I have a 427 big block that is pretty well built with 650 to 715 estimated horsepower at the flywheel. This is primarily going to be a street car. Right now I have an aluminum weiand high volume mechanical water pump and a Holley 110 GPH mechanical Fuel pump. What are some of the main advantages to running electrical fuel and water vs mechanical? I have heard that with big blocks they can really drain your battery but do free up horsepower.  

They do free up some power. But being a big block has nothing to due with the drain on your battery. The drain on your battery will come from the elecrtrical draw of the motor. Some fuel and water pumps just use more juice to flow what other ones can do with less juice. Its all in the brand name and quality (and price). If you are using an older style alternater (60-70 amps with 15-20 amps at idle) it may put a load on your charging system. Jump up to a newer alt. or aftermarket one that can put out 70 plus amps at idle. Electric water pumps free up lots of power due to you have to run an electric fan as well. Most run at a fixed rpm like 2000. This helps cooling at idle. Not to mention they have more gallons per hour which sometimes is needed. An electric fuel pump will free up power but not a great deal more. The main advantages are  even consistant fuel flow at all rpms, more fuel flow, and the ability to keep the gas lines away from the motor to reduce heat. I dont think your 110 fuel pump will feed 700 horsepower. That holley pump has 3/8 fuel lines which is way to small to feed the amount of fuel you need. Call up or e-mail  a good company like summit or holley and they will put you on the right path. The disadvantage of elecrtic pumps is just that "there electric". They normally do not last as long as mechanical. Although I have great luck with them on the long term. If you run a electric water pump on the street be safe and hook up a warnning light that will go off when your temp gets hot. You will see the warnning light before you notice your temp gauge. That is cheap $50 insurance on a very costly motor.  This is just a ball park idea of how much more power you can gain (and I'm sure someone will disagree).  Electric fuel pump 5-10 hp. electric fan 10-20h.p  electric water pump 5-10 below 4000 rpms and 10-15 maybe 10-20 above 4000 rpms.   By the way what is this big power house 427 going in???  

I already have an electric fan with a custom fitteds hrowd with an aluminum radiator and 100 am power master alternator. Here is my currect full set up

WHEELS & TIRES:
Center Line Auto Drag Pro Street Wheels Front: 15x6 and Rear 15x14.5
Goodyear Front Runner Tires (Front)
Hoosier Quick Time D.O.T. Tires 31x16.5x15 (Rear)

TRANSMISSION:
Muncie 4-Speed Transmission
Cincy Driveline Custom Driveshaft
Zoom Stage 3 Multi-Friction Clutch
Hurst Competition plus Shifter

ENGINE:
1969 Corvette 427 BBC Engine Block
Moroso High Volume Oil Pump and Pickup Kit
Moroso Street/Strip Oil Pan
Edelbrock Victor Jr. Aluminum Heads
Manley Stainless Steel Valves
Grantenelli Fabricated Aluminum Valve Covers
Weiand Hi-Ram Tunnel Ram Intake
Holley 600 CFM Carburetors
Eagle Forged Steel Crank
Clevite 77 Bearings
GM Performance Parts Harmonic Balancer
Pete Jackson Gear Drive Noisy
Mr. Gasket Chrome Timing Cover
Eagle Forged I-Beam Connecting Rods
Speed Pro 11:1 Forged Pistons
Comp Cams Thumper Roller Camshaft
Comp Cams Magnum Hydraulic Roller Lifters
Comp Cams Magnum Hydraulic Push Rods
Harland Sharp Roller Rockers
Weiand Alumninum High Flow Water Pump
Specter Billet Pulleys
Be Cool Aluminum Radiator with Electric Fan and Aluminum Shroud
Spectre Wire Plug Wire Loom
Mr. Gasket Injector Style Street Scoop
ARP Studs and Bolts

IGNITION & ELECTRICAL
MSD Pro Billet Distributor
MSD Blaster 2 Coil
MSD 6 AL Ignition Box
MSD Super Conductor Plug Wires
Jegs Chrome High power starter
Power master GM 100 Amp Chrome alternator
Optima Red Top Battery

POWER ADDERS:
NOS Cheater Nitrous System 250 Shot
NOS Purge Kit

REAR END &SUSPENSION
Richmond 4.11 Gear
Auburn Gear Limited Slip Differential
Moser Axles
Competition Engineering Full Ladder Bar Suspension
QA1 Front Coil-Overs and springs
Competition Engineering Rear Coil-Overs
QA1 2 ½” I.D. Coil Springs

BRAKES:
SSBC Front Disc Brakes
Wilwood Master Cylinder
SSBC Dual Diaphragm 7” Chrome Booster

FUEL& HOSES:
Holley Mechanical 110 GPH Fuel Pump
RCI Pro Street 16 Gallon Fuel Cell with foam
Spectre Steel Braided Hoses with anodized fittings

EXHAUST:
Headman Ceramic Coated Headers
Jegs 3 ½” Exhaust Turndowns

INTERIOR:
Auto Meter Pro Comp Tachometer W/shift Light
Auto Meter Pro Comp 200 mph speedometer
Auto Meter Pro Comp Oil Gauge
Auto Meter Pro Comp Fuel Gauge
Auto Meter Pro Comp Water Gauge
Auto Meter Pro Comp Volt Gauge
Auto Meter Pro Comp Nitrous Pressure Gauge
Moroso Switch Panel
Painless Wiring Fuse Box and Harness
RCI 5-Point Racing Harnesses
Kirkey Aluminum Pro Street Style Seats
Grant Billet Steering Wheel
Jegs Aluminum Interior kit and Dashboard
Competition Engineering Steel 8-point Roll cage  

I have two different opinions on this. On the fuel pump side, an electric isn't a bad thing necessarily, and when it quits, you know about it without any risk of damage to your motor. They can also move more fuel and can be mounted back by the tank for better fuel delivery.

On the water pump side, I do not like electric pumps outside a drag racing application. For a street car, if your electric water pump quits, you have no way of knowing until the motor starts overheating, which introduces the risk of engine damage. On the mechanical pump, you start seeing those drips from the weep holes, time to change the water pump, and you won't risk melting the motor.

The parasitic HP loss to me is insignificant comapred to the reliability and safety issue.  

Yeah you make a great point actually.  

Aside from the great input from '55 Guy,' mechanical water pumps do a better job of cooling at lower engine speeds. This makes them even more suited for a street application. The horsepower loss is minor, especially if the mechanical pump is underdriven...

The reason that electric pumps don't cool as well as mechanical pumps at low speeds involves the fact that almost all electric pumps on the market only run at one speed whereas the mechanical varies with engine speed. With electric pumps the situation arises where at low speeds the water is traveling faster than ideally to soak up all the heat present. Thus the reason why low-speed cooling can be sacrificed. The price of electric water pumps don't help the situation either...

Electric fuel pumps are a given for most applications. Traditional mechanical pumps (like that would find on a SBC Chevy 30 years ago) don't have the capacity the feed power ranges well above stock. Also, a mechanical pump is just a less efficient way of delivering the fuel as it must create a large vacuum to draw fuel from the tank. This vacuum only adds heat and increases the tendency of the engine to vapor lock. Only on very high-end applications (like maybe 650+ horsepower on some sort of Alcohol) would a mechanical pump be considered but these would not be driven by a pushrod but rather a gear or belt and might have a small electric pump pushing fuel to them from the tank.

Hopefully that covers a lot of applications that may be included in your question.  

Yeah it helps alot actually. I may look into getting the 140 gph holley black series electric fuel pump and just keep my water pump I have now