I have a '89 F150 5.0 AOD. If I delete the cat. conv. will it run like crap?

 

If you keep a muffler on that has some back pressure it should'nt.Just be careful if you have any kind of emmision or safety inspections.At one time the fine was $25,000 to the shop that removes it and $10,000 to the owner if he/she knew it was removed.( of course that's max fines,Federal).

 

WOW! What state are you from with those type of fines?You could always have some gas station that might pass it for the right price !!!!!!!!!!!

 

That's Federal law,they mandate emmision standards before it get's to the state level.

 

you dont need back pressure for it to run right. what you have to worry about with a 4 cycle engine like this is scavenging. you want to have as little of back pressure as possible but you dont want some huge pipe, and if you have short pipes with no muffler or cats you have to worry about frying exhaust valves because the valves cool to rapidly. as long as you have some kind of pipe you should be ok. i cut every thing off but the first cat and it runs just fine, and im soon to gut the first cat and put a glasspack on it and do a side exit right behind the cab and it will be fine

 

No no no!!! its ONLY going to be used for off-road use! :P LOL

 

In a 4 cycle engine a balanced system of intake and exhaust is necessary. If you run an open 3" exhaust system with no cat/muffler and additionally improve the intake performance you will enhance horsepower with the reduction in laminar flow and turbulent flow effect, depending on boundry layer flow as your locomotive driver to regulate and enhance the scavenging effect. If you are going to take the vehicle into an off road situation without sufficient torque to overcome obstacles you are going to generate a large amount of noise while stuck. Torque is a necessary animal in the realm of off-roading, much more so than horsepower, look at some of the rock crawling rigs or the Baja rigs. A full blown header, no cat, high flow muffler system is usless off-road if not balanced by an intake to match the scavenging performance. The Federal fines are very real by the way and also enforced by Rangers, you know the guys in the woods. Spark arrestment is also an issue. I love the outdoors and spend an inordinate amount of time in the North Georgia Mountains on very unimproved roads and paths pursuing the elusive trout.
I spent some time designing austinetic stainless steel bellows for Cat Diesel exhaust systems and our chief engineer brought the tube bender with him that he first built while working for Hooker Headers, guy's name was Terry Rossman. In order to work for him you had to understand at least basic engine dynamics, not just watch it on TV. If a vehicle qualifies due to weight class the exhaust system can be modified. If it is for off-road use only and is trailered, there are exceptions. Then it is not a licensed roadworthy vehicle. As Terry explained for those of us who were novitiate engineers (I only hold an MME from U.S. Naval Postgraduate School in Monterey, CA), he expalined the forcing issue that is much like a swimmer starting freely in the water and accelerating with no encumberance compared to a swimmer pushing off the wall, torque works off the wall, too much restriction and no good either, it's a balance system issue thing. Okay, I'm done.

 

tex you got a point there. i was just trying to say bigger isnt always better in the long run

 

I realize that, you've got a lot of folks who think straight pipes are an answer. They are, just the wrong one for what we do.