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Desmog 1990 7.5L EFI

8K views 13 replies 5 participants last post by  ValkyrieJosh 
#1 · (Edited)
I have a 1990 F-350, 7.5L EFI. Recently discovered performance issues due to a bad catalytic converter. Being an old truck and not having smog testing where I am, I am going to delete the cat.

This causes a problem with the 2 smog lines that connect to the cat, so..

..I'm considering doing a desmog removing the air pump, canisters, etc, etc. I will leave the EGR Valve intact. I know I will have to get a new belt to drive the alternator, but is there anything else I need to consider or any words of wisdom you can offer before I go about this?

I thank you in advance for your replies.
 
#2 ·
Wow, not one response or reply. I belong to other forums and this is a first.

Anyway, I did the desmog. It took a couple of hours and was pretty straight forward. I left the first charcoal canister, and removed the 2nd. Only had to plug one vacuum line to the EGR Valve. The new alternator belt is 3" shorter than stock.

I took the truck to my exhaust guy who did a 3" exhaust with a MagnaFlow muffler from the Cat flange back. It took both of us to remove the old muffler. It must have had a hundred pounds of carbon built up in it. The muffler alone probably weighed over a hundred pounds.

Hoping for more from this forum in the future.
 
#5 ·
Wow, not one response or reply. I belong to other forums and this is a first.

Anyway, I did the desmog. It took a couple of hours and was pretty straight forward. I left the first charcoal canister, and removed the 2nd. Only had to plug one vacuum line to the EGR Valve. The new alternator belt is 3" shorter than stock.

I took the truck to my exhaust guy who did a 3" exhaust with a MagnaFlow muffler from the Cat flange back. It took both of us to remove the old muffler. It must have had a hundred pounds of carbon built up in it. The muffler alone probably weighed over a hundred pounds.

Hoping for more from this forum in the future.

This is why I gave that response...


SJ
used 2b RHP



:D
 
#3 ·
Disabling the EGR can bring on light throttle ping if the timing tables are not changed to reflect the need for less part throttle timing with out EGR.



SJ
used 2b RHP


:D
 
#6 ·
Hey valkyriejosh I’m putting new banks torque tube headers on my 94 F-250 and noticed my new headers only have one hole for the EGR as to where the stock manifold has two EGR and air pump. I’ve decided to do away with the air pump opposed to waiting for banks to make me a new left side header. Not a whole lot of info on that subject here. I was just curious, did you notice any performance or any type of change when you did yours? Thanks.
 
#7 ·
Dino85,

I did a desmog, as well as a Cat delete, and 3" exhaust with a small muffler. Did I notice any performance!? Yes! Not night and day, but the throttle response has greatly improved. Over the last 10 years of owning the truck it as gotten 9-10mpg. I recently did a 200 mile drive, towing a bike up to a buddies house. The truck got 11.4mpg. That's a 12% increase in fuel economy while towing. Not bad. I'm happy with the mods I have made. Hope you have similar results, let me know.
 
#8 ·
I cut the air horns (restrictors) off of the plastic junction between the rubber air intake hoses, upped the fuel pressure with an adjustable fuel pressure regulator and a mild 204/214 cam.
Pulled 26,000# of pulling trucks 'till I got the Powerstroke.
 
#9 ·
I too have cut the Air Horns. This makes me think..

The desmog, and cutting the Air Horns was easy. The new 3" exhaust was affordable.

I think Heads would have to be my next upgrade, but what else can easily be done to my highly restrictive 7.5L/460ci V8 to produce more than 234 horsepower?
 
#12 ·
Dino85,
I did a desmog, as well as a Cat delete, and 3" exhaust with a small muffler. Did I notice any performance!? Yes! Not night and day, but the throttle response has greatly improved. Over the last 10 years of owning the truck it as gotten 9-10mpg. I recently did a 200 mile drive, towing a bike up to a buddies house. The truck got 11.4mpg. That's a 12% increase in fuel economy while towing. Not bad. I'm happy with the mods I have made. Hope you have similar results, let me know.




I just finished up with mine last night, got a little side barred away from my project for a few days, $h!t happens.
Good news is the metal air line that once was connected to my header is in the bed of the truck! Definitely a noticeable difference...could be the new headers helping out in that difference too lol. Only one hucup which I’m about to go check out once I submit this is my truck is idling more than rather high (1500rpm) it idled high before (1100-1200rpm) I figured that was caused from the old exhaust manifold that was leaking and figured it would drop after this....well I was wrong! I’m thinking of there may be a vacuum leak somewhere, that’s where I’m going to start anyway.

And as far as more performance adds, this is where I’m at thus far. Obviously did away with air smog pump and installed new headers, 3” exhaust with cat removed (no inspections in Florida!) to a dynomax muffler, K&N filter & air horns cut out, upped fuel pressure via adjustable pressure regulator made by aeromotive, 180* thermostat and I bumped my timing up to about 13-14 from 10 BTDC. Once I get my rpm’s to drop I’m going to rock it like this for a bit, allow my bank to build back up and then I’ll be looking into getting some good headwork done along with an efi cam and new intake. Parkland performance Auto Machine is where I’ll be going for those mentioned mods.
 
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