67 F-100, 352, dual exhaust, headers, 2bbl carb, manual choke, electronic ignition, good plugs & wires, good PVC valve, timed at 12° btdc.

Well, I was hoping that good behavior (2 beers at last night's party in Yuma) would result in good luck at the Arizona emissions test but... What's the best way to get my truck to pass? It is reading high on both hydrocarbons (573 vs. standard of 450ppm) and carbon monoxide (9.1 vs. standard of 5ppm). My trucks runs like a dream; I just can't pass the damn test! Thanks for your help.
jor

 

Make sure the engine is good and warmed up.
And a good basic tuneup never hurts -- plugs, wires, points, all adjusted to stock.

If you've already taken those precautions you can read on...
Normally bumping up the idle speed helps. Retarding the timing a little will raise the exhaust gas temperatures and give you more port oxidation to burn up those HC emissions. You're pretty close to passing, so a small change may help.

If you can chose between regular, ethanol, and MTBE gas, pick the ethanol or MTBE. They contain oxygenates which naturally lean out the mixture. Those should knock down the CO emissions.

I don't want to make too much of a corporate plug, but I've heard from good authority that a 20 oz bottle Techron Concentrate in your gas each oil change will keep deposits off of your intake valves and carburetor parts, and give you the best chance of passing.

One of the rare loopholes for us in CA is that pre '73 vehicles don't need inspections.

Good luck!

--Matt

 

I too have to deal with Az emissions (Phoenix). I am going to assume you have done all the normal tune up stuff,if not get them out of the way.

Do a compression test, you need to know what your dealing with. Write down the figures.

Next get a hose adapter that goes into the spark plug hole. One by one roll the pistons to the top of the cylinder on their compression stroke (follow the firing order).Plug your shop air into the adapter and listen for where the air goes. Make sure the piston stays on top.

If you hear air coming out the carb, you have something holding the intake valve off the seat. Not likely, but possible.

Listen to the oil filler opening. Air going past the rings can be heard here. Listen carefully for differences between cylinders. Any engine can break a ring and loose a small amount of compression but it probably wont show up in an emissions test unless the compression is under 95lbs.

Exhaust pipe will be the next and most likely place to listen for escaping air. Get an ear plug for one ear and a piece hose about two feet long for the other ear. I use a thin wall clear 3/8 OD. Get on the floor with 1 foot of hose up the tail pipe. The surounding location should be quiet.

Any air noise or hiss coming from the tailpipe is a real problem. The problem is it will not get any better by itself. But you can help delay the inevitable, but it's quite a task. Wont get into that yet.

All this rotating and listening should take about an hour and a half. If you rush it, your not doing a thorough job.

Hydrocarbons out the tailpipe are most likely attributed to air fuel mixture sneeking past the exhaust seat during the compression stroke before the cylinder fires. If you have a large cam or carb you may need to make other adjustmenst.

Do you have a vacuum guage? Get a reading at idle, should be 17-19 inches minimum.

Keep us posted and good luck.
"HEFTY"

 

I had a later model car that wouldn't pass, bougt the bottle snake oil that gauranteed to make it pass, NO GOOD. I took it to a private shop and the owner lowered the idle and bingo passed with flying colors.

Are you sure a 67 has to pass emmissions, That one should be exempt.
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John

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In the cool still quiet of night, you can hear chevies rusting away.

 

Thanks to all. I'll give these suggestions a try. Re the 67' having to go through emission testing, unfortunately, Arizona requires 1967 and later. I'm not sure about the other states.

 

Emissions on a '67, that sucks.

jor, it sounds real rich, try thus. Back off your initial timing to 6* BTDC. Adjust your mixture screws starting on the lean side and richen it to the point that the idle speed stops increasing. Now lean down the mixture screws until the idle speed drops around 50 rpm. Finally set your idle speed. I'm assuming you don't have a cam.

A fresh oil change can't hurt either.

Barry