Truck Failed Inspection
 

I have a 1979 F-250 with a 351M 2 barrel that failed the CO part of the Delaware emissions. Does anyone know of any tricks to help me get this through? Do I have to lean out the carb a bit?

Thanks!

Carbon Monoxide or CO is formed by combustion in an over rich mixture. The idle screws will only lean the mixture at idle. If your engine failed at part throttle, it cannot be fixed with the idle screws. It may be due to some problem in your carb or intake. Do you have a clean air filter?
Is your carb float setting or your fuel pressure right?
What color are the plugs? Do they show a rich mixture?
How is your Hydrocarbon reading? Rich mixtures should also produce high Hydrocarbons.

I agree, You might wanna pick up a rebuild kit and give the carb a good cleaning.

The emission inspection was done at idle. The hydrocarbon portion of the test passed very well. The air filter was recently replaced and I have not check the plugs as of yet. Maybe some carb cleaner and lean out the carb a bit????

Thanks!

Was there anything they tried to get you within limits? They should have tried some minor adjustments eg. adjust carb/timing before failing you. Do a search on this site for sea foam, the stuff works awesome.

Reduce the idle RPM as low as possible, get it smooth, then lean it a litte more.

Thanks danlee! Do I lower the idle using the mixture screw?

No, there is a seperate idle speed adjustment. It sould be where the linkage connects to the throttle arm.

bump up your timing...

get your temp up also as this will help keep it lean, just don't go to hot.

higher heat range plug will help too

Thanks for all the information guys! I have been busy and have not had time to work on the truck. Hopefully, this week I will try some things and if I have time I will run it through. I will report my findings.

Thanks!