Interpretation of Smog Test Results

[Big O Dave]

I just had my '76 Chevy C20 (350 V8) smogged and I was wondering if anyone around here has the expertise to interpret the results, in terms of engine condition and tuning. Here are the results:

A. Idle (714 rpm)
%CO2 (MEAS): 11.2
%02 (MEAS): 5.0
HC (PPM): MAX 250/AVE 57/MEAS 41
CO (%): MAX 1.50/AVE 0.70/MEAS 0.11
RESULTS: PASS

B. 2500 RPM (2591 rpm)
%CO2 (MEAS): 11.2
%02 (MEAS): 5.2
HC (PPM): MAX 200/AVE 33/MEAS 17
CO (%): MAX 1.60/AVE 0.30/MEAS 0.08
RESULTS: PASS

Thanks in advance!

 

[bamorris2]

Here's my interpretation of your results: YOU PASSED!!!

 

[paulo57509]

You passed so there's not much interpretation to do. However, I would say that you passed easily and should continue to do so.

 

[surfstar]

I thought the CA cutoff was 30 years for smog exemption?

You passed so you're in good shape and tune.

 

[bamorris2]

Quote:

---

I thought the CA cutoff was 30 years for smog exemption?

You passed so you're in good shape and tune.

---

From Ca's DMV website:

Does my vehicle qualify for a smog exemption?

Smog inspections are required unless your vehicle is:

Hybrid
1975 year model or older
Diesel powered
Electric
Natural gas powered and has a Gross Vehicle Weight rating of 14,001 lbs. or more.
Motorcycle
Trailer

 

[tom slick]

Read these articles on emissions
http://www.autoshop101.com/forms/h55.pdf
http://www.autoshop101.com/forms/h56.pdf

from
http://www.autoshop101.com/

 

[kc8adu]

seeing the readings are way below the averages listed its in great shape and near perfect tune.

 

[Big O Dave]

Tom, you hit the nail on the head... those links are EXACTLY what I have been looking for... thanks!

 

[1sttruck]

You really need a trend. The 93 Taurus had very low readings for years and then the HC values started creeping up when it had over 100k miles, but were still well below average. By about 170k or 180k miles I ended up replacing some fuel injectors, as I couldn't find anything else that might be causuing a starting and driving problem, even though the injectors tested ok. Pulling the manifold I noticed that some injectors had a very different spray pattern, it was bigger, which to me suggested that they were just worn out. With the new injectors the car started drove fine again, but the tranny died (at about 210k miles)before I had to have it smogged again.

I suspect that the bad injectors had also caused more cyclinder wear, as oil consumption started going up around something like 150 or 160 miles. As a result I'll plan on replacing the fuel injectors in the other two Taurii and in son's F150 sometime after 120k or so miles.