I would like to find out if I can clean up my Stock exhaust manifolds. 4.6L 2000 F150 I just want to clean my stock manifolds to get some better performance. I really don't want to buy headers. Any help with this would be appreciated.

 

Not saying it wont help or cant be done, just I really don't think that doing much of anything to the stock exhaust manifold (EM) is going to produce any measurable improvement.

Yes you could port and polish those stock EM and help a bit, but the amount of effort and or dollars spent will not yield enough to justify it, outside of knowing what you did. everybody will generally go and then. teasing of course.

Now you might find some stock EM from a different application that are a bit longer, or different style then yours, like maybe from a mustang, crown vic, or expedition or something that have better flow characteristics. Then you will have to be aware if those are the same head configuration (meaning; 2v or 3v or 4v and bolt pattern ), and getting the EM to clear everything (meaning; frame rail, starter, tranny, etc) and then match up the rest of the exhaust in your f150. It would take some considerable research.

In short, if you need to do all that anyway... then headers are the way to go. long tube with a custom tune to account for the new exhale, would yield the most performace gains.

If you want to just make it look better, then new stock EM and some high temp paint. There again , that is a lot of effort. If the originals are not leaking then just clean them up and a few passes with the high temp paint , will be the low buck winner.

 

My opinion on that issue: If the Factory Engineers thought a Polished Exhaust manifold would help, it'd come that way from the Factory.

Long ago and far away, I worked for a long time on some Ford 292 or 312 Exhaust manifolds that had a little casting Slobber near the intake hole.
I got so interested in doing that, I bought special tools, had some welding done....I could have bought a bigger engine for all I had in that.
I never could see a difference in the engines after that Polishing job.

A friend put Headers in his old 56 Ford. The Heat burned up something in his car.

Better leave it stock so you wont have to fiddle with it when you get all done improving it.