I need to upgrade the fuel system on my AMC challenge car but don’t want to blow the budget doing so. The car was swapped to EFI from carb and is running the stock tank with an external Walbro pump. That worked ok till the pump sucked up a bunch of junk from inside the tank. Tank also doesn't’t have any baffles and will fuel cut when it gets below half way full. So I’m starting fresh and would like to build a system that will support 400hp.
Car currently has 5/16” feed and 1/4” return lines and the rail fittings are both 5/16”. Fuel pressure regulator is built into the rail, but I also have a rail from a later engine without it. The rails have push on fittings so I’m running Cherokee fuel lines which have that connector. Lines run half the length of the vehicle where they then have the factory barb to hook up to rubber hoses. They then hook up to the stock AMC lines which are getting kind of rusty. New lines would be nice but I’m probably looking at AN adapters for the stock rail then lines and fittings back to the tank. Running a later fuel rail would eliminate running a return line to the front of the vehicle but then I’d need to use a 99-04 corvette fuel pressure regulator/ filter combo. Saves money on the line and fittings but adds cost to the filter/reg.
As for parts available I have a Jeep Cherokee tank I picked up for free which has some baffles and internal pump. Filler neck will need to be relocated but other than that it will bolt into the car. Sending unit has a 3/8” feed line and 5/16” return. I could go with a cell but that’s more work and budget. Another option is clean and sump the stock tank but it still won’t have any baffles.
So I guess I’m looking for suggestions on where to spend money, what I should do about the lines, and what kind of lines I should use.
Here's an idea: Build a removable baffle chamber, attach it to the bottom of the tank with magnets, maybe tie it into fittings at the top of the tank as well.
Don't worry about the size of the lines:
http://ipgparts.com/blog/fuel-line-sizing-what-size-do-i-need/
As for pumps, can you do an in tank setup and get two pumps from junkyard Ford Tauruses or something and t them inside the tank? As long as the pumps are the same you should have good pressure and double the volume potential.
GameboyRMH said:
Here's an idea: Build a removable baffle chamber, attach it to the bottom of the tank with magnets, maybe tie it into fittings at the top of the tank as well.
A lot of fuel pump modules are just that- it's a self contained pump, swirl tank, and float level all in one thing. One may have to modify the tank to make one fit. And given what they go in, they are not that expensive, too.
I've recently redone the Dart's fuel system - I needed to replace the fuel tank, and while I had a new tank that had never been filled with gas, I decided to weld a Wal-Mart bread pan to the underside to serve as a sump. It's plumbed to an external Walbro 255.
If you run the external pump, and have a return line, connect a T fitting between the tank and the pump. Connect the return to that T fitting.
Also might be able to run a filter between the tank and pump. Ideally mount the pump as low as possible.
Do you have a TIG? If so, alloy fire extinguisher bottles can make excellent surge tanks, and as suggested above, oem pumps are winners. I would look under euro stuff like old volvos and mercs for bosch pumps, two of those using mostly stock hardware would easily meet your needs. In terms of filling a surge tank from the main tank, sump the main tank, and use a non-efi pump to transfer to the surge tank. Note, this pump should be able to pull good vacuum and move your average powerband fuel demand continuously. It does not need to meet your peak demand as the surge tank can cater to that. Return line from engine goes to surge tank and from surge tank back to main tank. I actually used an OEM-like bosch for my lift pump pulling through a big marine style filter (raycor) and it worked fine for my 400hp setup, but later swapped to a high capacity carby pump instead (carter black). Your tank-to-surge filtering could be any kind of scavenged OEM housing like a BMW oil filter housing. The transfer pump can be EFI as long as the filter is a small enough restriction.
Lots of ways to skin the cat, hopefully that gets your mind ticking over a bit more :-)
Re lines, 5/16 is fine, but beware of having excess fuel flow to the engine with a 1/4 return as this can affect regulation effectiveness. Equally, beware of your regulator being outflowed by this new dual pump setup. You could potentially mitigate that by PWMing your pumps, or running one of them up to X RPM, or similar. Many turbo jap OEMs use a resistive drop for puttering around and switch the resistor out for higher load usage, eg turbo silvia and others.
I drew this maybe 10 years ago, it's along the right lines:
