My dad has an 88 F-250 4x4 with a 351. The cat needs to be replaced and I was wondering which one I should get. The two pipes come off the manifold, and then just before the cat is a square plate. I was thinking about getting a dual inlet, single outlet universal cat and cut off that square plate as it's bolts are rusted pretty bad. Would that work? Also, the air tube connected to the cat broke/rotted off. Would that affect gas milage, it's been really bad lately.

 

Stang,

If you go to a single inlet cat, I am afraid that you will be creating back pressure. Unless you can find a cat with a 3 1/2" single inlet, that would keep you about the same.

The airtube is just for the air pump, it should have nothing to do with fuel mileage. If you look at 90% of older trucks with that setup, I bet the air tube is rusted in two pieces.

My opinion, get a high flow cat with dual inlet and no air tube. Then pull the air injection pump and stuff off the motor and plug where the lines go into the manifolds with pipe plugs. I think they are 3/4" or 1". I don't remember what I was told, but I am facing the same problem.

The only thing with that open air supply is that it might be giving the O2 a false reading. I am not sure on that though.

 

Well I was thinking of getting a dual inlet single outlet...that's what is on there now.

 

You might find a dual inlet/dual outlet cat. My 1990 460 has that, but I am not sure if I am going to replace it or keep it. Not that sure of what I want to do yet with exhaust system.

 

Do you guys know of any direct fit replacements?

 

Go to a local parts shop (not a pep-boys or auto zone) and ask for a direct fit converter for your application. Eastern Manufacturing makes a direct fit for that application.