383 Wont Idle with new to me 800cfm DP. Idles and runs ok with Edelbrock/AFB

340dartley said

I slower turn the idle screw back until it gets to the idle circuit and it dies. I have adjusted the idle mixture screws out up to 4 turns and no change. I am thinking maybe power valve is set for too high of vacuole and maybe my 7 to 8 inches of vac is causing it to dump. I did not see any vacuum leaks. I have since removed it and put the Edelbrock back on and it is back to running normal. Is this a case where drilling holes in the throttle plates is in order? Thanks for the replies.

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I slower turn the idle screw back until it gets to the idle circuit and it dies.
It was on the 'idle circuit' the whole time. (At 1800 rpm really unlikely the boosters started up. But you can look. ) The 'idle circuit' supplies fuel above idle. The idle ports are only a branch of that circuit.
I have adjusted the idle mixture screws out up to 4 turns and no change
Not surprising they lose effect above 2.5 turns out or so. What happened when you ran the screws in?
If you want to give it another try, set the transfer slot as mentioned above. WRITE DOWN how many turns of the idle stop screw it takes to reveal .020. .030 and .040 of the transfer slot.
When on the engine, it should be no more than .040 once its warmed up.
What's the initial timing at? 800 rpm? 1000 rpm? 1200 rpm, 1800 rpm? Within reason you can pickup some rpm by increasing the timing. Going to guess it will want at least 16* and will probably like 18* initial better, maybe as much as 20.
Is this a case where drilling holes in the throttle plates is in order?
Yes. But it seems too far off and too little info to jump to concluding that's what is needed.