Thread: Need Help w/fuel pump selection

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I'm installing a 383 440HP in a 79 Corvette with a turbo 350 for a friend is there an easy way to figure out which mechanical fuel pump I should use Summit offers 2 different Holley's but I don't know which to choose.Engine has no name dual plane aluminum intake,Holley carb,aluminum heads,roller rockers,high performance HEI distributor It was advertised at 440HP and dynoed at 413HP in hot air temps.Hope this helps!!!

Originally Posted by 63409ss

I'm installing a 383 440HP in a 79 Corvette with a turbo 350 for a friend is there an easy way to figure out which mechanical fuel pump I should use Summit offers 2 different Holley's but I don't know which to choose.Engine has no name dual plane aluminum intake,Holley carb,aluminum heads,roller rockers,high performance HEI distributor It was advertised at 440HP and dynoed at 413HP in hot air temps.Hope this helps!!!

Here, I'll give you an answer you can use for the rest of your life to size pumps for a given hp.
Most any internal combustion engine will use 0.5 (1/2) pound of fuel for each horsepower hour. For instance, 440 times 0.5 equals 220 pounds per hour of fuel burned. Now, since gasoline weighs about 6 lbs per gallon, we can divide 220 by 6 and find that the motor will use about 36.66 gallons per hour running at 440 horsepower.

Now, rule of thumb says to double that because the pump will have to pull fuel through small diameter tubing and against the direction of the car (under acceleration, the fuel tries to go back toward the tank, making the pumps job harder). So, if we double 36.66, we find that we will need a pump that will deliver 73.32 gallons per hour running at 440 horsepower. Now, of course, the motor will only be making that kind of horsepower for an instant at a time in a street or street/strip application, so some concession can be made if you have a pump that delivers close to that.

The more important thing to consider when choosing a fuel system is the limit of the needle and seat in the carburetor. A Holley, generally speaking, will be ok with fuel pressure up to about 6 1/2 lbs at the carburetor fuel inlet. The needle will not be able to seal up against the seat with pressure over that and will flood the intake manifold with raw fuel. This will provide you with an unbelievable tuning nightmare. Mount a 0-15 fuel pressure gauge temporarily on the cowl of the car with duct tape or tie wraps and plumb it to the fuel inlet of the carb so that you can observe fuel pressure as you drive. If need be, install a regulator and lower pressure to around 6 pounds. When you have the pressure dialed in, you can remove the gauge and be assured that your fuel system is working as designed.

Thanks this is great info!!!!! And a big help.

A slightly shorter answer My 383 RHS motor made 450 on the dyno and ran very nicely on a Holley blue top for years.

Would it hurt to buy the bigger mechanical pump in case we want to go bigger in the future [I'm an over-kill kinda guy] 1st pump specs are 80 GPH 7.5 PSI With 1/4 NPT Fittings 2nd. pump specs 110 GPH 6.5-8 PSI WITH 3/8 Fittings. I'm going to use a pressure reducer and press. gauge so I can set the press.and keep an eye on it.

Is there any harm in using the bigger of the two pumps?They are - 1st. choice 80 GPH with 7.5 PSI With 1/4" NPT Fitting 2nd. is 110 GPH with 6.5-8 PSI With 3/8 NPT Fittings I'm an over kill kinda guy so I would like to go with the bigger pump [in case of improvements in the future]I will be using a press. reg. and a fuel gauge.Will this be ok?

Originally Posted by 63409ss

Is there any harm in using the bigger of the two pumps?They are - 1st. choice 80 GPH with 7.5 PSI With 1/4" NPT Fitting 2nd. is 110 GPH with 6.5-8 PSI With 3/8 NPT Fittings I'm an over kill kinda guy so I would like to go with the bigger pump [in case of improvements in the future]I will be using a press. reg. and a fuel gauge.Will this be ok?

If I were going to do that, I would use a bypass regulator that allowed excess pressure/volume to be returned to the tank instead of dead-heading the flow, building heat in the fuel and resistance to wear out the pump.

What if I don't have a return line? [Stock 79 corvette I'm not sure, I haven't taken it apart yet] I guess I'll have to install one.Would I be better off just going with the smaller pump? Will I need a pressure reg. with the smaller pump?
Thanks for your help

OK, I'm saying you should have 6 psi at the carb inlet, 6 1/2 absolute max. You're saying that the first pump puts out 7 1/2 psi. Do you think that will work without a regulator? If so, please explain your logic.

Wow Tuff crowd. I read this to quickly I see your point I will need a reg. with either pump.I looked at Summits site and can't find any bypass regulators that will work with a mechanical pump Holley has a bypass reg. for carb. but in the notes it says not to be used with mech. pumps.Do you know where I can find one?Do you think the smaller pump will work with this engine [383 340 HP]and how far will it go [HP] before it's not going to be enough.
Thanks

Here, let's make this easy....no regulator required....6 psi max
http://www.summitracing.com/parts/EDL-1721/
And I wasn't meaning to be a jerk if I came off that way.

Not a problem, You've been a great help!!!!
Thanks again

That pump seems perfect. Thanks again!!!