I understand the basic premise of the air-pump, but can you disconnect this device without ill effects? I'm understanding it is supposed to have a check-valve, so exhaust shouldn't be able to back-up through it. Point is, could you disconnect this, get rid of it, and get a bigger catalytic convertor? In essense, it seems like I have two cats, one right up front that the pump is attached to, and a standard type, downstream a ways back. Love to get rid of the whole lot!

That depends on what else you remove, and what your local laws have to say about it.
Correct. If your check valve has failed, it can and should be replaced.
No; the lack of secondary air injection would cause a big catcon to overheat and melt down just as surely as it would do the same to a small catcon. What are you trying to accomplish?
The front catalyst is an oxidation catalyst. The rear one, depending on the spec to which your truck was built, is either a reduction catalyst or an oxidation and reduction catalyst. Again depending on your local laws (where are you?), you could reduce exhaust restriction and underhood heat by replacing the two catalysts with a heavy-duty 3-way catalytic converter such as one from Catco's 9000-series. However, you would definitely want to retain the secondary air injection, which is described in greater detail here.

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Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan,
Live in N.J. Just trying to reclaim any power that's possible. Didn't realize the head was involved, so that's what that pipe is for. When you go thru inspections in jersey, you get a print-out and I noticed I was in very good shape considering the parameters they allow you, so I figured I could yank all of this. Nevermind, and thank you!

I will post the section from my 86 Dodge Van Factory Service manual tonight talking about the various check valves and cast converter systems. Mine is on a 86 Dodge van with a 225 built to CA emissions specs. The good news is that the diverter valve on the slant sixes appears to be totally vacuum operated, which means that you can yank the lean burn computer and keep the highly beneficial catalytic converter and air pump systems (I say beneficial since they don't impact performance much and make cleaner exhaust).

You need to leave your emission system intact, then. Air pump, catalytic converter, etc. If not, you will fail inspection. It's not just a matter of what comes out the tailpipe, but also what the inspector finds (and doesn't find) under the hood and under the truck.
Keep the air injection system in proper repair; look at a heavy-duty/low-restriction unitized catalytic converter, and focus on other areas for power improvement. Some '87s had an Oxygen sensor in the exhaust manifold (rear wall of the central collector area). Does yours have one of those?

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Too many people who were born on third base actually believe they've hit a triple.

More likely, the big catcon would run cold and carbon up because of inadequate oxygen to react with the HC and CO in the exhaust stream. the air pump exists to give the catalyst enough oxygen to work with, not to keep it cool. But either way, the net result is a potato in the tailpipe when the cat either melts or clogs. Air pumps draw *very* little power. Leave it alone and keep the associated parts in good working order, and it won't give you any grief.

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Thank you guys, does anybody know where I might find that first, small, (I think it's proper name is a "mini-oxygen convertor") that the air pump and exhaust manifold connects to, has exhaust leaks that are getting into the cab, big "literal" headache!

That's gonna be a toughie...don't think they're available in the aftermarket as a welded assembly any longer. Probably the best route to take is to pick out an appropriately-sized heavy-duty universal "3-way" converter such as a Catco #9005 from a source like www.discountconverter.com . This will go as far forward in the exhaust system as safely possible without getting silly about it, and will have an air injection port that'll get hooked up to your existing air pump system by the shop that installs it. Catalyst efficacy requires exhaust heat, hence the "right upfront" location of the mini-ox catalyst (this was needed to allow the truck to pass the cold-start portions of the Federal emission certification tests). But if it will be difficult to bring the catalyst to the heat, you can bring the heat to the catalyst: Install the new catalyst in the heat-shielded location under the floor, where the second catalyst is now, delete the mini-ox, and wrap the new headpipe with Thermo-Tec. That'll keep the exhaust heat inside the system en route to the catalyst. (The page with installation parts and accessories is Here.

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Too many people who were born on third base actually believe they've hit a triple.

Thanks Dan! My van had the min-ox removed by a previous owner and I have been wanting to replace the second one with a high flow unit. Now I know exactly what to do!

Thanks Dan,
I did find a "pre-cat" that looks exactly like what I have on my '87 Ram-225, at AutoPartsGiant.com, part # 1002 (Pre-Cat 6000 Series if that's any help (Reed?) Might be easier at $166.46, than re-fabbing.

Glad to help. Careful if you go shopping for a "high flow" catalyst; most of them don't catalyse as well as the ones that aren't marketed as "high flow". Remember, even a regular normal "doesn't say high-flow" catcon flows considerably better than the restrictive units of the '70s. Most of the restriction is in the inlet/outlet, which is why we now see conical inlets and outlets. The catalyst loading in the ceramic honeycomb is key to the catalyst's efficacy. The slant-6, owing to its stone-age combustion chamber and other systems left without updating over the years, is a fairly dirty engine, so you'd want to pick a catalyst rated for up to a large engine. The 9000-series, available in a bunch of different inlet/outlet sizes, is rated for up to a 7.5-litre (458 cid) engine.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.