After the cats are put on, I would suggest a full "like" state Emission Test WITHOUT the State feed back computer hook up. It's just as costly to get this type of test as the State Test but it's like paying insurance. But If the truck fails for some reason (emission part is not working correctly), You can get an other used one at the local P&Pull. If you have the offical State Emission Test done First and it Fails, the State may require the failed part to be replaced as a "New" part. The part may not be available new. Then your in trouble with a lot of additional red tape. In California they are doing an additional test to the gas tank: Pressurizing the gas tank for leaks in the evaporation system, overflow pipe, return line and gas inlet. If there are any weak rubber hoses or clamps connected to that test it will show up. You can test it at home by putting about 5 psi of compressor air through the fill hole and blocking the large area with a heavy Duty Automotive type rag. After 30 seconds, remove the rag and if air rushes back to you from the fill spout, you should be ok with that system test.

Well long story short -- I got the catalytic converter installed yesterday and had an hour and a half before emissions closed. My girlfriend was anxious to see if it'd pass so we drove over to the testing facility. Of course, as I suspected, it failed. I called a shop near my house and they were willing to take a look. They have the same equipment as the emissions facility and adjusted the mixture on the carburetor; they said the readings at idle were within spec but at 2500 RPM they were still too high. At the moment they're changing the jets in the carburetor and will get it dialed in and will run it through emissions for me (you have 10 days for a free retest).

On the plus side, I know it didn't fail visually -- technically it should have everything on the emissions sticker under the hood (EGR, air pump, carbon canisters, etc), however they didn't seem to notice or care. They did however take their time checking on the catalytic converter. The last part of the test is the gas cap (not the tank) -- which since it was new, it passed.

Since I really don't have much experience with carburetors, the rarity of the truck, and since I'd like to get the truck legal I think it's worth having a shop fine tune the carburetor. Plus, I'm sure they'll be able to get it dialed in much more accurately than I'd ever hope to here at home. Not cheap, but this is paying for expertise!

High HC at 2500 on this type of truck may mean ignition system malfuntion (complete combustion not occurring). Also bad gas (water in the fuel or just old) will make small misfires at that RPM. ON this type of vacuum emission regulated trucks, it's important to have fresh fuel and a Really Good Warm Engine before emissions test are done (Cold weather can effect the outcome of the test). The Cats work better when they are real warm (A Road test warm up wouild be for freeway speeds @ 65-70MPH for fifteen minutes minimum). It's possible with the altitude your at, the carb was not for mile high emissions (thus jet change). New cats usually will cover over the Hydrocarbon richness. So your carb may have been flooding (just burbling over slightly at the venture fuel vaporation orifice.....like a high float setting).
Your doing the right thing with the other shop adjustments/repairs.

Unfortunately they have the failed report at the shop, but the limits for '81 are 1.2ppm for CO and 220ppm for HC. I'm assuming the plugs are quite sooty since it's been running rich. I did put 17 gallons of 91 octane in the truck just before the test; the rest of the gas in the tank has been in there since September. The engine and everything on it (carb, intake, distributor, etc) is new. All of the parts have about 2000 miles on them.

That being said, I'm sure when the new engine/etc was installed they just slapped the carb on as-is and didn't jet/adjust it (even though the altitude in Wyoming where it came from is very similar to here). It's smelled rich to me since the day I got it running -- as a matter of fact with the original dual exhaust setup it'd even spit out black carbon crap for the first few minutes when warming up.

I feel like having the equipment, time, and expertise to properly setup a carb is a dying art. Modern vehicles with sensors and computers can compensate and keep a vehicle adjusted...but with something static like a carb it's all about the proper equipment and expertise...and I have tons of respect folks that are still willing to work on them!

Lastly (and I don't know if it makes a huge difference) there is a very small electric fuel pump under the bed by the tank. It does run when the ignition is in the run position -- could that be pumping too much fuel to the mechanical pump/carb?

...(Lastly (and I don't know if it makes a huge difference) there is a very small electric fuel pump under the bed by the tank. It does run when the ignition is in the run position -- could that be pumping too much fuel to the mechanical pump/carb?)....

With a new carb, should not be a problem.

Once you get this all resolved the next Emission Test on the Biannual schedule should be a Cake Walk.

Except in Colorado '81 and earlier are annual tests; '82 and newer are biannual ($15 and $25 respectively).

what kind of carb is on there, a thermoquad???
that almost sounds like california standards there....

No, has an Edelbrock carb (and intake/cam). Unfortunately I can't find the model carb in the paperwork (must have been purchased on a different invoice from the rest of the parts)...

Then that's why it failed. The Edy carb is not jetted correctly. It's going to be an expense to get that Edy carb done right. You should look for the original Thermoquad. Sell the Edy.

Here's a nice one (318-360 fits '80-'86 Thermoquad):

http://www.ebay.com/itm/Dodge-MoPar-360 ... es&vxp=mtr

he is going to need the one that is correct for it, not one that is just close....
depending if the truck has a camshaft, it could have a little too much overlap on the valves too.....