Off idle flat spot

[jnick9900]

Thoughts... I just installed a edelbrock performer plus cam, set timing at 14° per the sheet. Runs good smooth.. ONLY barley of idle small flat spot then it kicks back in. Holley 650 cfm... Kind of off doesn't hamper much. but feel like the flat spot shouldn't be there. Whats your thoughts

 

[rich weyand]

You got your vacuum advance on ported vacuum? Move it to manifold vacuum.

Another potential cause: insufficient accelerator pump shot for high-vacuum engine.

 

[MikeB]

The timing is 14 degrees at idle with the vacuum advance line plugged, right?

And with the line still plugged, does the timing advance increase as you rev the engine?

Now, with the line connected to full manifold vacuum like Rich suggested, how much advance to you see at idle? That would be "initial plus vacuum".

A couple more questions:

What is your idle speed?

Have you adjusted the idle mixture screws for max vacuum? If so, is max vacuum at 1-2 turns CCW from fully seated?

 

[jnick9900]

Update

Off idle was what I noticed yesterday. Today it's about 2k and surges. Couple hundred rpm. I tried moving my vacum line and really haven't noticed much. Thinking of getting vacume gauge and adjusting carb? Right now the screws are at 1 1/2 turn

 

[jnick9900]

also

i have the sure weather the vac advance is hooked up to either port or not at all still surges