I have a 2000 150 , 5.4l v8 . do I need both cats or will one work. the small angled one is rusted thru and and the second one is plugged . can I replace both with one aftermarket cat ???

 

I find that a little hard to believe if they are stock. The T409 steel that Ford uses takes 12-20 years to rust through even in high road salt areas. Many aftermarket converters might fail faster than that.

A more likely situation is your is leaking because the converter has been overheated repeatedly because of tuning problems. This causes the metal to harden and crack.

Can you replace both with one aftermarket cat? Yes and no. From a strictly legal standpoint, no, but depends on your local emissions enforcement. From a functional standpoint, yes you can. Its probably worth the effort to see how strict your local emission laws are. If they are very "by the book", then you will need to use 2 cats per side, but if they are not picky at all, then just one per side will work just fine.

Just be aware not all aftermarket cats are equal, in fact far from it, there are enormous gaps in quality, even among different brands in the same price range. Especially if you are asking one cat to do the work of 2, you need a cat that will handle that.

I recommend the ones from Bear River Converters - Wholesale distributors of catalytic converters. Those are good cats that are reasonably priced. They have higher loadings than the other stuff out there, longer warranties, better construction in general, and they are made in the US. Stay away from generic cats, Magnaflow and Catco those brands have inferior quality control and low precious metal contents. Their cats are a gamble at best. If you get lucky, they can be pretty good, but even if they work, you are paying way too much for what you are getting.

This is the unit I would use.
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