Rebuilt heads still failed emissions any pointers?

[Jeremy0201]

So I'm at my wits end.. So I gambled rebuilt heads didn't touch the bottom end after machine shop said everything was loose on the heads. Took it through emissions and still failed horribly.. I strobe timed it and I'm not a carb tuner but two barrel motorcraft bottom screws three turns out, the rest of it set to run ok... So is it oil slipping passed rings or might I just need a proper tune up?????? 302

 

[broncnaz]

A lot depends on what part you failed. Different failures mean different things. Normally you want to set the timing to the stock setting or maybe even a little below it. 3 turns out on the mixture screws is not really a setting you need to turn them to get the highest smoothest idle. Usually the basel ine setting is about 2 turns out which gets you in the ball park and adjust from there.
Might want to post what parts of the test you failed and post more about your engine and actual timing you have it set to.

 

[HillbillyDeluxe]

Post up your emissions readings and lets see what you have. I used to live in Tucson so I know how to read the results.

Btw, a trick you can use to pass emissions is to run over to Don's Hot Rod Shop or Townsends and get 3 or 4 gallons of methanol. Before you get to the emissions place stop a few miles away and put the methanol into your tank. I liked to mix it with about the same amount of gas. Since methanol burns clean, it will reduce your emissions output, hopefully to a level that will pass.

 

[rastiss]

Since it takes twice as much methanol to run as gas, it makes for a leaner mixture and leaner should be cleaner. So yeah, I'd think that would help.

 

[broncnaz]

Only if you failed due to running rich. Running to lean can cause failures as well.

 

[HillbillyDeluxe]

Only if you failed due to running rich. Running to lean can cause failures as well.

Well yea, I guess I should've been more clear on that. But thats why I asked him to post up the results. Might as well figure out why its failing.

 

[Jeremy0201]

1st idle hydrocarbon 4068 Carbon monoxide 10.70

Pre condition reading hydrocarbon 417 norm 380
Carbon monoxide 7.26 norm 3.0

Final reading. Hydro carbon 2134 norm 450
Carbon monoxide 11.36 norm 5.0

 

[Jeremy0201]

Fudge at the bottom it states my previous levels. HC 2318
CO 9.43
They got worse????

 

[HillbillyDeluxe]

Since it takes twice as much methanol to run as gas, it makes for a leaner mixture and leaner should be cleaner. So yeah, I'd think that would help.

It worked for my trucks as a teenager. My '78 GMC 4x4 had an 11:1 383 that wouldnt pass so I used the methanol trick (something ike 5 gallons to 4 gallons of gas) and it passed no problem. My '85 K5 Blazer had a shitty 305 with a quadrajunk that no matter what we did it would not pass. My dad even took it to as shop to have it tuned up and it still wouldnt pass. I put 5 gallons of methanol in it and ran it through like an hour after it failed the 2nd time and ended up with the same inspector. It passed with flying colors and the guy was just at how much cleaner it was running. He asked me what I did and said something like "I figured how how to tune the carb ;D". He was baffled how it failed so bad and an hour later it was cleaner than most new cars.

 

[HillbillyDeluxe]

1st idle hydrocarbon 4068 Carbon monoxide 10.70

Pre condition reading hydrocarbon 417 norm 380
Carbon monoxide 7.26 norm 3.0

Final reading. Hydro carbon 2134 norm 450
Carbon monoxide 11.36 norm 5.0

Fudge at the bottom it states my previous levels. HC 2318
CO 9.43
They got worse????

I had a feeling it was gonna be bad lol. Seems to be running rich. How does it run?

Now I remember why I registered all my vehicles in Sahuarita so I didnt have to mess with emissions anymore.

 

[broncnaz]

Most likely backing the timing down to where it runs kinda crappy will do the trick. Once you pass you can turn it back up to get your power back. Dont know what all you've done to prepare for the test but make sure the plugs, wires, cap and rotor are all good Might pay to put n a new air cleaner as well and make sure the choke is working properly. Also make sure the engine is at full operating temp before testing.

burning oil will result in high HC levels but yours are not that high. So even with worn rings I dont think you would fail if the engine is tuned properly.

 

[Jeremy0201]

Yea it's bad .. Maybe needs a new carb the bottom screws turned all the way in don't seem to slow idle speed my thoughts would be it should kill by then.. Definitely rich..

 

[broncnaz]

Get you a rebuild kit for the carb. clean it out real good. Set everything to spec. Then see if you get any adjustability back. turning the idle screws in should have some effect and will usually kill the motor.

 

[Jeremy0201]

Thanks great ideas, I won't break into the engine again just yet

 

[jim3326]

If you have an extra vacume line you could always pull that and lean it out. Of course it would have to be hidden:-X

Jim W.

 

[WheelHorse]

What year is your rig?

Is it suppose to have a cat on it?

Oil burning has nothing to do with sky high CO and HC's...these are rich mixture indicators and you appear to be washing down your cylinders...

I'd recommend a carb rebuild and the floats set to the appropriate level.

Hook up a vacuum gauge. Slowly turn each idle adj screw in until she starts to stumble...this will lean it out and then turn each screw out slowly until you achieve the highest vacuum possible. Add a smidge 1/8-1/4 turn out beyond the highest vacuum.

Make sure P&C are new if you still run that set up. Ensure all wires and plugs are new. Cap and rotor.

Ensure oil is changed after you rebuild the carb and tune it properly. Oil that has been contaminated by rich mixtures will still cause the rig to fail even after everything else has been corrected.

Leave timing at base.

Any carb'd vehicle that I had tuned back to '68, when we had to pass an idle test, was never over 250 HC's with most around 180PPM. This was with no cats and no air injection.

 

[WheelHorse]

If you have an extra vacume line you could always pull that and lean it out. Of course it would have to be hidden:-X

Jim W.

That and leave the air cleaner out of it LOL.

 

[broncnaz]

Burning oil has everything to do with HC and Co output. As thats what not fully burned oil produces. Guess where gas comes from? also if your burning oil less gas will burn as well causing the overly rich condition. But I dont think he's burning enough to cause the higher readings. As his numbers are just not that high.

 

[broncobilly72]

Related story...had a toyota truck years ago..would not pass smog...went to a a special smog station and was told repairs were too expensive so the state let me slide for that year. Never did anything to the truck except add some carb cleaner and 2 years latter it passed smog! We named the truck Christine! I think the carb rebuild idea is the best. I usually set the adjustment scews 1 1/2 turns out hook a vacume guage and turn the screws out till i get the best idle.

 

[Broncobowsher]

As stated before, running really rich. I bet you can smell the truck it stinks so bad. At 10% CO you are so rich that you can't even partially burn a big chunk of the fuel and that leaves raw fuel (the HC is hydrocarbon which is oil and fuel) to come out of the tailpipe.

As it leans out the HC will come down, then the CO will come down. Lean it too far and the HC will start to go up again (due to a lean misfire). Turn the idle mixture screws in to lean it down.

The closer to zero you set the timing the cleaner (and more gutless) it typically runs.

You should have 2 sets of numbers. One for idle the other for cruise. the idle mixture screws work for the idle test and some of the cruise. If idle comes out clean and cruise is still messy that is other things in the carb that are wrong.

It really is best to tune on a 3 or 4 gas analyser, it can be hard to do by feel even by those who have done it for a long time.