Horrible Idle on a holley 800..
 

I cant get the idle correct on my 800 double pumper..its extremely rich at idle. Like to the point when it almost dies. I have replaced the power valve, I have reset the air/fuel mixture to 1.5 turns from seated. Any sugestions??

air bleeds plugged ??? Fairly common problem
How about the needles seats float level. .. Bleeding over.

how much fuel pressure do you have?

6 pounds. .it idled fine one weekend..then the next Hard to start and bad idle..

Sounds like varnish got loose and plugged some passages . Carb cleaner and blow out all passages , bleeds and jets good should cure it .

Take the idle mixture screws out and use the wand on your carb cleaner and press it directly against the air bleeds. Send a bunch of it through there. Then follow up with some air, reinstall the screws, and give it a try.

When we ran my 489 on the dyno with my 800 on it the first thing their carb guy noticed was that it was running very rich at idle. He ended up having to slightly drill out the low speed air bleeds to lean it out at idle. Did the trick - took it from 11.8 at idle to about 13.9, IIRC.