Fuel flow/Pressure for Carb 502s

[Sport 280]

I am replacing my Mark IV hp400s with 550 horse Gen VI 502s. What fuel flow rate and pressure should an electric fuel pump have for these engines running holley carb and dart intake on Dart pro I heads?

Thanks for the help.

Fred

[ezstriper]

I would run the H/P holley w/regulator, works for me...

[mrfixxall]

Originally Posted by Sport 280

I am replacing my Mark IV hp400s with 550 horse Gen VI 502s. What fuel flow rate and pressure should an electric fuel pump have for these engines running holley carb and dart intake on Dart pro I heads?

Thanks for the help.

Fred

I like to see 6/7 psi on the throttle..

[LAKE EFFECT]

Originally Posted by Sport 280

I am replacing my Mark IV hp400s with 550 horse Gen VI 502s. What fuel flow rate and pressure should an electric fuel pump have for these engines running holley carb and dart intake on Dart pro I heads?

Thanks for the help.

Fred

Without getting to complicating the formula your looking for is for Brake Specific Fuel Consumption(BSFC), the lower the number the more efficent an engine. When you build a fuel system for a N/A motor .55 is a good number, a blower motor go up to .65. A properly tuned N/A engine will probabally come in @ .45 to .5 on a dyno.

BSFC x HP= LB of fuel and HR. .55 x 550hp= 302.5 lbs of gas an hr. Gas weighs around 6.5lbs a gallon. 302.5/6.5=46.5 gallons an hr. So any electric pump rated for more then 50gph will work.

A Holley blue pump will probabally work fine, but not get cooled by airflow like it would on a car. Aeromotives A1000 pump is rated the same as a blue pump, but cooled by the fuel flowing thru it. It also costs twice as much. 6 to 8 psi at the carb is fine.

Very important as well. An electric pump doesnt flow well or make proper pressure if it has a check ball/ check valve in front of it. So if your boat has one, remove it. It will be located at or near the fuel tanks pick up. Also mount it as low as possible in the bilge.


LE

[Sport 280]

Thanks LE, I had played with the same formula and came up with 45 gallons per hour, but was not sure I knew what I was doing!

Fred

[UrbanDisturbance]

I have twin 502's with 250 B&M Blowers. When I was at 4lbs and cruising at 3500rpm, I was running out of fuel in my carbs within 20 seconds. I could feel the boat loose power. I increased it to 6-7 lbs and I don't have the problem anymore. I have a single 850 carb on each motor. Hope that helps.

[Rookie]

Originally Posted by Sport 280

Thanks LE, I had played with the same formula and came up with 45 gallons per hour, but was not sure I knew what I was doing!

Fred

Remember that pressure and flow are inversely proportioned, and pumps are rated at a free flow state. A pump that is rated to flow 110GPH @ free flow might only flow 60GPH @ 6psi.

Might want to look at the graphs

http://www.malloryperformance.com/pd...essureCarb.pdf

[bcfountain]

i think anything above 9psi you run the chance of fuel seeping pass the needle and seat valve on a holly carb.