Converting back to carbs

Todd Simpson · 10-02-2011, 05:22 PM

I am replacing the 3.2 in my '71T with a Weber carbed 2.7. My '71 already has the send and return fuel lines in the tub.

How should I plumb the "new" engine? I know I'll need a fuel pressure regulator.

Can I use my existing Carrera 3.2 fuel pump? It'c currently wired to the DME, should I just wire the fuel pump to ignition on?

Thanks

Todd Simpson · 10-03-2011, 05:20 PM

bump...c'mon carb guys...what is your setup?

kerthunk · 10-03-2011, 05:40 PM

You can use the 3.2 fuel pump as long as you have a pressure regulator on it...unless you want to see a Weber fountain.

You can pull the DME and chuck it since it won't be used anymore. I'm not sure what kind of electrical changes were made to the car to install the 3.2, but you will most likely need to undo all of that. You will need to grab a decent wiring diagram and track all of the wires to bring it back to stock. The engine harness will be different, so you need to verify all of the connections on the 14-pin connector. Could be a lot of work depending on the quality of the 3.2 install job (correct colored wires, etc).

daniel911T · daniel911T's Garage

Pelican offers the PMO fuel pressure unit. It works great, and will work even with a CIS pump as long as your return line is pretty free of restriction.

Pelican Parts - Product Information: PEL-PMO-PCU

As for wiring... it will be much simpler. Take a look at the diagram for a '69 onward. The only wires I have going to my motor are the bundle to the alternator, and wiring for the coil and MSD. Super simple. On a '69 there is a relay for the fuel pump in the engine bay, but if you're starting essentially from scratch, then rigging a fuel pump relay up front by your fuse box should be no trouble at all and would be a better choice.

Whatever you do, you'll lose about 10lb in wires and other crap.

For your sanity, pull out every unused wire, connector, computer, sensor, etc. If you leave that stuff you'll drive yourself mad troubleshooting in the future. The '71T engine bay had very little wire in it, and should only have one extra wire once you've hooked up the necessary stuff for your engine. (The extra wire goes to the overrun system on the Zenith carbs.) Get a large format wiring diagram for your car and visciously, with great malice, remove everything that isn't on the diagram. It'll make your life SO easy in the future.

Good luck!

-Dan