1969 Dodge Dart Custom Sedan Slant Six, Father-Son Project

This is a revised repost of a thread I started in the Fuel and Air Systems sub-forum, but for the sake of this project page's completeness, I'm including some of it here
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Retrofitting EFI into a slant6-powered '69 Dart has been mostly fun, but also a little frustrating. Frustrating due to some unintended consequences, but I hope that others can use this information to learn from and maybe apply to their own projects.

The biggest change (other than the 2" hole you gotta drill in the firewall to route the new wiring harness through) is the fuel system, and my son and I knew that before making the decision:
- You need a bigger feed line diameter, a 3/8".
- And you need to add a new fuel return line.

The fuel no longer will just dead-head at a carburetor inlet; now it is pressure-regulated to stay at 22psi (for the Holley Avenger kit, at least). Excess fuel not needed to maintain 22psi is sent back to the fuel tank.

The car came with a 5/16" diameter fuel feed line. Which is great, since you can re-use that as the return line.

The rub is: the fuel tank sending unit. If you want to re-use it, you technically could for a slant-six powered Mopar. Just put an 5/16-to-3/8 adaptor just outside of the tank to neck upsize the original line before the fuel filter. The fuel flow rates for a slant six are low enough to be fed by a 5/16 line, so long as the entire run isn't 5/16. Then, add a new return line that terminates at, say, the fuel tank fill tube (there are aftermarket fittings to help do just that).


But that's not what we did. We bought the only off-the-shelf sending unit I could find that has both a 3/8 feed and 5/16 return line built-in to the bulkhead. Which I thought was great. But the Ohm range is advertised as being different than stock, which I didn't know enough at the time to pay attention to and compare against.


Bottom line: The fuel gauge is now going to be WAY off. When the gauge first reads empty, there's still going to be about 7 gallons present.

Luckily, forum member 68gtxman pointed this out to me:
http://www.technoversions.com/MeterMatchHome.html

It will match the sender to the gauge. Problem solved.O:)

The plot I made below shows how 'off' the new sender is compared with the stock one, for reference.