How to Tune for emissions?

My bro has a 83 cutty with a olds 350 and a edelbrock 600cfm carb on it. I just had two 2.5 cats installed and we went and had it sniffed, it failed HC with 475 and Co with a 10.x. Here is where the car was tune wise

idle 525
temp 220
The timing was advanced far enough to run on 89 without pinging.

I am thinking that timing should be retarded like I do with my LT1 to lower the HC but an old timer told me carbs run cleanest advaced, Which is it?
I have also raised the idle to 650-700. I retarded it by ear since I dont have a timing light, I backed it off till it stumbled and then added a hair. My old timer buddy told me to also run in the mixture screws until t stumbles then back them off slightly.

So my two questions are do I retard or advance and is he right on the mixture screws? Thanks guys, carb tuning is an art in which LT1 edit cant teach me.
:bow:

To reduce knock of pinging you have to retard the timing not advance it.
But as far as the rest you appear to be on the right track. In general you want the engine as lean as possible. So screwing in the idle screws and raising the idle should help. Also make sure the tune up is fresh, new plug and all that. Make sure it's hot and that the coke is full open and the EGR is closed.
Good luck.

Well I did better but still failed, temp was around 235, glad it has synthic in it. I had retarded the timing, put 6 bottles of dry gas in it, raised the park idle to 775, and screwed in the mixture screws until the idle dropped and back them out a hair. The new results are 110 HC, pass, and 5.6 CO, fail. Old was 475 hc and 10.6CO. Do I need to try to retard it more, I am thinking about some advance now. BTW when the engine was hot the idle made its way up to 1000, I set it at 800 when the temp was 210, what gives, why did it go up with heat. :confused: Higher is better anyways but I need suggestions on timing.

You might want to check the state law. Most state offer you an out, if you can't meet the standard with an older car. Like after you have spent X amount of money you get a waver.

sounds like a nice idea but we dont have that here, I know it can be tuned to pass anyways. I just need some bacic idea on how to get there.

LOL yeah retard it some more, we have that X spent amount here in Canada, British Columbia but its like $600 LOL after that money it better pass.