From EFI to Carbs

[MacDrizzle]

This may be a stupid question. When going to carbs on an OEM EFI vehicle, will removing the ECU affect the outgoing ignition circuit as well as the electric fuel pump circuit? I realize i only need power to the starter coil and dist. I'm trying to keep the harness pretty much untouched.

Pleezz help, me clear up the rats nest forming in my brain.

[DubstepDave]

Your ECU controls both the fuel and ignition systems. To convert from EFI to carbs you would need to run a dedicated programmable ignition module (I do not believe that there is a vacuum advance distributor available for KA's), and a carb specific fuel pump (or at least a fuel pressure regulator as carbs are normally meant to run at 3-9psi depending on the application and carb(s) used, and fuel injected cars usually run at 45-60psi). You would need to cap off the fuel return on your tank as well.

[MacDrizzle]

Your ECU controls both the fuel and ignition systems. To convert from EFI to carbs you would need to run a dedicated programmable ignition modoule, a carb specific fuel pump (or at least a fuel pressure regulator as carbs are normally meant to run at 3-9psi depending on the application and carb(s) used, and fuel injected cars usually run at 45-60psi). You would need to cap off the fuel return on your tank as well.

David thank you for the good info. I am running a MSD 6 series, will that work or do i need something else? I was planning on a Walbro 255 with a regulator. As for the return cap off, would i just use a rubber cap with hoseclamp?

[DubstepDave]

Walbro 255 will be too much pressure. I would look into some carb specific fuel pumps that muscle car guys run. As far as capping it off, you would need to use something that's made to resist fuel, as most rubber will deteriorate quickly and leak if it isn't meant to be used with gas.

As far as the timing is concerned, I've never messed with the MSD stuff or using dedicated ignition control stuff, so I can't really help you there. All I know is that the stock ECU controls the ignition/timing on a KA, so you would need to figure out something to replace that if you went to Carbs. You might be able to leave the ECU in place to control your ignition and then just run your carbs.

[MacDrizzle]

Walbro 255 will be too much pressure. I would look into some carb specific fuel pumps that muscle car guys run. As far as capping it off, you would need to use something that's made to resist fuel, as most rubber will deteriorate quickly and leak if it isn't meant to be used with gas.

As far as the timing is concerned, I've never messed with the MSD stuff or using dedicated ignition control stuff, so I can't really help you there. All I know is that the stock ECU controls the ignition/timing on a KA, so you would need to figure out something to replace that if you went to Carbs. You might be able to leave the ECU in place to control your ignition and then just run your carbs.

Like a Holley inline electric low press. pump? Probably something similar to what my dads running, i think holley blue. The motor im using is originally made with carbs its not gonna be the KA, so i'll have to mess with the ignition a bit to get it all to work. Ain't no thang. LOL

[DubstepDave]

That sounds like it would work just fine.

What motor are you going with now?

[MacDrizzle]

Lets just say the 240sx will have a little Z blood. Thats all i will say right now so I don't jinx it.

[DubstepDave]

So an old z 6-cylinder then, huh? You'd be better off with just about anything else, those don't make shit for power. All of the non-turbo motors were rated at 150hp or less, and it's really hard to make much more than that out of them. They are also very long motors, making physically fitting them with the radiator still in front and not having to completely re-work the firewall and move the engine/trans back 6" nearly impossible.

Just drop a SBC in it and call it good, since that's the direction you're slowly heading anyway. It would actually be cooler with a V8 than with a 240/260/280z motor anyway.

[MacDrizzle]

Oh Dave why can't you let me have my fun with anything! LOL!

[DubstepDave]

Do an LS1 swap and be done with it.

[MacDrizzle]

Do an LS1 swap and be done with it.

I have all the shit to do a big bore L24, parts are cheap. Im fabbing a 4Barrell intake for it. LS1s not so cheap, check the prices my friend. Hinson Supercars LS1 RX7 n 240SX swaps www.hinsonsupercars.com

[MacDrizzle]

I'm not doing this swap because im out to make gobs of power. I'm doing it as a fun project to brush up my skillz. I also get boners when I hear inline sixes tachin high rrrrrrrrrrrrsssssss.