The cats in my 01 5.4 are starting to rattle. It has the twin cats for each bank. I was wondering if anyone has replaced theirs with a single high flow and if it's kept the down stream o2 sensors happy?

 

I just cut out my rear ones and added in Maggie high-flows. Kept the front cats. Fits perfect and O2s are happy. It even helped out my gas mileage and deepened the idle.

 

I took out all 4 and replaced the with single maggie hiflows. O2's are happy, etest #'s went up a little but passed. Keep your old cats when you cut them, take em to a scrap metal dealer and get some $$ for them.

 

Yes and it's the rears you have to keep happy. If you not going headers, - OFF the rear converters, but keep it tight. You'll know if it's not tight ENOUGH with a CEL.

If your going headers, attach HF's to the collectors. 4WD's have to,- in order for the cross over to line up.

 

Also, if your not going headers, you can do it this way. - Gut your forwards and run a High Flow behind. If your going to have a shop run turn downs for just one high flow connect, you might as well run headers, - money wise anyway.

That's because you can net around $200 for Ford factories and find headers (LT's) for as cheap as $300. High Flows for maybe $160.

No tune needed for headers alone.

 

An even cheaper way to get rid of the rattle. Follow the Ford TSB and use band clamps. I have the correct band clamp number sizes posted on this site somewhere.
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One other way is to rip the heat shields off the cats. Since a spot weld broke and that's why they rattle most of the time.

BTW- I've done every mod I just listed, before eventually just going with headers.

 

I'll do a search for the band clamps.

Wasn't looking to do headders, the manifolds are still holding in there and I'm not out for every hp I can squeeze from the truck just the rattle is annyoing and I figure $100 a pop for high flows as opposed to 500-600 for a new y-pipe is easier to handle. I know the downstreams just monitor the cat's essentially just wanted to hear from a few people if there where many issues with CEL's

 

For $400-$500 you can buy the whole piping assembly from Magnaflow. Direct bolt-in from the headers to the muffer. Includes four O2 bung holes and Maganflow pre-cats and main cats welded in.



I should've gone this route. I spend $150 for two main cats and $150 to have them welded in. For another $100 more I could've got the whole damn package.

 

Sorry to butt in,will that magnaflow bolt up to the factory manifold?

 

^yes get the one with the right size pipe diameter.

Just a note magnaflow hi-flows are only around $55 each. At least they were when I looked at them a while back.

 

The Magnaflow set up in the pic, Rapter has a pic of ? That's half of a direct fit package, very expensive like he said, 400 - 500 bucks.

 

what cats are yall using to repalce the rear cats..could you include a part number ill be ordering some soon

 

how dose it sound with the rears replaced raptor?

 

Part numbers are in the exhaust forum. I used these -

 

Ahhhhh, crap! I've got a rattle that developed a month or so ago on mine that I cannot find!!!! You can hear it like when you're beside another car or beside a wall, like a bridge or something. Only does it about 35mph+. I bet this is what I've got going on too.