Passing CA Smog help - High HCs

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

77Matt

Member
Joined
Mar 21, 2024
Posts
49
Reaction score
26
Location
TO, CA
First Name
Matt
Truck Year
1977
Truck Model
C15
Engine Size
5.7L 350 V8
I had my original electric carburetor rebuilt, i was told that was the only option.
Edelbrock says it’s street legal in 50 states- I don’t know when they were officially approved. I had to buy about 10 other parts to make it compatible thought. Just hope it works
 

Attachments

  • IMG_7725.jpeg
    IMG_7725.jpeg
    85.3 KB · Views: 29

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,446
Reaction score
8,679
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
Edelbrock says it’s street legal in 50 states- I don’t know when they were officially approved. I had to buy about 10 other parts to make it compatible thought. Just hope it works
His was a feedback carb. That's the problem,and to the best of my knowledge ccc carbs on trucks were CA. only
 
Last edited:

CalSgt

Full Access Member
Joined
Oct 3, 2021
Posts
1,699
Reaction score
3,761
Location
CA
First Name
Casey
Truck Year
1980
Truck Model
Chevy K-10 Custom Deluxe
Engine Size
350

Hoody

Junior Member
Joined
Oct 13, 2022
Posts
2
Reaction score
1
Location
Cali
First Name
Hood
Truck Year
1975
Truck Model
K25
Engine Size
350
I'm so glad my K25 is a '75 so no smog needed. I didn't read the whole thread but you might want to look into registering in SD or MT to avoid all this work, time and money just for ca smog. Check out Pennington County, SD Treasurer's site. For MT you create an asset holding llc and is more legit to reg in a business name plus its permanent reg no renewal. Can do it yourself or use a service like dirtlegal.com.
 

tsgs84

Junior Member
Joined
Jun 8, 2022
Posts
26
Reaction score
21
Location
md
First Name
Timothy
Truck Year
84
Truck Model
K10
Engine Size
350
I have a 1977 GMC 5.7L 350 given to me from my dad. It passed smog no problem less than a year ago for the title transfer. Now, it failed CA smog due to high hydrocarbons (3485 ppm @ 15MPH and 1350 @ 25MPH). Also noteworthy is that the technician said the crankcase ventilation hose that feeds into the air cleaner was disconnected (it must have popped off during the inspection). I fixed the PC hose, replaced the air filter, PCV valve, plugs and wires, and rebuilt the quadrajet carb. I was going to tune it to run lean perhaps before the test. I was also going to add the emissions cleaner (not sure if the is just snake oil). It's a project truck that I'm just starting but I need it to pass smog to get moving legally. Should I do anything else before taking it back in considering its almost 100$ each test (no free retests)? and no, moving is not an option lol.
Put good fuel in it, let it run low then load up on isopropyl alcohol (dry gas) on the way to the test. Worked every time for me. Considering that you have no major problems.
 

K5ride

Full Access Member
Joined
May 2, 2018
Posts
135
Reaction score
205
Location
Apple Valley, CA
First Name
Steve
Truck Year
1975
Truck Model
C10 Stepside
Engine Size
350
High hydrocarbons is caused by a misfire. It is unburned fuel. Check anything that would cause a misfire like tune up stuff, over advanced timing, lean fuel mixture, etc. Is your test the two speed idle test or on the BAR 97 dyno? If your GVWR for that year is over 6001 lbs, it is considered heavy duty and a catalytic converter is not required. It will also fail the visual portion of the test, if you add a converter on. You are not allowed to invent your own emission configuration. Driving the vehicle excessively or preconditioning only works for heating up the converter which does not apply to you. It is also not allowed if your smog tech is following proper procedures. Retarding the timing will lower hydrocarbons but you are only allowed +/- 3* from the factory spec at the designated rpm. I would be happy to answer any questions I can. I've been licensed for both smog check and repair in California since 1994 and make these types of repairs daily.
 

77Matt

Member
Joined
Mar 21, 2024
Posts
49
Reaction score
26
Location
TO, CA
First Name
Matt
Truck Year
1977
Truck Model
C15
Engine Size
5.7L 350 V8
High hydrocarbons is caused by a misfire. It is unburned fuel. Check anything that would cause a misfire like tune up stuff, over advanced timing, lean fuel mixture, etc. Is your test the two speed idle test or on the BAR 97 dyno? If your GVWR for that year is over 6001 lbs, it is considered heavy duty and a catalytic converter is not required. It will also fail the visual portion of the test, if you add a converter on. You are not allowed to invent your own emission configuration. Driving the vehicle excessively or preconditioning only works for heating up the converter which does not apply to you. It is also not allowed if your smog tech is following proper procedures. Retarding the timing will lower hydrocarbons but you are only allowed +/- 3* from the factory spec at the designated rpm. I would be happy to answer any questions I can. I've been licensed for both smog check and repair in California since 1994 and make these types of repairs daily.
Thanks - interesting that I can’t just add cats. And yes it is heavy duty. I retarded the timing only by 2 because that is the max now. I’m not sure what the machine was but it was multiple speed test. I changed plus and wires, swapped to a different CARB compliant carb. New air filter and changed oil. There is no egr because of the heavy duty status. Checked all the vacuum lines. I think I’m pretty much ready for to retest once I get the new carb tuned.
 

77Matt

Member
Joined
Mar 21, 2024
Posts
49
Reaction score
26
Location
TO, CA
First Name
Matt
Truck Year
1977
Truck Model
C15
Engine Size
5.7L 350 V8
High hydrocarbons is caused by a misfire. It is unburned fuel. Check anything that would cause a misfire like tune up stuff, over advanced timing, lean fuel mixture, etc. Is your test the two speed idle test or on the BAR 97 dyno? If your GVWR for that year is over 6001 lbs, it is considered heavy duty and a catalytic converter is not required. It will also fail the visual portion of the test, if you add a converter on. You are not allowed to invent your own emission configuration. Driving the vehicle excessively or preconditioning only works for heating up the converter which does not apply to you. It is also not allowed if your smog tech is following proper procedures. Retarding the timing will lower hydrocarbons but you are only allowed +/- 3* from the factory spec at the designated rpm. I would be happy to answer any questions I can. I've been licensed for both smog check and repair in California since 1994 and make these types of repairs daily.
Do you think that a disconnected pcv hose, the one from the valve cover to the air cleaner, could cause such a large amount of HCs? >3000 ppm
 

K5ride

Full Access Member
Joined
May 2, 2018
Posts
135
Reaction score
205
Location
Apple Valley, CA
First Name
Steve
Truck Year
1975
Truck Model
C10 Stepside
Engine Size
350
The breather hose to the air cleaner would not raise HC. The PCV valve to manifold vacuum would. As far as the timing, you are allowed +/- 3* unless the underhood label states otherwise. Here is a quote from page 18 of the smog check manual - "Pass/Fail Criteria: To pass inspection, the base ignition timing must be within 3 degrees (± 3 degrees) of the manufacturer specification. If it is more than 3 degrees from manufacturer specification, the vehicle shall fail the functional test. Note: If the manufacturer specification provides a range, the 3 degree additional tolerance described above is not allowed. "
 
Joined
Mar 21, 2024
Posts
52
Reaction score
187
Location
No
First Name
No
Truck Year
No
Truck Model
No
Engine Size
No
Y'all know way too much about smog compliance. Thanks to reading this thread I know more than I ever wanted to know now and I'm almost ashamed to be on the edge of my seat wondering if you'll pass. I know you said moving isn't an option but I would still, just move. 'Murica.
 

JBswth

Full Access Member
Joined
Jan 24, 2022
Posts
225
Reaction score
182
Location
Vallejo, California
First Name
James
Truck Year
1973
Truck Model
C25
Engine Size
292 cubic inches
I have a 1977 GMC 5.7L 350 given to me from my dad. It passed smog no problem less than a year ago for the title transfer. Now, it failed CA smog due to high hydrocarbons (3485 ppm @ 15MPH and 1350 @ 25MPH). Also noteworthy is that the technician said the crankcase ventilation hose that feeds into the air cleaner was disconnected (it must have popped off during the inspection). I fixed the PC hose, replaced the air filter, PCV valve, plugs and wires, and rebuilt the quadrajet carb. I was going to tune it to run lean perhaps before the test. I was also going to add the emissions cleaner (not sure if the is just snake oil). It's a project truck that I'm just starting but I need it to pass smog to get moving legally. Should I do anything else before taking it back in considering its almost 100$ each test (no free retests)? and no, moving is not an option lol.
I would do those things, then have a PRE-CHECK. That way if it flunks, you won't have to worry about them labeling it a Gross Polluter. When a vehicle is labeled a Gross Polluter, you will have to bring it to a repair only facility and have THEM fix it no matter how expensive it is, then, I have heard, bring it to a state smog referee to be smog checked. If you have a pre-check and it fails, and they tell you what is wrong, you can fix it yourself.

J.B.
 

77Matt

Member
Joined
Mar 21, 2024
Posts
49
Reaction score
26
Location
TO, CA
First Name
Matt
Truck Year
1977
Truck Model
C15
Engine Size
5.7L 350 V8
I would do those things, then have a PRE-CHECK. That way if it flunks, you won't have to worry about them labeling it a Gross Polluter. When a vehicle is labeled a Gross Polluter, you will have to bring it to a repair only facility and have THEM fix it no matter how expensive it is, then, I have heard, bring it to a state smog referee to be smog checked. If you have a pre-check and it fails, and they tell you what is wrong, you can fix it yourself.

J.B.
According to the smog report it was already labeled gross polluter but no one has said anything about where to get it repaired. I did all the repairs myself.
 

77Matt

Member
Joined
Mar 21, 2024
Posts
49
Reaction score
26
Location
TO, CA
First Name
Matt
Truck Year
1977
Truck Model
C15
Engine Size
5.7L 350 V8
Y'all know way too much about smog compliance. Thanks to reading this thread I know more than I ever wanted to know now and I'm almost ashamed to be on the edge of my seat wondering if you'll pass. I know you said moving isn't an option but I would still, just move. 'Murica.
I’ll keep you posted haha
 

DoubleDingo

Full Access Member
Joined
Jul 3, 2012
Posts
11,250
Reaction score
17,174
Location
Right where I am
First Name
Bagoomba
Truck Year
1981
Truck Model
81-C20 Silverado Camper Special-TH400-4.10s
Engine Size
Carb'ed Vortec 350
According to the smog report it was already labeled gross polluter but no one has said anything about where to get it repaired. I did all the repairs myself.
I think they do that on purpose. Mine shows up as a gross polluter as well, and there has never been any mention of it needing to be fixed by a shop. There is nothing to fix anyhow, everything works, it's just an old truck that stinks to high heaven of exhaust fumes no matter how well it is tuned.
 

Latest posts

Forum statistics

Threads
44,157
Posts
950,592
Members
36,271
Latest member
jstewart7501
Top