Hay everyone I have a 78*corvette*this was my dad's that has past this year my promise was make it faster and better rot rod. I have a after market fuel pump that has 2 lines the stock pump has 3 lines I no what the third lines does what's is 4 I want to no what to with it . This motor is not stock 40 over on pistons aluminum heads air gap*intake 650*on the carb. School me please

 

The 3rd line is a return to tank, it eliminates vapor lock issues. It's best to use that type pump if you can, the stock pump will support quite a bit of horsepower. However if you have to use the 2 line pump then plug the small return line that leads back to the tank.

 

Welcome aboard. Sorry for your loss and that's quite a fitting way to remember your dad. And don't hesitate to ask if you need help. Also, post your town in case there are some old farts here, like me, that live near you and would be glad to lend a hand.

 

Hay everyone I have a 78*corvette*this was my dad's that has past this year my promise was make it faster and better rot rod. I have a after market fuel pump that has 2 lines the stock pump has 3 lines I no what the third lines does what's is 4 I want to no what to with it . This motor is not stock 40 over on pistons aluminum heads air gap*intake 650*on the carb.

Hey everyone! I have a 78 Corvette that use to be my dad's. He passed away this year. My promise to him was to make it faster and a better hot rod.
I have an after market fuel pump that has two lines, while the stock pump has three lines. I know what the third line does (what's is 4 I want to no what to with it .)(This last part of the sentence has me stumped.) The motor is not stock, the pistons are .040 over, aluminum heads, air gap intake manifold and a 650cfm carb.

 

Here is the correct fuel pump for the car. I would not use a Two line pump on this car for the obvious reasons others have said Vapor Lock. You want it go back in the way it came out. The Mechanical Pumps will work with High Performance engines unless you have a really large carburetor over 750 CFM. Mostly a 350 engine will not really ever suck in fuel/Air mixture over 550 CFM unless it is highly modified. The Stock Rochester Q-Jet generally does not suck more than fuel/Air mixture 400 CFM with the Secondaries open since it uses Vacuum to open the Secondary and after market carburetors with vacuum secondaries pretty much do the same they will only open as far as the vacuum opens them up and only suck in the CFM which is Cubic Feet per Minute of Air they can ingest. I always felt this was an awesome designed carburetor since it will only suck in the Air/Fuel Mixture the engine can ingest and will not waste much fuel.

Since you did not tell us the type of carburetor I will use this statement. Now if it has mechanical secondaries that is whole new story since they dump fuel whether the engine can burn it or not. Then the engine has to breath through the heads and exhaust to burn all the fuel dumped into the engine. Mechanical Secondaries just open and dump fuel which wastes fuel but at the same time can provide more performance but your wasting fuel that the engine does not fully combustion in the heads.


here is a CFM Calculator

http://www.summitracing.com/expertad...cfm-calculator


http://willcoxcorvette.com/product_i...roducts_id=535

Since you have asked to be educated I figure I will share more information.

If you are choosing to install an Electric Fuel Pump with 2 lines than you may need to install a regulator for the return lines to the tank. This is to keep the float in the Carburetor from being over pressurized and return the excess fuel to the tank to also like others said avoid Vapor Lock.

Since you are younger and may not know what Vapor Lock is then here is an article I plagiarized and will happen without a fuel return line to the fuel tank.

I have known dudes that installed an Electric Fuel Pump of 7 PSI on older engines without installing a regulator to return the fuel to the tank and when Summer hits their engines will Vapor Lock on long trips. They sit on the side of the road until the fuel lines cool down then can travel again.

The reasons for vapor lock
Fuel will turn to vapor in conditions of high heat and low pressure. If the fuel line to the engine becomes hot, the fuel inside the line becomes hot. Liquid fuel turns into vapor or gas. The fuel pump is not able to move the vaporized fuel and the engine will stall. As long as the vapor remains, it locks out the fuel flow. This is why your engine will not restart until it has cooled down. The problem occurs more often in carburetor engines, especially those with mechanical fuel pumps. These systems create a vacuum that pulls fuel. If the fuel vaporizes, the vacuum will not work.

 

thanks for the info. But like i said I no what it is and what's it's for I am asking can I run the two line pump? It is mechanical just like what is on there. I guess I am asking can I run that two in line pump with out any issues and what do I do with the line going back to the tank? And I live in Atlanta Indiana thanks for everyone help

 

oh yes it is a elderbrock 650

 

I am would like to know if I can run the to line pump it is a bit better than the stock pump it is running into a elderbrock 650 carb and if I can run this pump what do I do with I line running back to the tank?

 

thanks I live in Atlanta Indiana

 

You can run a 2 line pump. I have a 78 and been running this Holley http://www.summitracing.com/parts/hly-12-327-11 for the past 13 years without a problem.

Why do you feel a need to change the pump though?

 

I done a lot of work to the motor new aluminum heads air gap intake. And 650 elderbrock carb the pump is a little bit better than stock want to make shure I get enough fuel

 

They're rare. Welcome.

 

Actually, no. This carb is is 100CFM smaller than the stock Qjet and is a very antiquated design.

A 2 port fuel pump is a downgrade from the stock 3 port.

 

I have to agree with Mike on this one since I provided a butt load of information on why you should not run a 2 line pump. VAPOR LOCK in the heat of the summer is the main reason. The only fuel that gets pumped back to the tank is what is not being used on a 3 line pump.

You would be better off with an Electric Pump with 7 PSI for Steady Fuel and a Regulator to feed what is not being used back to the tank. I know I am old and not very smart since I have never done it before on Say a 1971 Ford F100 with a 390 Engine out of a 1967 Fairlane GT500 that would only get like 6 MPG since I could never keep my foot out this type of power while using a Carter AFB 750 CFM Vacuum Secondary Carb on the engine with an electric fuel pump and regulator to the return over pressurized fuel back to the tank. I could smoke the tires at 20 MPH if I dropped the petal to the floor but again not really all that smart then working on engines and cars since i know people know more than I do

Maybe I wasted my time on this one but I have read a few performance engine books and how to build performance engines out of small block 350.

 

ok you have convinced me I will use the three line pump .and will send the 2 line line pump back. Thanks to everyone's help. But I got another issue my stock hood will not fit now with what I have done. I'm 1 inch higher than before. I have been looking at elckers hood on line . I like the stinger look will it fit? I don't want a 4 inch rise. I am afraid it will cut vision over the hood. What do you recommend

 

Get rid of the air gap intake and get something that fits.

 

I only have to choices for a intake. And had one on there . I want to go bigger

 

You're wasting you're money, but it's your car.

 

You need a dropped base air cleaner. Then your air gap manifold will fit under a stock 78 hood.

 

well next time I will build it the way you want. Thanks