Exhaust manifold versus headers and cat delete?

[longhunter]

Hello all,
I have heard several sides of the question is iy better to replace the manifold with headers. I have heard yes and no. Just your thoughts on it would be appreciated. Do you gain any perfprmance? And I was told that with long tube headers it would cover things I could no longer have access to and could overheat things, maybe oil pan or transmission pan?

Understanding the legality issue and environmental issue, is there any performance to be gained from removing the cat?

Thank you!

 

[Tiha]

It depends on the year you are working on.

The Speed density systems gain very little with headers. But there is a gain.

Mass air flow systems stand the best chance of gaining from headers and cat removal.

Long headers or short. You probably won't notice a difference. I like the short headers myself because I do like access to things like the starter and like you said the extra heat. But really long tube headers will not do that much damage to any of those items.

There is always advantages to a free flowing system. It should be more efficient. Better mpg but the gains may not be notices unless long high way trips.

Just my opinions.

 

[longhunter]

It depends on the year you are working on.

The Speed density systems gain very little with headers. But there is a gain.

Mass air flow systems stand the best chance of gaining from headers and cat removal.

Long headers or short. You probably won't notice a difference. I like the short headers myself because I do like access to things like the starter and like you said the extra heat. But really long tube headers will not do that much damage to any of those items.

There is always advantages to a free flowing system. It should be more efficient. Better mpg but the gains may not be notices unless long high way trips.

Just my opinions.

Thank you. I have a 1996 and am going to change the exhaust anyway so I can ride with the rear window down without it sucking in exhaust from the rear exhaust exit pipe. Thinking about making it a dual exhaust system exiting in front of the rear wheels. Always thought catless would be more efficient and perhaps better fuel economy but just my thoughts.
If I did go catless what lights would come on on my dash? Check engine or something else? Would I need any "reprogramming" of the ECM or something else to make it run without cat?

Thank you.

 

[Tiha]

You still need the first oxygen sensor to keep the engine running correctly.

You can install the second oxygen sensor, even though there is no Cat. If you use a spark plug anti fouler the engine light will not come on. You can find them in most auto parts stores in the help section.
Been a while but I am thinking you have to drill it out some to clear the sensor.

If you don't install the 2nd oxygen sensor then you will need ECM programming to keep the light off. I have no idea who does that stuff anymore.

 

[longhunter]

You still need the first oxygen sensor to keep the engine running correctly.

You can install the second oxygen sensor, even though there is no Cat. If you use a spark plug anti fouler the engine light will not come on. You can find them in most auto parts stores in the help section.
Been a while but I am thinking you have to drill it out some to clear the sensor.

If you don't install the 2nd oxygen sensor then you will need ECM programming to keep the light off. I have no idea who does that stuff anymore.



View attachment 32808

You still need the first oxygen sensor to keep the engine running correctly.

You can install the second oxygen sensor, even though there is no Cat. If you use a spark plug anti fouler the engine light will not come on. You can find them in most auto parts stores in the help section.
Been a while but I am thinking you have to drill it out some to clear the sensor.

If you don't install the 2nd oxygen sensor then you will need ECM programming to keep the light off. I have no idea who does that stuff anymore.



View attachment 32808

Tiha, thanks you for the info. I will try and find the spark plug anti-fouler at a store just in case I decide to go that route.
Really was hoping for a measurable increase in horsepower.

Thank you, again.

 

[96XLT]

I have Bassani short headers & y-pipe with cat. I bought my 1996 with the rear cat cut off and 3 inch exhaust pipe. I had a 84 XLT 5.0 that I gutted the cat before replacing it. The only thing I noticed with no cat was a much heavier gas smell, a chance to backfire, and creating a louder blub-blub noise when decelerating in 1st gear. I had no changes in MPG for either vehicle without the cat. When I installed the Bassani headers and y-pipe with cat, I did notice better performance but I also went back stock diameter on the exhaust pipe. I had no other changes to the engines on either Bronco. When you modify the engine to require more exhaust flow than stock can provide is when you see performance gains.

The one reason removing the cat will help is if the existing cats are clogged.

Also good to note, I have had to tighten the headers on occasion and have required gasket changes. Never had the issue with manifold as long as they do not crack - which is why I went with headers when replacing the y-pipe/cat.