I read the Berry K article (sticky), Lars papers and a few other fine write ups on timing and all are great information to have. Somewhere a comment was made to "find the timing your engine wants" which I thought was interesting since we all have different components in our build.
My engine is hard to start (when cold), runs a little rough at idle but runs very well above idle. I was thinking the initial timing might be a factor in the "hard to start" situation. Here is what I have;

1968 with 327 Came out of the factory with 300hp but is now between 350 and 375hp. (that's my guess)
10.5:1 CR ( no hint of detonation)
World Prod 042660 heads (2.02 / 1.60, 170CFM)
Edelbrock Torker II intake Single plane #5001
Edelbrock 600 CFM carb
Crane Z274-2 cam (473 / 486 lift, advertised duration 274 / 280)
HEI distributor

For the stock 327 / 300hp the book calls for 4 degrees BTDC initial timing.

Mine is set at 14 BTDC
If I drop the timing to 12 or lower it will backfire through the carb when I punch the throtle. So does this mean my engine likes 14 degrees base timing? Total timing is 36 degrees all in at 2800 RPM.

Is 14 degrees making it hard to start cold? I have to pump the gas about 6 - 8 times while turning the key to get it to start.

 

I don't think the timing is the issue. Sounds like your choke is not working or the carb is low on fuel after sitting. Could be fuel drain back, fuel evaporation, or the carb leaking the fuel into the intake after shut off.

 

My answer to you question is no. Usual sign of too much advance is it'll kick back at the starter when it's hot.
I'd say your backfire thru the carb when you jump on it is a lean accelerator shot. Late or not enough.
I'm running 18* initial, 41* total @ 3000, no vacuum. BB, 12.5 compression, and close to .600 lift cam.

 

You can check with some Start Pilot starting spray in the carb to see if it helps to start the engine when cold.
If it does you probably have a fuel issue. If you park your car with engine hot, some or most of the fuel in the carb will start boiling and evaporate.
If the carb bowls are almost empty, it takes some time with a mechanical fuel pump to fill them.
Your engine won't start until there is enough fuel in the bowls.

 

The real way to set this up is buy a carb jet kit, then bring it to a Dyno. They can dial both the carb and timing in to set the car up perfectly.

 

Idle quality is normally impacted by carb idle adjustments, by choke settings, and by vacuum leakages in your system. Make certain you don't have any vacuum leaks at idle; then make proper choke adjustments (per Chevrolet Chassis Service Manual instructions) and, finally, make proper carb idle adjustments (also per Chevy CSM). Until you've done those things, no further advice here will be of any help to you.

 

that sounds like a great set up on your mill and not to hi jack this thread but i think if you tried stronger springs on your mec adv so you are all in at 41 at 4000 instead of 3000 you might find better mid range performance..jmo i too dont run any vac adv and swear by the mech only method.....