Background history:

last year my brother asked me to give his 1983 Dodge van with a 225 a tuneup because it wouldn't pass emissions. The van had NO emissions equipment (previous owner had ripped them all off) so I ordered an aftermarket catalytic converter and cobbled to gether an AIR injection system from junkyard parts. The van passed emissions great so it went back to my brother.

At that time, the van got about 18 MPG on the highway and had good power.

Flash forward to this week. My brother dropped the van off again, complaining about poor gas mileage. he wanted me to tune it up for him again. He said tht the van was now getting about 10 MPG.

Well, Joshie225 gets a gold star. In another thread he suggested that the poor performance and gas mileage of the van was due to a failed catalytic converter plugging the exhaust. DING! He's right!

I cut the catalytic off today and discovered that the honeycomb had completely fallen apart and large chunks were clogging the muffler and the catalytic body itself.





What worries me is that the honeycomb has actually melted. I think this is because the system I cobbled together constantly injects air into the catalytic when the van is runnig. I am afraid that this is overheating the catalytic and caused it to melt. However, I am not an expert in these things and don't know if my theory is true or not.

Now I am left with the question of whether or not to install a new catalytic and muffler or just install a new muffler and take off the home-brewed air injection system. The van is over 25 years old so it is now emissions exempt in Washington State.

Help!

About 4 years ago the same thing happened on the OEM converter on our 93 Dakota (bought new). New converter & muffler and good as new with no further problems

Converters almost never die of natural causes. They are almost always murdered. The meltdown you experienced is due to excessive fuel reaching the catalyst, driving its temperature way, way up. If you replace the catcon and do nothing else, the new cat will fail again in the same way.

The constant air injection isn't the problem; that's how factory air injection systems work (with the added function in many cases of injecting air into the head rather than into the catcon when the engine's first started, to bring up the exhaust temperature quickly so as to get the catcon up to operating temperature in a hurry). It is very difficult to prevent excessive fuel reaching the catcon without a closed-loop fuel system of some kind — an oxygen sensor talking to a computer which controls the mixture via a feedback carburetor or, much preferably, a fuel injection system. Catalysts were used with open-loop carburetors from 1975 to 1980, and in some cases later than that, so it can be done...but the carburetor must in that case be tuned to run leaner than would be desired for best driveability and mileage through its whole operational range. This is a major reason why the cars of that era have a reputation for poor driveability and mileage and finicky tuning needs. It goes (almost) without saying that ignition must be absolutely perfect.

How to proceed from here depends on what this van's fuel system configuration looked like from the factory, and what it looks like now.

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

The lazy method is to hollow out the existing cat and use that.

Then, just before a smog test put in a good cat, pass smog, take out good cat.....................

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

He said it's exempt from smog tests so I would simply remove it.

PS. File this in the "No good deed goes unpunished" category.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Ah, I overlooked that part about emissions exemption. In that case, yes, I think Dakight's right. Carburetors + catalytic converters were a poor marriage in the best of circumstances. Make your environmental contribution by maximising the vehicle's fuel economy.

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

Ahhhh.

Well, here's the emissions history of the vehicle, as near as I can tell:

Dodge built it in 83. It was a single barrel lean-burn equipped vehicle with the Federal emissions package (dual cats and air injection)

Someone bought it new, then probably someone else bought it, then a Russian contractor living in Tacoma bought it. One of those guys, my guess is the contractor, pulled all the emissions systems and did a bad job patching the motor back together (the contractor complained it lacked power). Then my brother bought it.

I swapped the (worn out) 83 hydraulic motor out with a 76 Volare motor that had been rebuilt to stock specs. Left it a single barrel carb with no emissions or cat (Holley 1945).

Then I swapped it to a Super Six and tried to piece a catalytic converter and AIR injection system together. It then passed emissions and my brother was happy. Then it started getting bad gas mileage and it came back to my house.

If the melting is caused by excessive fuel, then methinks the Carter BBD on it is toast. Good thing I have a replaement Holley 2280 coming.

I will just replace the muffler with the Walker muffler Dan recommended a few months ago (its the same one you have on your truck Dan) and remove all the catalytic and AIR injection stuff.

It makes me happy I was at least able to reverse engineer a functional system from reading the shop manual though. If nothing else it was a learning experience!

Thanks for the info guys!

FPC suggests no feedback/no O2 sensor in '83 except in California.
I remain happy with mine.

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

It might have been a California emissions package then beacuse it was definitely a feedback carb and the original exhaust manifold had the port for the O2 sensor but someone had remove the sensor and run a bolt (with the wrong thread I might add ) into the hole to "plug" it.

Glad to hear about the muffler. I am hoping to get it welded in tomorrow so I can hear it.