Fuel Pressure is only a measurement of restriction in the fuel system and has very little to do with fuel VOLUME.
Sounds like you running a Holley Blue, thay actually will flow at about 75GPH at pressure, combine that with the Blue Reg which flows maybe 50GPH and you'll see that a good mechanical will out flow it. Holley Blue Systems, IMO are good for about 300 HP max.
There lot's of thing's that determine fuel requirements, let's analyze a few.
1. You have a 1/2 line, that's very good, but what size are the inlets and outlets on your pump? The answer of course is 3/8" so your pump will only flow at the rate allowed by the smallest orafice in the system, remember electric pumps are gravity fed so although the outlet side will flow more volume due to the pressure the inlet which is gravity fed is the limiting factor.
2. Let's use a 12 second flat car for an example. I would think we can all agree that this car would burn about 1/2 gallon of fuel to make a 1/4 mile pass. So if we do the simple math to determine GPH (Gallons Per Hour) 1/2 gallon x 5 (60 secs. / 12 sec pass = 5)= 2.5 gallons per minute x 60 minutes = 150 Gallons per hour, far beyond the capacity of a Holley Blue or any mechanical pump.
3. So we've determined how much fuel we need to make a pass and the capacity of the pump required. But what about the gear ratio in 1st of about 2.50? Does this have any affect? Of course, we all know from experience that a car will use way more fuel at 30 MPH in 1st than it will in 2 or high gear so we need to make allowances for the huge consumption in low and 2nd gear. Some of this is built into a Demon with the larger float bowls creating a built in reserve, but if the pump can't keep up the floats will drop and the carb will not be able to maintain a nice flat fuel curve as demand increases. Do you think that maybe 20% more fuel would be a fair number to use?...so we're now up to 150 + 20%= 180 GPH
4. Let's not forget G forces, does your fuel line run from the cell straight up the carb taking the sortest route possible? By running the fuel line in this manner you further complicate the G forces working against the pump, all the fuel in the line is pushing back against that pump and will actually stall the pump (Remember the main feed line from the tank to the pump it's going in the opposite direction also starving the pump of adaquate supply)
The correct way to plumb a car for optimum fuel delivery would be to have the main line come all the way to the front of the car, we run them through the radiator core support, a big loop and back to the regulator.. Now when the car launchs the fuel is driven by G forces to the regulator giving it a supply while the pump recovers from the shock. So if your running your lines in what is probably not the best location then I think a 10% increase in pump capacity should be built into the equation....180 + 10%= 200 GPH
(How's your fuel system holding up so far?)
5. I'll bet you have your regulator mounted to the engine or chassis right? Another No-No....as the engine starts to wind up and the car builds speed that regulator is getting the ever loving ***** rattled out of it. In allot of cases so violently that the spring can't hold the ball on the seat so it releases fuel and can overflow the float bowls. You've all seen this at the track...a car gets about 300' out and it starts leaving a black haze behind it.
6. Feeding the carb from the regulator is another consideration, if you running a dual feed line that uses a T and splits off to feed the bowls your probably OK to about 350 HP aafter that we reccommend to use a 2 port regulator and supply each bowl with a -6 line from seperate ports on the regulator. Thjese lines need to be as short as possible we use a 7.25" line with a 45* on one end and a straight on the other with the BG 2 port it works perfect. Too large of lines or too long of lines will cause the regulator to respond slowly as there's more fuel volume to drop in pressure and more volume to fill to get back to full pressure.
7. Weight consideration and engine size are another factor to look at. If this 12 second car is a 4000# Hemi Super Bee or a 350 SBC in a 2800# 67 Camaro? Again I think we can all agree that even though both of these cars may run 12's their fuel consumption will vary drastically so the rule of
12 second car requires a fuel system that can deliver 1 gallon in 30 seconds becomes a rule of thumb and not an absolute number.
In this scenario the Hemi Bee would probably need a BG 280 whereas the Camaro would have plenty of fuel with a BG 220.
Your Fuel System is just as important as choosing the correct cam, the right Carb, tuning the Ignition, selecting the correct tork convertor, compression ratio etc. it's all part of building a good dependable and consistant car whether it's a Street Muscle Car, Sunday Bracket Racer or a Top Comp/Pro Stocker you
must have an adaquate fuel supply to feed the power you've created, if you don't want to or can't afford to build an adaquate fuel system then don't build the power. Piston manufacturers love you guy's it keeps them in business.
I've been in this business for most of my life, been tuning carbs and ignition systems since a was a young kid, worked with my Dad who was probably one of the best tuners ever, he started teaching me this stuff when a was about 6-7 years old....that was about 45 years ago. But if I need a cam I call Jim at Racer Brown a real cam grinder, if I need a Convertor I call on Frank Lupo at Dynamic, when I need pistons I call Ronnie at Diamond, I use the experts available to me, I draw on their experience in their specific fields to obtain the best results. It works for us.....our All Iron, All Motor 318 Mopar in a 3100# car will crack off a 11.60 pass with 6200 RPM shift points anytime I hammer on it.
So in closing I can only strongly reccommend that if your not a expert on fuel systems then consult with someone who is and stop relying on a salesman at a mail order house or some rediculous magazine article to sway your decisions on your fuel system or ffor that matter any other component. Deal with that special individual who has risen to the top of his field and forget the mass producers of fancy catalogs and generic one size fits all components.
If you follow what everyone else does then you will follow everyone else, I prefer to lead, the view is much better up front ...Mush.....if you ain't the lead dog the view sucks..