Engine restricting emission removal

[olymunch]

Does anyone know what emission stuff can be removed in order to improve HP and fuel economy?
I've heard of people blocking off the egr and removing the cat on their non Amc cars and getting better performance.
I'm installing a crate 258 and upgrading to the 4.0 and mpi so if I can also get rid of all the crud that restricts my engine that would be great. I'm smog exempt.
Thanks

[rohnk]

I'm planning for this on my 4.2L in the near future. If you have an air pump, that can go along with the air injection manifold and the hoses and vaccum diverter valves. It also has a hose that goes into the cat converter and you can either remove the cat altogether or just plug the air line going to it.

The EGR and CTO can go along with a half a mile of vac lines. Then you can remove the A/C compressor and move the alternator up if you want too. I don't really care to have A/C so I will remove mine at some point at least on the engine side of things. I may just block off the lines going to the condenser since it is under the dash and a lot of work to remove.

[olymunch]

Thanks that's what I'm looking for!
Anyone have any success with these kinds of mods?

[carnuck]

Just keep in mind that removal of your cat here in WA can result in a $5,000 fine from the EPA if you're caught. Mine is going to a high flow cat (for what I can get for my old one for scrap, I can afford a new one)

[ammachine390]

When all the emission controls are functioning properly, removing it will not really help your horsepower or fuel efficiency. The only one that actually uses engine power is the air pump (if you have one), and that load is quite negligible.

That said, most of them can be removed.

[olymunch]

Ammachine390, yea but that's a big IF. I'd rather just take off all those vacuum lines. I love my eagle but man does the engine compartment look cluttered. So if I can un-clutter it and raise the performance and eliminate the headache of emission control things then I'm all in.
Carnuck, I'm pretty sure 30 year old cars in WA state are exempt from smog regulations, plus how would anyone ever find out. But still 5k? Thanks for the heads up

[mudkicker715]

Technically its a federal thing with fines to remove a cat.

mine are currently being replaced due to theft iirc. might have forgot who took them and might have forgot when. couldn't remember but thought i replaced it. sorry will get right on that.

[rohnk]

Don't forget about the savings in weight. With all the extra "stuff" you will probably save 40-50lbs of weight up front.

[vangremlin]

I don't think that removing the emissions control equipment will result in a big horsepower improvement.  I think it might run better (less stalling, hesitation, etc) but I doubt you'll see a real difference in acceleration or top end speed.

[olymunch]

Maybe, but any gain would be worth it. Especially just aestheticly, I really like a clean engine compartment but almost every one I've ever seen looks like a rats nest, even very well taken care of ones.

Does anyone have any experience with this kind of job?

[rohnk]

I will soon! Maybe we should compare notes. I plan to start on it this weekend.

[vangremlin]

I still have my catalytic converter, and my EGR, CTO, and smog pump are still in place.  However, I removed the belt from the smog pump, and I don't have the vacuum lines hooked to the EGR or the CTO, and I removed the stuff that was on the top of the valve cover.  I also switched to the Gronk's Motorcraft carb, and my car runs great now.  As I said, not much improvement on performance, but it runs better.

[BenM]

I would also think that removing most items won't make a difference, except for an air pump or an old pellet-type catalytic converter. Monolithic converters on a stock engine just wouldn't be enough of a restriction.

While articles on cars seem to all state that emissions devices robbed power, the numbers for the 258 are pretty consistent and the last 258s got higher compression and slightly better (though still poor) cams. In '72, right in the middle of adding emissions devices ratings went from gross to net so the same engine with no changes whatsoever from 71 to 72 lost 1/4 to 1/3 of it's "horsepower". According to a Chilton's I have handy in '75 the 258 made 110 hp and in '87 it made 112.

That said, if you're putting the Mopar MPI system on it (as opposed to the Renix) there's very little emissions equipment as a part of it. Only the cat is notable, and at least some versions throw a code if it's not working so you might need it to pass inspection depending on your local regulations.

[rohnk]

I think the biggest gain is not intended to be HP but less stuff to break. I don't expect more power at all. I just want to minimize the stuff in the way.

[olymunch]

Ya that's %90 of it for me as well, my egr went bad in my truck and it took me a while to figure it out because it was staying open creating a vacuum leak. After much diagnostics, it only happened at high speeds under load, I found it and replaced it. The only reason I didn't block it was because the block kit was about the same price and not available that day and I was just tired of dealing with it. And of course a cleaner looking engine bay.

So I've got the 81 sx4 that was switched from an automatic to a 5speed. Is there any way to tell if I have the air pump or a diagram showing where everything that I can take off is?
Rohnk, when you do yours can you take pics if its not to much trouble? It would be a great write up!