CAV GT40 going to injection on a 302 with FAST 304152 and TEC 3 Electromotive

So, I have had my GT40 for a few years. When it was built it was going to get injection and at the last minute the owner decided to just use the ignition side of the Tec 3 and slap a Holly carb on it. It has never run right. So, I just picked up a FAST 304152 and I am going to start working on it next week. It has a TPS, IAC, 4 injectors, etc. The computer is in the car, working on the ignition side etc. I need to come up with some sort of fuel switching setup to return the fuel to the correct tank. Also...I need to come up with a place to return the fuel to. I am thinking the fuel neck. Has anybody done this? Should I get rid of the low pressure pumps all together? The motor is around 350hp. Nothing crazy. Crate 302 motor.

Thanks,

Sean
 

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Ian Anderson

Lifetime Supporter
Supporter
Hi Sean
You are about to enter the world of lots of plumbing and electrics.

You do not mention what make of car you have and each has its own problem areas.

How it is normally done
Basically you make two systems , a low pressure one and a high pressure one

Low pressure goes tank through low pressure pump filters to swirl tank and return to the same tank .... more about this later

And then a second system from swirl tank to high pressure pump to pressure regulator to fuel rail and return to swirl tank

The problem with a GT40 is the tanks are long and narrow and with a rear outlet on the tank from about half tank or less under braking the fuel sloshes forward and leaves the outlet to suck air, so getting rid of the low pressure and swirl tank is not really an option.

Easiest method is to use a Pollack valve with six connectors and basically when you select which tank you use it changes both the flow and return side of the system. They work ok but are plastic body and also do break down so basically will need replaced over the life of the car, (I am on my second and it is now going iffy)

You then need to decide if you want to use two or three fuel pumps (one or two low pressure pumps and one high pressure)

Two low pressure one on each side feeds to the pollack valve and then swirl etc pollack valve on the pressure side of the pump
One low pressure pipe fuel tank toPollack valve and then to pump so Pollack valve on suck side of pump.
Both systems work.

And then swirl tank to a good quality in line pump to filter to fuel rail pressure regulator and return

Of course you can also plumb things in using non return valves, and solenoids and the complexity increases.

Returning fuel to tank
I would suggest returning near the tank outlet. Near the filler and on low tanks the circulating fuel has a lon way to travel to get back to the outlet
One position I have seen for the return is into the top of the fuel level indicator unit, normally held in with six bolts, take it out, drill a hole for a return connector and have it braided into place.

Ask away for anything that is unclear

Ian
 

Chris Kouba

Supporter
My system is similar but different, with two low pressure pumps and no selector valve.

Both low pressure pumps feed the swirl pot, but the return path of least resistance is to the driver's side tank (as Ian recommends, right next to the pickup). I typically run the driver's side pump which runs down the driver's side tank, and when it gets "too" low, I run the pass which continues to supply the swirl pot, but also replenishes the driver's side tank. This saved the valve and connections, etc... Just need to be careful not to continually run the pass side if the driver side isn't empty.

As stated, both these fill the swirl pot. A high pressure pump draws from the swirl pot (~4 gal, so very little opportunity to induct air into the system unless you're REALLY low on gas), and this circulates to the fuel rails and pressure regulator on the motor, returning surplus fuel to the swirl pot- which also allows it to cool a bit.

Sounds like our builds are similar, I have the M-6007-X302B from FMS which is also a 302 with a mild cam, 345hp/345tq. Matched with a ZF box, it's a great combination. With the fuel injection (mine is Edelbrock Pro-Flo), it runs fantastically**! You'll love it.

Chris


** - While cruising home one night last month after dinner with a friend, my EFI ECU died on me with virtually no warning. Right up until then, it had been flawless. Despite Edelbrock no longer supporting the version I have, I have found a new ECU on the second hand market and am trying that. If that doesn't work, I will upgrade to a newer system. The performance and driveability of the motor is truly fantastic. It is so worth it. PM me your number if you're in the states and I'd be happy to chat about it with you.
 
Thanks for the great responses guys. After lots of research and talks with our own local V8 tunners here in San Diego I made a decision. I purchased the FAST 304153. It has four 80lb injectors, a TPS, Idle air valve, fuel rail, temp sensor. It's amazing. Now...I just have to install the thing. I will keep everybody updated. I had a lot of positive feedback about it. I talked with a few guys that race with them and just love it. Also talked with some street guys that said it's perfect for daily driving and easy to tune. So...we will see. Next stop for me is designing the return system for the fuel pressure regulator. I like your ideas Chris, Ian and Dave. Thanks for the response!
 
I installed fitech fuel injection last year. It runs great. I kept the 2 low pressure pumps circicuits for quick fall back to carb if needed.
The output of the low pressure go into an edelbrock intermediate tank where the high pressure pump is imerged.
No more fuel starvation when tank is half full and or braking hard.
Fuel return is on one tank only.
 
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