Need some help figuring out how many gph fuel pump I need.
It is for my 79 Camaro 350 .020" over, dual plane intake with a 4bbl 650cfm holley carb.

 

Small. If your betting a mechanical then a stock pump would probably do. I can't do brake specific fuel consumption math but my best guess is about 80gph. Most likely less.
Summit Racing SUM-250000-1 - Summit Racing® Mechanical Fuel Pumps - Overview - SummitRacing.com

A electric pump like this will do as well. 105gph.

Holley 12-801-1 - Holley Red Electric Fuel Pumps - Overview - SummitRacing.com

My 355 in my Nova went 9.97@135 with a Holley Blue rated at 110gph. It was also running the nitrous. Like I said I'd bet a good stock replacement for a 79 Z would be fine.

 

On a naturally aspirated engine, a BSFC of around .5 lbs. per h.p. per hour can be considered pretty typical.
300 h.p. (as an example) x .5 = 150 lbs. of gas per hour.
Gas weighs a hair over 6 lbs/gallon. 150/6 = 25 gph.

 

lol I was way off. I will have to keep that formula. Am I correct in saying the advertised flow rate is free flow and would drop considerably when you start adding fittings and lengths of hose?

 

But bigger is better, right? lol
Now say you had a supercharged engine, your BSFC may be closer to .75. And if you had a 600 h.p. engine, your gph requirement would be 75.
Sure the advertised rating is free flow. Any length of line or rise can slow the flow, don't know I would say considerably as a blanket statement though, that depends.
Also don't forget fittings with a diameter restriction can up the output pressure (different from gph), kind of like putting a nozzle on a garden hose.

 

Most people put too large a pump on, and that's not all bad if your pump has a return line so the excess fuel can bleed back to the tank from the regulator. But if you don't use all those gph the pump will be working hard against head pressure and might cause early pump failure.
It's actually pretty hard to find any hi performance pumps down below 100gph.

 

Thanks for all the replies, looks like I will be going with the Holley 110GPH mech. pump
part # 12-327-11

 

Why not the 80 GPH? It was just explained your not gonna need much more than 60.

 

Oops! My mistake, I will be going with Holley SBC 80 GPH PART #: 12-834
Instead. Not sure what I was thinking. To many things on the going with getting all the parts gathered up so I can start working on my Camaro.

 

Its real easy to get caught up in the bigger is better method of engine performance. Use restraint and some common sense and you can make a small motor out run an over cammed monster on the street.