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Exhaust setup

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Old May 25, 2024 | 03:07 PM
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Exhaust setup

I have a 1990 f350 5.8 that’s in need of a cat due to someone stealing mine. They cut above the cat and below. I want to replace it with a used factory cat. I found someone with a 7.5 f450 that looks like it has the same exhaust setup. Does anyone know if the entire exhaust system for a 7.5 f 450 will bolt up to my 5.8?
 
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Old May 25, 2024 | 05:12 PM
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The H-pipe is different between a 5.8L and 7.5L engines. Also has different routing for a manual versus auto transmission. Same 4 bolt converter flange.
 
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Old May 25, 2024 | 07:41 PM
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Originally Posted by rla2005
The H-pipe is different between a 5.8L and 7.5L engines. Also has different routing for a manual versus auto transmission. Same 4 bolt converter flange.
do you know what the other pipes coming off the cat are and if they match a 5.8? The thief’s cut those and I don’t think I’m going to pass smog without them. I’m assuming it’s some sort of o2/ egr setup. I can just take the new and cut with both flanges and weld that up. My biggest concern is those other pipes. I appreciate your help!
 
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Old May 25, 2024 | 08:07 PM
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Don't the other pipes come from the air injection/thermactor/"smog pump"?
 
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Old May 25, 2024 | 08:12 PM
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Originally Posted by rla2005
The H-pipe is different between a 5.8L and 7.5L engines. Also has different routing for a manual versus auto transmission. Same 4 bolt converter flange.
Originally Posted by 85e150
Don't the other pipes come from the air injection/thermactor/"smog pump"?
Is that what that’s for? I’m not sure. There’s 2 lines though. I’m thinking one is EGR and other must be smog pump then.
 
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Old May 25, 2024 | 08:20 PM
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Both pipes are part of the air injection system. EGR port is on the passenger side exhaust manifold.
 
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Old May 25, 2024 | 09:40 PM
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Why not do aftermarket DI/SO cat? They are worth less on black market.
 
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Old May 26, 2024 | 12:51 AM
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Originally Posted by rla2005
Both pipes are part of the air injection system. EGR port is on the passenger side exhaust manifold.
so those pipes aren’t important for smog?
 
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Old May 26, 2024 | 12:52 AM
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Originally Posted by Hit Man X
Why not do aftermarket DI/SO cat? They are worth less on black market.
DI/SO cat? I’m in California so it has to be stock or carb compliant.
 
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Old May 26, 2024 | 06:02 AM
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Originally Posted by wyattstarrF350
so those pipes aren’t important for smog?
That is part of the emissions control

Originally Posted by wyattstarrF350
DI/SO cat? I’m in California so it has to be stock or carb compliant.
In that case, you will have to have the air injection system
 
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Old May 26, 2024 | 10:38 AM
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7.5L utilized a single 3"in/out catalyst. Not a 'stacked' twin-pipe in/single out like a 5.8L
 
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Old May 26, 2024 | 12:24 PM
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Thought they had dual head pipes into some square flange and a single pipe out?

Do you need just the CARB number on the catalyst? A stocker will be expensive.
 
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Old May 26, 2024 | 01:19 PM
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Pic 1

 
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Old May 26, 2024 | 01:20 PM
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Pic 2

 
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Old May 26, 2024 | 01:21 PM
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Pic 3

Silver pipe on the left edge is the start of the catalyst . Mine was stolen as well, and the new one welded in place

 
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