[REM37411]

I have a 73 Nova SS SB 350 Edlebrock performer intake and Holley 750 vacuum secondary. My question is about fuel pressure and GPH. What should I be running for pressure and is there any pro/con versus electric or mechanical pump? I do not have any current issues and the car runs great just curious.

Thanks for any tips or suggestions and if you need more information please let me know!

Thanks! Ron

 

[richard stewart 3rd]

Hi,
6to7# of pressure, fuel pumps for carbs are I think just a personal choice.
Rich

 

[GREENBIRD56]

Fuel Supply

If you take an engine to have it dyno'd - the output sheet will have a notation of BSFC - "brake specific fuel consumption". This number is usually in pounds per horsepower hour - not exactly the way fuel pumps are often rated. With a little math this can be converted to GPH (gallons per hour) - which is often reported on mechanical fuel pump spec's - but.......you need to see the output curve of the pump to know if it delivers that volume at the engine speed where you need it. Making sense? Holley publishes some of this data for the fuel pumps in its catalog - mechanical pumps. The 80 GPH pump just barely makes enough volume at higher speeds to keep up with a 300 horse engine.

My buddies' heated up T-bird Y-block makes about 300 Hp on the dyno at 5000 revs - and it uses about 30 GPH of fuel when its up there. The electric pump in the engine room kept up with that no worries (sized for big-blocks with multi-carbs etc.). Unfortunately - the little Ford mechanical pump that came with his bird doesn't have a prayer of keeping up out on the street - so ....a bigger pump that can make 30 GPH at 5000 rev's had to be fitted. With a 3/8 suction line to the tank.....

Another issue - when the horses really get up there - and this second guy's car I worked on is a 427 big block Camaro with a big electric pump .......is not having big enough needle and seat assemblies to handle the instantaneous demand. You could flash the throttle up - and suck down the float level in the 850 Holley because the necessary fuel was available - just couldn't get it in the carb. Laid down at the top of every gear. Put in a (much) bigger steel needle and seat - the flat spot went away.