Been driving the heck out of the 96 F150 I picked up and it seems like the catalytic converter(s) are not so good. The exhaust stinks and it feels like the engine struggles to breathe a bit at highway speeds. Highway speed between here and the deer lease is ~80 mph. A better breathing exhaust has got to help.

I've got a 3" converter sitting around, so I'm thinking about a single 3" exhaust. I had a similar system on the 302 in my old F250 (sans converter) and it worked well. Anyone running a 3" single on their 300?

 

I have EFI exhaust manifolds, a custom Y-pipe and a single 3" stock muffler (no cat) on my son's 72 F-100 with a 300/6. The P/O put a cam, Offy C intake and Holley 390 on the truck.

 

Sweet, I ordered a giant 30" long Magnaflow straight-through muffler to go behind that 3" 3-way converter I had in the shed. Should free up the flow nicely and still be pleasant at highway speeds.

 

Why not delete the cat?

 

Why delete the cat?

 

The cat is a flow restriction.

 

Not enough flow restriction to make a difference especially using a contemporary high-flow Cat.

 

It makes enough of a difference to justify not bothering to replace it.

 

It's a social responsibility to replace it, not just a government enforced one. They're on there for a very good reason, and as being someone who's eyes burn from smog whenever there's a local inversion, I'll take every bit of clean air I can get.

A healthy cat has very little detrimental change on performance.

 

He's in Texas. You'll be fine.

 

Seriously, that kind of sarcasm isn't constructive or needed.

It's a mentality that affects everyone everywhere because people want a "little extra" at the expense of everyone else. It's not a mindset that should be propagated on the forums.

 

My truck never had one.

However, I installed an EFI on it, and plan to add the cat as well, and hook up the EGR as well. Just because it ain't there doesn't mean it shouldn't.

Yup, Imma greenie better to build an old truck than throw it away and buy new.

 

Well the truck still has to pass inspection, if it's throwing a code because the converter has been removed it won't pass.

Since I'm replacing the stock 2" headpipes and 2.5" exhaust with 2.25" and 3" pipes AND replacing the 20 year old 2 converter system with a single 3" the exhaust will flow significantly more than it does now. Why not use a part that's gathering dust in my garage to keep it legal?

 

Unless you have both an upstream and a downstream O2 sensor, a malfunctioning or nonexistent catalytic converter will not throw a code.

 

Yes, the truck has two O2 sensors upstream and one downstream from the converter. I'm pretty sure that's why there's no tailpipe test required for OBDII vehicles in Texas.