Carb size, Hmmm. Let me see if I can break this down.

429 cu.in.
Bore 4.36 x stroke 3.59
Bore x bore x stroke x .7854 x # of cylinders
4.36 x 4.36 x 3.59 x .7854 x 8 = 428.7836 cu.in.
However, you have an overbore of .030, SO
4.36 + .030 = 4.39 bore, SO
4.39 x 4.39 x 3.59 x .7854 x 8 = 434.714 cu.in

HOW TO FIGURE CARB SIZE ( NOTE: Most guys tend to OVER carburet )

434 cu.in. Divided by 2 = 217.357
Don't know the top RPM of your cam but (sample 5,500 RPM) SO
5,500 divided by 1728 = 3.182
Giving the info above =
217.357 x 3.182 = 691.620 CFM (ASSUMING 100% EFFICIENCY)
However, most things don't operate at 100% - more like 80%.
Since you say you have added a cam, headers and Edelbrock intake. lets put it at 90%. That may be pushing it, BUT

692.620 x .9 = 622.458 CFM

All-in-All, a properly tuned 750 CFM Holley carb will most likely cover your needs for now and in the future should you add a BIG cam and valves. It's all about 'flow'.

Sorry for all the techno garbage but this is how it works.......... ;o)

 

Im running 2 3/4 exhaust with a H pipe out dual flow master 40's. mid range power feels strong its when i first put the pedal down it seems to be staving for gas. Fuel comes thru a new edelbrock fuel pump. im running on 93 octane. im also playing with the timing alittle. but if i advance it alittle it runs good but then starting it when warm becomes an issue.

 

Few question here and I'll bet you will get many of the guys to chime in real soon...
Header, 3.75 pipes, FM - well, flow from the motor is good.

1. Why are you running 93 oct ...?
2. Are you saying that when you start it up, it hesitates...? Hiccup's...?

1. Unless your cam is way out there or someone has REALLY reworked those heads, I see no need to use 93.
Really need the stats on the cam.
What is the CR. Do you know anything about the pistons ? Have you done a compression test. These can also make a decision on what fuel to use or where your timing should be set.

2. If it is too advanced, it will have a hard time starting.
Try this.
- back off the advance so it starts up ok.
- start the motor, reave it up to about 4500 rpm and hold it there.
- advance the timing until it starts to stumble. When it starts to stumble, back it off, just past the point where it stops.
- lock down the distributor. The motor should at this point, start up easy. That is if it is indeed retarded from where it was. If everything in the distributor is operating correctly and your vacuum advance is hooked up correctly, it should function half way decent.
Take it out on the road. Check for quick response off the line. Check to make sure at full throttle, it does not ping. If it pings, you are still too far advanced. Problem for ping could be inside the distributor.

REMEMBER, this is only a 'seat of the pants' way to adjust the timing and will in most cases, get you down the road until other things can be checked. Right after you do this procedure, grab a timing light and check to see where it is on the wheel. That will be interesting. This will get to close to where the factory specs say it should be...

IF it does not, there are things you need to check to have done.
1. you will need to make sure your HB timing has not slipped on the balancer - you will need to find TDC and mark that on the wheel. If it has not slipped, Good.
2. If indeed your vacuum is hooked up correctly and it is still giving you a problem, you may need a good distributor guy to set it up for you. Some of the guys that do this kind of work are incredible.

Hope some of this helps.