Emmisions help

[SleeperT-Bird87]

Took my car today failed misrably

HC 1570ppm state limit of 220 ppm

CO 2.50% state limit of 1.20

CO2 8.28%


motor is a 310 cu in SBC less then 500 miles, [email protected]/.500 lift cam, holley double pumper,3" exhaust timing at 30* locked

AFR at idle is 15.2-16.0 1,200 rpm idle

[Silver68RT]

Re: Emmisions help

Do you have a catalytic converter on it?

[shaun callaway]

Re: Emmisions help

the afr should be a little richer stoich is 14.7-1, shouldnt the idle be around 800-850. is the cam stock or is it bigger than stock. why is the timing locked at 30°?

[SleeperT-Bird87]

Re: Emmisions help

the afr should be a little richer stoich is 14.7-1, shouldnt the idle be around 800-850. is the cam stock or is it bigger than stock. why is the timing locked at 30°?

http://www.cranecams.com/?show=browseParts&lvl=2&prt=5&Vehicle_Type=Auto&Cylinders=8&Engine_Make=CHEVROLET&Year=1969&Engine_Size=262-400%20C.I.&partNumber=10011&partType=camshaft

Thats the cam in it. timing is locked cause i spray it a bit.

[shaun callaway]

Re: Emmisions help

why dont you unlock the timing and see how it does?

[SleeperT-Bird87]

Re: Emmisions help

why dont you unlock the timing and see how it does?

I may try that I have a spare distributor I could swap in.

[TheSilverBuick]

Re: Emmisions help

What kind of test was it? The two speed dyno? I'm not conviced the timing is going to help your HC's and CO's. The CO's will drop with HC's, if you get the HC's below the limit and the CO's are still above you will need an Air/smog pump.

Were the NOx measured? That is what is usually efffected by timing and real-lean conditions. Not that it was asked, but mitigators for NOx are the EGR, Catalytic converters and Timing.

The HC's being high is just being plain rich on the cruise circuit, sounds like a de-jet is in order and hope the over lap in the cam isn't bad enough to make you still fail from raw fuel going into the exhaust. Catalytic converters can to a small degree reduce HC's, but too much fuel will ruin/plug them.

[SleeperT-Bird87]

Re: Emmisions help

What kind of test was it? The two speed dyno? I'm not conviced the timing is going to help your HC's and CO's. The CO's will drop with HC's, if you get the HC's below the limit and the CO's are still above you will need an Air/smog pump.

Were the NOx measured? That is what is usually efffected by timing and real-lean conditions. Not that it was asked, but mitigators for NOx are the EGR, Catalytic converters and Timing.

The HC's being high is just being plain rich on the cruise circuit, sounds like a de-jet is in order and hope the over lap in the cam isn't bad enough to make you still fail from raw fuel going into the exhaust. Catalytic converters can to a small degree reduce HC's, but too much fuel will ruin/plug them.

It was a 2 step idle test one at idle and the second at 2,500. no dyno's here they dont measure NOx

[SpiderGearsMan]

Re: Emmisions help

how long can you drive on a failed sticker ? get an alky carb and run it on methanol ? that is why we mess with 40+ old cars in emission states . or do like I do and run florida plates in NJ

[SleeperT-Bird87]

Re: Emmisions help

how long can you drive on a failed sticker ? get an alky carb and run it on methanol ? that is why we mess with 40+ old cars in emission states . or do like I do and run florida plates in NJ

30 days

[Brian Lohnes]

Re: Emmisions help

If you have access to methanol you can try tipping a few gallons into your tank with the gas that's in there. Snuck my car though that way several years ago.

Brian

[TheSilverBuick]

Re: Emmisions help

One trick is to pour two bottles of gasoline anti-freeze (ISO-Heet?) in the tank so the alcohol would burn cleaner, but honestly I don't think it could drop HC's even 50% (more like maybe 10-20%) but if you get it close it's another trick.

My thoughts are if you can lean it out with the jets best you can and use timing to keep it idleing and running proper, you're just plum rich.



I had to smog my Skylark practically every year in California (until I moved to Nevada) because it never passed on the first try and I had it fail for all the reasons from HC's, CO, NOx and visual. So after a few years I got a pretty good feel of what I had to do to mitigate each (including using a hotter spark plug on a cylinder that consumed a little oil). Hotter plugs if your engine can resist detonation with them would possibly help as well.

If your smog guy is a little lax on his inspection and your exhaust is loud "dilution" works too (i.e. holes/loose bolts in the exhaust)

I haven't seen Dan (he'll probably want to kill both of us) but I am a believer in being compliant, though there is no smog check here in Northern Nevada I plan on running two cat's and an electric air pump on my Skylark when I get the exhaust done properly just because I think the Hp loss at my 300-500hp levels is acceptable/minimal, but I don't do any professional/bracket racing.

[Silver68RT]

Re: Emmisions help

High CO and HC's are usually tied to running rich, but your AFR reads lean. Looking at your cam spec's, with that much overlap, I'd say you're getting poor combustion, slow burns, and misfires at idle - which would show up as a lean AFR that swings around a lot, and high emissions due to the unburned HC's and CO. It may just be too much cam to pass emissions. Have you got something milder you could throw in? That, and the stock-style distributor might help. Catalytic converters work best around 14.6:1 on gasoline. Get too far away fromthat and they don't work very well, and they don't do well if you're misfiring either.

[SleeperT-Bird87]

Re: Emmisions help

thanks for the input guys keep it coming.

I dont think the tester done me any favors either she put the probes in the pipes about 5 min before the test began and for the first time ever the done a high idle test (2,500) all my past test have been at idle.

[Silver68RT]

Re: Emmisions help

Might be worth getting or borrowing a wideband air-fuel meter, and see what your AFR is at that 2500 rpm point, if that's where you failed. If it's rich there, you could try leaning it out a bit.