I recently got my 68 Coronet running and now I need to pass emissions here in Arizona.
The motor is a 318,(probably original) with X heads,Offy dual plane intake,Edelbrock 1406 carb,and headers.
The vaccum advance is disconnected at the distributor and all vaccum ports on the carb are plugged.
Except for the new carb this is the setup that the car had when I bought it.
It has a automatic trans.
What I don't know is if the motor has 68 stock internals, ie; pistons, cam etc.
In this county you must pass emissions to register the car.
Any advice would be greatly appreciated........

If I remember in Vegas was the max idle rpm was 1,200. It'd be best to try and idle it up as close as you can to help clean it up. Also leaning out the mixture some as well. Is it just a sniffer? dyno?

Smogging a '68 is asinine! Let's spend that money on illegal immigration.

Thanks for the reply.
They use the probes in the tail pipe and run it on the dyno.
How should i lean out the mixture?

1)Pray you have something close to a stock cam.
2)As Goody stated, raise your idle to something in the 1000-1100 range (you may want to check on max allowable first, I think states vary)
3) Retard your timing! You want something in the 2-6 BTDC at idle--this can help big time
4) Lean the carb a bit but be careful--too much and you'll increase CO emmisions
5) Clean air filter--or NO air filter
6) Fresh oil change (it helps a bit)
7) An alcohol fuel mixture (at least 10%, you can increase it with gas line antifreeze in a nearly empty tank)
8) Make sure engine is warm, coolant temp should be at least 190

I agree smogging a 68 is insane

Here's the max allowable hydrocarbons (hc) in ppm : 260 (loaded)
Carbon monoxide (co) in % : 3.89

When I retard the timing a couple of degrees the idle drops (as to be expected).
The vaccum reads 10 in. hc.
the more retarded the timing the less vaccum, correct ????

run the tank down to about 1/4 and add 1 to 2 gal of methanol, if you add to much it run like crap, if that happens add about another gal of gas..

and it will pass the sniffer test.. then go fill the tank up asap.

An msd box will help a buch with the lower rpm portion of the test if you have any sort of cam in it.

The air screws on the carburetor make a big difference. Finding the sweet spot can be tricky if you have an engine that is borderline on passing. You can always take it to a service station and have them set it up for you with their equipment and then take it back and get it tested.

If all else fails buy some catalytic convertors without the air tube and splice them in as far forward as you can.

Testing old cars is a money grab if you ask me. Sure they pollute more than new ones, but the amount of time they spend on the road is very small. Most people drive them a few times a month in the summer to go to car shows and thats about it.

I checked the timing before changing anything and it read 16 to 17 degrees btdc. I retarded it to about 12 and turned up the idle a little. It seems to have a rougher idle at this point.
The vaccum is reading 9..........

If you have not had it tested yet do that first, but get the engine tuned up and running smooth. Get some base numbers to start with first before you start chasing a problem that may or may not exist yet.

https://board.moparts.org/ubbthreads/show...e=1#Post4446839

Thanks for all the replies.
I was hoping to pass on the first test !
Are my settings close enough to go try it ?

I would set the timing to stock and make sure it has new plugs, plug wires, pvc, oil, air filter etc. and then test it.

Thanks.
I'll post the results later today........

Put classic car insurance on it and you don't have to pass emissions anymore!!

I thought only cars after 74 had to be sniffed. That's the way it is in NM.

In AZ it is 67 and newer unless it is on a classic car insurance and NOT a daily driver.