1980 720 failed emissions... Not sure what else I can do.

[Dylan Berichon]

What was your timing at idle? I had this issue last year, except my CO was fine and HC was high. CO is A/F mixture, and you can set this to lean best idle with a vacuum gauge. HC, as stated, is usually ignition, as it was in my case. The advance centrifugal advance in my distributor was hung up in an advanced position. My initial timing was 25 degrees BTDC. Ran great, except it pinged and smelled like a BBQ grill. Get the carb to where it idles alright, THEN recheck the timing, THEN go back to the carb.

 

I'm not sure what the exact timing setting was.  I've always set timing "by ear" to where a car (or truck, in this case) just stops pinging.

 

I can put a light on it and see what it says.

[smoke]

While it is your carb having the issue here, having your timing too advanced at idle will cause you to fail. 

[Buzzbomb]

If I was you, I'd get that new carb on, get it set up, and set it to 12 BTDC. That's the factory spec for our truck, and you WILL pass HC with flying colors barring some other unknown issue. As I said, my timing was 25 BTDC and I was pulling 550 or so HC, and when I changed my distributor and the timing wasn't over advanced, it went down to around 125 or so. You can still be over advanced by using the ear method, you really should set it by light, IMHO. At 25 BTDC, mine just barely pinged going up a hill, and if I backed off to 20 with no ping, it still probably would have failed.

[devilsbullet]

Easy fix. Move across the river to Vancouver. Anything over 25 years doesn't need emissions

[datzenmike]

Really dirty air filter?

[ggzilla]

Dylan, since your carb's mixture screw does nothing, you won't be able to adjust the idle CO and HC.

 

Its really rare to have a do-nothing mixture screw and a (correct) 800 rpm idle speed. I cannot think of what can cause that. Maybe the tip of the mixture screw is damaged.

[Dylan Berichon]

Hi All!

 

So, to make a long story short, the vendor I ordered the carburetor from cancelled my order.

 

I went ahead and ordered a Weber carburetor through my work.

 

I have access to TONS of jets (we sell Weber conversion kits for antique Volvos that also use 2.0 liter motors) so I'm certain I'll be able to track down whatever I need to make this thing run correctly.

 

Any suggestions for initial jets to try?

 

 

Thanks again for all the input.  I only need to pass the idle test here in Oregon, so I think the Weber will get the job done.  

 

I'm hoping so, anyway.

[WI 720]

Sounds like the new carb is the right way to go.

If you want to try to tip the balance in your favor, you could get new spark plus, new air filter, do a synthetic oil change (I use Amsoil or O'Reillys store brand). You could also try a fuel system cleaner. Archoil makes some good stuff.

[Dylan Berichon]

Hi All!

 

I know this is an old thread, but I thought I'd just update those that were curious.  I got the Weber installed this past weekend and got the truck through the emissions test.  It passed with flying colours!

 

Thanks again for all the input here!  It is greatly appreciated.

[Gradyfest]

Congrats on passing smog! And thanks for the update, so many just leave people in suspense hanging. Do you got photos of this beast anywhere yet?

[Charlie69]

2 pages and no pictures!

[arizonajones]

Good thread. I've been wondering for a long time if anybody in Portland had passed emissions with a Weber. Let us know if you have any recommendations on jets or anything.

[Tinman]

Was wondering what the outcome of this was.

 

Too bad we can't do this in Kalifornia.  I drove a weber equipped 720 and loved it, but the guy was desperate to sell it because he couldn't register it here.