
Melting Slicks
Joined: May 2001
Posts: 2,131
Likes: 4
From: May help you? You can sure as hell try!
Had an old van that the cat started to rattle on. A couple of well placed deck screws through the case and into the ceramic brick solved the problem without replacing the cat.
Best of luck,
Bubba
Best of luck,
Bubba
Team Owner
Joined: May 2001
Posts: 29,745
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From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Originally Posted by Pete76Shark
If you want to cool down the exhaust temp you richen the mixture.
If you want to raise the exhaust temp you lean the mixture.
More gas = cooler exhaust temp.
If you want to raise the exhaust temp you lean the mixture.
More gas = cooler exhaust temp.
the extra fuel will first clog the cats, and then the cats act as afterburners. The additional fuel gets burned in the cats making them hotter and hotter. Cats have been known to burst, interiors can catch fire other similar problems. Also, never pull over to the side of the road and park over dry grass. The cats can cause the grass to catch fire and then your car will become a fiberglass puddle on the side of the road.
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 1,235
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From: Mesa AZ
i'm lucky i caught that before anything caught fire. i had to take the EGR off because it interfered with the carb linkage, but its next on my list to put back on.
emissions aren't untill june, but it was way below the standards last year so i think it will pass even w/o cats.
emissions aren't untill june, but it was way below the standards last year so i think it will pass even w/o cats.
Team Owner
Joined: Jan 2002
Posts: 120,798
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From: Charlotte NC
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Originally Posted by flood
wow what a mod. Just richen the hell out of your carb and burn the cats straight thru. Emissions guys are happy cause you got cats and your happy cause there ain't nothin in em! win win 
Team Owner
Joined: May 2001
Posts: 29,745
Likes: 3
From: Exiled to Richmond, VA - Finally sold my house in Murfreesboro, TN ?? Corner of "Bumf*&k and 'You've got a purdy mouth'."
CI 6-7-8 Veteran
CI-VIII Burnout Champ
St. Jude Donor '06-'10, '13
Originally Posted by chris75stingray
i'm lucky i caught that before anything caught fire. i had to take the EGR off because it interfered with the carb linkage, but its next on my list to put back on.
Uhhh -- you did put a plate to block off the hole, right ?
And it does have a gasket, and all is tight ??