Underhood fuel line routing help

[767Jockey]

Well, the problems continue, my brand new block arrived, was machined, and we found that it's no good. Right now I am "negotiating" with the supplier for a new one. Yeah, I know that I shouldn't have to "negotiate" for a damned thing on a brand new block that turns out to have porosity problems that are only evident after machining...it's a long story, I'll let everything play out before I say anything.

Anyway, the project is almost dead in the water while I wait for the block supplier to decide what he's going to do. My thoughts turn to the fuel line. I am having Nick Acton (Mickmate) build me a custom S/C style fuel tank. I'm running a Mallory 250GPH electric pump with a 1/2" fuel line. I have no mechanical pump, there will be a fuel pump block off plate there. I'll have the pump eccentric installed in case I want to go mechanical somewhere down the road. I have a large Holley !/2" in, 1/2" out regulator. I am figuring that I will put the regulator down in the area where the fuel pump normally goes. Maybe I can have a bracket fabricated for it that uses the bolts for the block off plate to mount the regulator securely, with a short length of steel braided line that bridges the hard line on the frame to the regulator to allow for engine movement. For appearance sake I'd like to run hard line from the regulator to the 1X4 fuel log. How is this line normally routed? Anyone have pictures of the stock line routing? What do you guys think of this plan - any ideas are always welcome and appreciated.
Doug

[Rick Parker]

Instead of hardline which will absorb a lot of heat I would suggest using a Black cloth covered line such as what is available from Earls. It looks good and won't transfer a lot of heat into the fuel.

Rick

[Tommy]

Regarding your plans for the fuel pressure regulator - I recommend a regulator with one input and two outputs (one to the carb and the other back to the fuel tank). They are much easier on the fuel pump. If you do that, you may want the regulator just after the pump so you don't have to run the return line so far.

[767Jockey]

Originally Posted by Tommy

Regarding your plans for the fuel pressure regulator - I recommend a regulator with one input and two outputs (one to the carb and the other back to the fuel tank). They are much easier on the fuel pump. If you do that, you may want the regulator just after the pump so you don't have to run the return line so far.

Actually the Mallory 250 GPH pump has a built in return, so I only need to run the return line from the pump back to the tank, and use a deadhead regulator.

[Cobrabill]

Originally Posted by 767Jockey

Actually the Mallory 250 GPH pump has a built in return, so I only need to run the return line from the pump back to the tank, and use a deadhead regulator.

That system passes up a great opportunity to cool the fuel,which in any equation is a great thing.

[767Jockey]

Originally Posted by Cobrabill

That system passes up a great opportunity to cool the fuel,which in any equation is a great thing.

How does a longer return line equate to cooler fuel?

[Tommy]

Sorry about my bogus advice above. I just looked at the Mallory 250GPH pump and your plan looks OK to me. The important thing is that there be a way for excess fuel from the pump to go back to the fuel tank. Some pumps simply reroute the excess fuel back to the intake side of the pump, allowing fuel to recirculate next to the heat of the pump for an extended time. Those types of pumps can lead to to vapor lock.

[Ron61]

Originally Posted by 767Jockey

How does a longer return line equate to cooler fuel?

Just the same as water going through the radiator. The longer it is going through the cooler it will be. A longer return line will have the fuel in it a little longer than a short one which will let some of the heat transfer to the line and the air will cool the line some if it is where air can get to it. That is why I didn't run my fuel lines inside the frame.

Ron

[767Jockey]

In theory I understand this. In actuality, I would be shocked to see any measurable difference in fuel temp, and even if you could measure it, the change in HP is probably zero, especially with that "cooler" fuel being dumped into a tank that holds over 40 gallons of ambient temp fuel..

[Cobrabill]

Originally Posted by 767Jockey

In theory I understand this. In actuality, I would be shocked to see any measurable difference in fuel temp, and even if you could measure it, the change in HP is probably zero, especially with that "cooler" fuel being dumped into a tank that holds over 40 gallons of ambient temp fuel..

6-7...Just so i know we're on the same page:

1)Fuel line leaves the tank and enters the pump which is mounted near the tank.
2)Return line leaves the pump and goes to the tank or the pump by itself-no return line?
3) line runs to the fuel rail and dead ends at the rear of it.

[767Jockey]

Originally Posted by Cobrabill

6-7...Just so i know we're on the same page:

1)Fuel line leaves the tank and enters the pump which is mounted near the tank.
2)Return line leaves the pump and goes to the tank or the pump by itself-no return line?
3) line runs to the fuel rail and dead ends at the rear of it.

Fuel line goes from the tank to the pump.
Pump has two outlet ports:
First is a return port that is plumbed right back to the tank
Second is a fuel supply line to the engine, goes up the frame rail of the car to a deadhead Holey fuel regulator.
All lines and ports are 1/2" in pump and in regulator.
The pump is a Mallory #5250, if you want to look it up. I'm guessing the literature from Mallory can explain it a whole lot better than I can.

[JeepSnake]

Doug,

Actually, the long return line acting like a radiator has little to do with the way the return style system works to keep the fuel cool. The circulation is what's important.

Think about a regular old carbureted fuel system: no regulators, no return. Just a fuel pump, a line, and a carb. Unless the engine is really loaded and consuming a lot of fuel, there is a bunch of fuel sitting static in the fuel line. As it sits there, the fuel line absorbs heat from the engine & headers and transfers it to the fuel. This can wind up resulting in vapor lock.

So, to solve this problem, you add a return line near the carb, and you put in a higher volume fuel pump. Now, the pump is always moving fuel through the fuel line, even when the engine isn't loaded, and returning it to the fuel tank. This cures the heating/vapor lock issue in two ways: 1) the moving fuel doesn't have as much time to pick up heat as it passes through the engine compartment fuel lines, and 2) what heat it does pick up is dispersed into the heat sink of 20+ gallons of fuel in the tank. As a friend put it to me, you keep the fuel moving and it doesn't have time to just hang out and get in trouble.

In the '70s, as engine operating temps increased, this system was incorporated into production cars to fight vapor lock. I know that Jeeps used a fuel filter just ahead of the carb with two outlets. One fed the carb, the other returned fuel to the tank so that you didn't vapor lock while creeping offroad.

Hope this helps.

[Cobrabill]

O.K.If this was my car,i plug the second port on the pump,run the line to the back of the fuel rail.Then i'd run the line out the front of the fuel rail down to the reg mounted in place of the mech. fuel pump and back to the tank.

My car is plumbed a little different.The fuel pump is out back(duh),the inlet is up front.This comes as a result of a previous plumbing arrangement(mechanical pump in the loop),then i came to my senses and trashed the mechanical.The reg is mounted at the rear of the fuel log.The return line (4AN)then is metered with a Holley carb jet and runs back to the tank.

This does two things:
1) relieves the deadhead situation on the pump.Previously discussed.
2)It does deliver cooler fuel to the carb.I know the ambient temp of the gas tank isn't exactly arctic-like but it definately is cooler than the fuel log sitting above the engine.

I know out on the Island you don't experience heat like i do,but i tend to take fuel systems one better as i have a turbo car that there is no margin for error on.

[767Jockey]

OK, fuel moving keeps it cooler instead of sitting and getting compressed against the deadhead regulator. I get it now. It takes me a while to catch on. Getting older sucks, I never thought it would happen to me.

[CHANMADD]

I run a Holley Blue electric pump.I have the pump at the back close to the tank and actually mounted the regulator on the block where the stock pump goes. It is dead headed and I have no problems with it at all. I will say that I am prbably going to go back to a mechanical pump for safety reasons and also it is not as noisy.
john

[Jerry Clayton]

Doug

the next time you are at work, you do the walk a round---notice the plumbing used---the braided stuff was WW2----toss the electric pump, and regulator, put on a holley or edelbrock mechanical pump, no regulator and hard line to the carb. Use a short rubber hose from hard line along or inside your frame to the fuel pump inlet on the engine.

the electric pumps are noisy, and create other problems and risk areas---do it like was on oem cars running carbs in the 60s and 70s---make sure your tank is vented

[CHANMADD]

I am 100% with Jerry here! I have always said that the OEM ,read ,factories pay 100's of thousands to highly qualified engineers to come up with the best and safest methods of doing things. All the other geniuses who own cars always come up with beter ways of wasting money on unnecassary and often times unsafe "bling". Just like all the threads about faulty aftermarket ignitions and the like......beats me!!!!...............KISS!!!
john

[767Jockey]

I've been told by more than a few highly respected engine guru's that other than perhaps RobbMc's mechanical pump, none of the other mechanical pumps will have the capacity to feed my engine should I decide to take it to the track, which I hope to do. I feel better with the big electric pump back there, KNOWING that it'll work, than with a marginally sized mechanical HOPING that it'll work. Every engine guy I spoke with, and every article I referenced, speced a 1/2" fuel line and a higher pump flow rate than either of the mechanical pumps mentioned in the post above. I don't have the numbers handy in front of me, that was a while ago. However, I'll stick with what I've got, I KNOW it'll work. This "genius" doesn't have all the answers, but I know enough to go to QUALIFIED experts to learn what I don't know. They said to set it up the way I have it. Last I knew, the factory didn't produce a 640+HP car, and certainly not one with a mechanical fuel pump. Required fuel flow and delivery is a function of the HP that it feeds.

[767Jockey]

Originally Posted by Jerry Clayton

Doug

the next time you are at work, you do the walk a round---notice the plumbing used---the braided stuff was WW2----toss the electric pump, and regulator, put on a holley or edelbrock mechanical pump, no regulator and hard line to the carb. Use a short rubber hose from hard line along or inside your frame to the fuel pump inlet on the engine.

the electric pumps are noisy, and create other problems and risk areas---do it like was on oem cars running carbs in the 60s and 70s---make sure your tank is vented

Jerry,
You have a PM.

[Cobrabill]

John,what safety issue?Also,how can you hear the pump with sidepipes?