My cat is starting to go bad so i found a couple of high flow cats on ebay for less than $50 made by Carsound (makers of Magnaflow) I called an exhaust shop and they said that i had to put the big one on for $450 (direct replacement) because the universal ones are too small, but then he contradicted himself by saying that Ford was the only one that put these monster cats on. (if nobody else needs this huge cat, then why does my Ford?)I'm thinking about putting the universal cat on with a short extension pipe to make up the length and go from there. My truck has Gibson headers and a 3" Magnaflow cat-back system (single into duals). Am I going to be fine with this setup or do I need to spend 10 times the money and get the big one? Thanks for the advice, Tim

p.s. this is on a 94 f350 crewcab 4x4 with 460 and auto tranny, lifted with 38" swampers, daily driver.

 

Define "large" and "small" ?

To indirectly offer an opinion:

I'm thinking you could run *true* duals, come out cheaper by using the "small" cats, and get better over all performance.
Of course, this must be qualified to work:

My suggestion is this, each header dumps into it's own cat - those cats have no less than 2 1/2" in AND out. Preferably, 2 3/4" with 3" a maximum. They each continue on out the back after passing through a magnaflow muffler (unless you just like the bone jarring sound of flowmasters) and terminate in ~3" tips. Preferably, between 10 and 12" long.

Now . . if I had more information, I could probably be specific

 

My factory cat (Large) is 30 inches end to end, (the cat portion is 24" not including the pipe on the ends) The aftermarket cat (Small) is considerably shorter, i'm guessing 12-15 inches. I already have the 3" single to dual Magnaflow catback as it came on the truck when i bought it, and I recently put on the Gibson headers. I really don't want to spend the $450 for anything right now, the catback is almost new, and the headers are brand new, I just want to replace my cat without breaking the bank. I do like the bone jarring sound of Flowmaster as I have them on my mustang gt and my wife's expedition, but since the crew already has the Magnaflow, i'm sticking with it. The header collector to the muffler is 3" and the duals out of the muffler are 2 1/2", then it has tips that are 4" x 22" long coming out behind the rear tires at an angle. Thanks for your advice. Do you think the universal high flow cat will work in place of the factory unit? Thanks, Tim

 

Because of the weight of the truck and the flow that your 460 puts out, if you put the small cat on it's gonna melt withing the first 3 months. The only way around the big cat is 2 cats with duals.

Now if your gonna spend 450 on one cat and still have the same thing, I would look at spending 450 on 2 front pipes 2 cats and 2 mufflers. Might as well go all th eway if your gonna do it right???

 

my advice is if there is no emissions loose the cats and go dual flowmasters

 

If you don't have emsissions testing get ride of the cat and save yourself $450. If you have just a visual inspection just gut the cat out so it still apears to have one on it.

 

Well I went to my local exhaust shop and got 6 feet of 3 inch pipe for $12 and took out the cat, WOW what a difference, now I finally get to enjoy the sounds of my Gibson headers and Magnaflow exhaust, I love it. Screw emissions!!! Thanks for all the advice, I should have just went with my instincts to begin with. Thanks again, Tim

 

How did your truck sound with the Magnaflow (with the stock cat). What were the differences.
I asked because I need a muffler and I was thinkin about an aftermarket free-er flowing muffler.

 

it had a really good sound, but very quiet in comparison to most, after i got rid of the cat and put a straight pipe in it's place, it made it rather loud. I like it, but some would think it was too loud. before i put on the headers and it only had the magnaflow catback, (single in, dual out) it was very quiet, not as quiet as stock, but not very noticeable either. when i added the headers it helped the sound a little, then when i got rid of my cat, it made a huge difference in sound. keep in mind that my cat was starting to go bad, so it might have been restricting the sound a little. most people recommend true duals, but since mine had the single to dual when i bought it, and it is almost new, I decided to stick with it. With gibson headers, no cat, and single to dual magnaflow, I'm VERY happy, but I do think it's a little loud for some. hope this helps, Tim

 

Glad you like it now. 460's sound great when you let them breath a little. I ran mine with a single 3' strait pipe for a little while before I got the headers and exhaust done and that was very loud but fun.

 

Yes, I'm very happy now. speaking of breathing, can anyone recommend a good set of heads that won't break the bank, I'm also looking for a cam, but I know I need to do a lot of research for the cam selection since it's a big truck and I tow a travel trailer several times a year. Thanks again, Tim

 

DOn't forget about the air intake system also. A good cold air intake from K&N will go a long way to improving power as well

 

The K&N is in the mail as we speak...

 

As for the heads you are stuck with porting the factory ones unless you get a set of pre EFI heads and a carb intake then have injector bugs welded in. This would be quite expensive and most likely not worth it. Check your spark plugs to make sure the engine isn't running to lean. My truck leaned out and goes through plugs quite fast. I have an adujustible fuel pressure regulater on the way to fix that problem though. Hope this helps some more

 

ya without the cats the sound is more burbely at the tips instead of just loud