I have 1985 Class C Ford E350 with a 460 carberated engine. I just had the carb rebuilt and it is now running like a top. Carb is a Holley 4180 I believe. Problem is it failed its smog test today. I have turned a few wrenches and even rebuilt a motor or two but I am not good at diagnosing these types of problems. I have searched the web and forums for ideas and now I am turning to my fellow RVers. It did not pass the HC Test. The HC readings were 950 first idle and 1000 second test idle after reving the engine. Passing is 350. Where should I start? Should I lean out the air/ fuel idle mixture? If so how much? 1/2 turn ? 1/4 turn? I will check the timing but I am not sure about the dura spark distributior on it. Do I check it like a regular distributoir for time? Can it be the EGR valve? I just hate to throw parts at something without knowing whats wrong. Thanks for any help that you may have.

Not a lot of people here with a FORD 460 motor in a motorhome. Seems like everybody I know with a 460 motor in something has problems with the carb. The original can't be replace, so something else has to used. You might have to go to a smog repair shop to have it tuned or de-tuned for smog. If you start changing the vacuum valves or jets, you could easily get too lean causing more problems. New standards for older motors do not help your motor at all. Good luck.

I have a solution. Move out of Oregon..:B

Its definitely carb tuning. If its tuned right it will pass no problem. My old boss always used a cylinder balance analyzer for tuning. You can also use a wide-band O2 sensor. You could just try small changes on your own (lean it out), and just keep going back to DEQ for a free air-check (you don't have to do ay paperwork if you ask for the free air-check) until it passes.The good thing about this all is you will stop wasting extra fuel once you get it tuned right. I just realized yesterday how big of a jump fuel prices made again:E

Easiest is to find someone who knows how to adjust it and has a sniffer he can use to adjust it to. Back in the old days i used to have to adjust lots of cars so they ran like******just to pass deq. Then readjust them to run right.

I hate to pay a mechanic $80/ hour to just make a small air/ fuel adjustment so I guess the guys at the DEQ will get sick of seeing me. The funny thing is that it passed 2 years ago before I had the carb rebuilt. Guess I should have left well enough alone. I would like to have it dialed in to shave off some of the fuel bill too.

Failed Smog Test | Good Sam Community

bosco0104
Explorer
May 26, 2013
Well I took it in yesterday for another test. FAILED !!!! Not as bad as the first but still failed. Before I took it in I checked for any vaccume leaks with propane. None found. I adjusted the curb idle because it was way too high. Test showed around 500 +/- HC. Half of what the first test was at 1000. Getting closer. Guy at the test station said a lean misfire again. I tried to adjust the mixture on the carb but I am having trouble accessing the screws. i am not sure if they are still filled or I cant get the right angle on them. Is there a special tool for Holley or just a flat blade? i would think since I just had it rebuiklt that the lead plugs would have been removed. I need to get my mirror down ther to be sure. So with that said i have now replaced cap, rotor, wires yeaterday and did plugs last year. 1 more test and then its going to the pros. More to come.
Dakzuki
Explorer
May 24, 2013
bosco0104 wrote:
Well put !!! I am going to try to check for leaks. If anything is found then i will fix. If not I will tune the mixture a bit, take it for the air check. If it does not pass then it goes to the pros. Oregon air law gives a cut off year not the age. I believe the year was 1975 for Oregon.

Rubber vacuum hoses are a common culprit. Hose is cheap so it's often better to be on the safe side and replace anything questionable.
bosco0104
Explorer
May 24, 2013
Well put !!! I am going to try to check for leaks. If anything is found then i will fix. If not I will tune the mixture a bit, take it for the air check. If it does not pass then it goes to the pros. Oregon air law gives a cut off year not the age. I believe the year was 1975 for Oregon.
Jim_Shoe
Explorer
May 24, 2013
Pay the mechanic the $80.
I remember the story about the guy that got a $100 bill for some repair. He asked for an itemized bill.
Turning screw - $.50
Knowing which screw to turn, which way, and how much to turn it - $99.50
Dakzuki
Explorer
May 24, 2013
carringb wrote:
Dakzuki wrote:
If the HC is too high you are too lean. High CO is too rich. You may have an intake leak causing the lean condition. Check for bad vacuum hoses and anything that was disconnected. I presume the vehicle wasn't hooked up to a sniffer after the carb was put back. It should have been to at least validate the idle mixture.

High HydroCarbons is unburned fuel meaning too rich. CO means incomplete combustion, which could be form many reasons. Too lean shoots the NOx up.

I used to do this for a living back in the day before OBD and much in the way of EFI. You can put a car on a sniffer and watch the results as you tweak the mixture. Lean out the idle, and HC goes up as CO goes down. Unscrew the jet and watch the opposite. Intake leaks will lean the mixture and raise HC.
aruba5er
Explorer
May 24, 2013
Don"t know a thing about Oregon but in WI you don"t need to pass a smog test after 20 years. And most states use OBD only and yours did not have one. My 1985 F350 460 burnt off the air injector tubes on the right side and we ended up removeing ALL of the emission junk. both pumps, air injection, more vacummn hoses , egr. everything. Ford never knew they could build an engine that ran so fine. Like a watch. And the MPG went WAY up Check and see if a vehicle that old needs a smog test.
j-d
Explorer II
May 24, 2013
You sound like you know what you're doing but I'd be remiss not to say:

BE CAREFUL!

A friend was badly burned working on one of these E-Series. Yes, he'd messed with the wiring, that kept the fuel pump running, and flooded the engine with gasoline. When it backfired, it set the dash on fire along with his clothing.

You're living IN it while you're working ON it.
bosco0104
Explorer
May 23, 2013
I think I am going to put the propane to it to check for any vaccume leaks then go for the mixture. Saturday will prove or disprove a larger problem. I will post my results after that. Thanks
j-d
Explorer II
May 23, 2013
That carb has four-point idle. Adjustments on the rear barrels as well as the front.
JaxDad
Explorer III
May 23, 2013
Mine flunked the first test after I bought it also. My first thought was to start eliminating potential 'simple stuff' then work up from there. (Mines a fuel injected 460 though.)

I got 4 cans of Seafoam, when I put the first 1 in through the brake booster vacuum line the cloud of******coming out the tailpipe was so big a neighbour called the Fire Dept! I then put 2 in the gas tank, and took it for a 2 hour drive. Then put the last can in the crankcase and drove to town to get an oil change and re-test.

The re-test showed dramatically lower numbers, almost but not quite a pass.

New plugs, wires, and dist. cap was enough to get me below the limit.

Forum Discussion

Failed Smog Test

About Motorhome Group

Related Content

California smog RV surcharge

TC Fails Pic Dump

Failed Inspection

Keystone Fail-Sky River RV Fail

Toy hauler fails