26scarab

A friend of mine was dialing in a drag car the other day and had fuel delivery problems. The car is a 56 Chevy with a 468 , the car runs 10:30's. It has a Mallory 140gph in it and is running out of fuel on the big end of the track.

Now what has me worried is I have the same Mallory pump on my 540. I haven't really had any problems but since I don't have a fuel gauge on the dash I really don't know. How can a 468 use more gas in 10 seconds than my 540 at WOT for a few miles ?
What size fuel pumps do you guys run ?

mopower

#1 is fuel line size. you can have 1000 gph pump but if the line is small your screwed. #2 your gas tank is probably a foot in front of the engine not 10/12 feet behind it. Now he has to overcome the acceration , in other words the gas in the fuel line wants to stay where it used to be when your buddys doing a 10 sec. quarter. Sit next to him some time with a hot cup of coffee in your hand and let me know what happens

Understand now? Not so hard

oops , almost forgot. I have 140gph Carter mechanical pumps on my 540's with #8 hose and pressure on the dash never drops below 8 lbs.

Dave F

The way to figure it out is simple.
First, like mo said, there are alot of other factors involved with your buddy's drag car.
For you however, line size is a factor. On a single carb. use a #8 to and from that Mallory pump to 2 #6's. One for each side of the carb. Set the internal bypass and external reg for 6-8 lbs and you'll be fine.

Now, as far as the math goes it pretty simple.
take your horsepower X bsfc = lbs/hr needed / 7 = gal/hr needed.
Check that against Mallorys lbs/hr at psi chart.
The 140 will supply your 540 under the normal parameters of a n/a marine motor.

The 468 can use more fuel than your 540 if it has more hp. The problem may not be fuel consumption, it's probably delivery.

DAVE

28SS

What kind of rpm is the 468 turning?

26scarab

The 468 is turning 7400rpms.
I've thought about everthing that has been said about this but just was curious about what everyone else thinks.
I do know that the car leaves extremely hard (trans brake) and does carry the front tires quite a ways , so the g forces are a little greater than the boat.

Cord

iTrader: (2)

For a boat you can figure 1 gallon per hour per 10 horse power. ie-a 360hp engine will consume 36gph. Now a pump rated at 140gph would seem to be able to supply more than enough fuel. The getcha is that the rating may be a free flow number. In other words there is no flow loss due to pressure or friction loss due to a hose. That's why you'd need to oversize the pump. Most manufacturers have charts that will show what the real gallonage is for a known pressure. None of them will have a chart to allow for frictional losses.

Griff

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