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EFI to CARB


Boggin

Well-Known Member
Joined
Nov 3, 2007
Messages
5,711
Transmission
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not sure where to put this, but has anyone ever converted efi to carb? how much work is involved ? i really would like to switch and i know it wont be easy but id be willing to give it a shot if it isnt off the chart hard or very expensive and if i could get some pointers on how
thanks guys
 
Why would you want a carbed engine over EFI and what is this going to be happening to?

EFI engines give better performance, fuel economy, lower emissions, and low cost maintenance. Not to mention they are FAR easier to start up in the cold, which is good for you being a Canadian.
 
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I haven't done it on an RBV, but I have done it. In my case I was increasing the flow capabilities of the engine well beyond the usefulness of a stock and outdated open loop type EFI system. My choice was either a $2000 programmable EFI system, or $300 for a used triple Weber 2 bbl setup.

You'll need to:
replace the intake manifold
install a carburetor and air filter
adapt the throttle cable to attach to the carb instead of the EFI throttle body
run a choke cable if the carb has a manual choke
adapt (or replace) the fuel system

The fuel system is often the most difficult part. The EFI fuel system supplies fuel at a pressure much too high for a carburetor. The best way to do it is to replace the fuel tank and pump with that from a carb'ed vehicle, make the pressure line fit the pump and the carburetor on each end, and remove the return line. The vehicle I was working on had an EFI pump that was external to the tank, so I just plugged the return line and the low pressure Holley pump was a direct replacement. Most modern vehicles use in-tank pumps which complicates the situation. I have heard of fuel pressure regulators that will reduce the EFI pumps pressure to something suitable for a carb and allow you to keep your tank and fuel pump, but have no direct experience with this. It might also be possible to remove the in-tank pump from the sending unit assembly and extend the metal line down to the bottom of the tank, and then install an external pump, but I don't know that I've ever heard of this done.

After that it will run, but you'll want to tie up some loose ends. The computer can come out and the fuel injection will usually have it's own sensors that you'll want to unplug, in addition to the fuel injector harness. The harness may be bundled together with stuff that needs to stay - like sensors for your water temp and oil pressure gauges, so you'll need to run new wire to these sensors so your gauges will work.

If the EFI computer is integrated with the ignition system, that's a can of worms that I won't be able to help with. Chances are if you have a distributor, you'll be ok, but on a distributorless system, I'm not sure.
 
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I am going from an EFI 2.9 to a carb 302. I will probably just be removing most of the wiring harness down to the bare essentials, running an old points style distributor with a points eliminator kit, a mechanical fuel pump, and a fuel tank out of a carbed Bronco II.
 
A lot depends on what motor you have and what year it is. The biggest issue usually relates to ignition and unless there was a carbed version or your motor it might be impossible to find a distributor with mechanical advance.
 
I haven't done it on an RBV, but I have done it. In my case I was increasing the flow capabilities of the engine well beyond the usefulness of a stock and outdated open loop type EFI system. My choice was either a $2000 programmable EFI system, or $300 for a used triple Weber 2 bbl setup.

You'll need to:
replace the intake manifold
install a carburetor and air filter
adapt the throttle cable to attach to the carb instead of the EFI throttle body
run a choke cable if the carb has a manual choke
adapt (or replace) the fuel system

The fuel system is often the most difficult part. The EFI fuel system supplies fuel at a pressure much too high for a carburetor. The best way to do it is to replace the fuel tank and pump with that from a carb'ed vehicle, make the pressure line fit the pump and the carburetor on each end, and remove the return line. The vehicle I was working on had an EFI pump that was external to the tank, so I just plugged the return line and the low pressure Holley pump was a direct replacement. Most modern vehicles use in-tank pumps which complicates the situation. I have heard of fuel pressure regulators that will reduce the EFI pumps pressure to something suitable for a carb and allow you to keep your tank and fuel pump, but have no direct experience with this. It might also be possible to remove the in-tank pump from the sending unit assembly and extend the metal line down to the bottom of the tank, and then install an external pump, but I don't know that I've ever heard of this done.

After that it will run, but you'll want to tie up some loose ends. The computer can come out and the fuel injection will usually have it's own sensors that you'll want to unplug, in addition to the fuel injector harness. The harness may be bundled together with stuff that needs to stay - like sensors for your water temp and oil pressure gauges, so you'll need to run new wire to these sensors so your gauges will work.

If the EFI computer is integrated with the ignition system, that's a can of worms that I won't be able to help with. Chances are if you have a distributor, you'll be ok, but on a distributorless system, I'm not sure.

thanks alot man i will really look into it but first i will probably just want to get a carbd b2 for parts. hell if im gonna get a carbd b2 i may as well just use that one.. if i can find one
thanks for all the advice too ill ask my pop about it cause hes been a mechanic for his whole life
 
thanks alot man i will really look into it but first i will probably just want to get a carbd b2 for parts. hell if im gonna get a carbd b2 i may as well just use that one.. if i can find one
thanks for all the advice too ill ask my pop about it cause hes been a mechanic for his whole life

You will spend more on a custom intake and ignition for your 2.9 that it is worth. I wouldn't advocate swapping in a 2.8 in place of a otherwise healthy 2.9 either.
 
the biggest issue is that there are no provisions for dynamic spark control without a computer and for many engines there is NO points distributor made.

The ignition system can be made to work without the computer

But as I said there is no provision for controlling it, no advance/retard...

AD
 
I would do a 4.0 swap instead...easier than trying to hack together a carb for your 2.9...you are talking about your B2 right? Not the Ranger?
 
yup the b2..and i think ill leave the ol 2.9 as is for now and when she blows just get some kinda v8 carb.. maybe like a 460 hahah not.
 
Yeah, definitely way too much work for something that will give you a negative gain...

One of the local guys is building a 460 powered fullsize Bronco...should be pretty sick... he's running dual quads with some head work done and I think headers too. Pointless for any type of wheelin we do around here, but he's always at full throttle anyway so it will be interesting to watch.
 
if you have access to a lathe, you should be able
to use the 2.8 duraspark distributor. turn down
the center shaft from the 2.9 dist to match the
2.8 shaft, use the 2.9 gear and thrust washer.
check the depth of the shim in the block,
because the 2.9 pushes the shaft up, the 2.8
pulls it down.
 
i also think it would be possible to make
a carb adapter out of two stacked pieces
of 1" aluminum plate. i would make the
gaskets first and use them as patterns to
carve the aluminum with a drill press and
with a ball mill in a die grinder.
 
I thought he wanted to replace the 2.9 with a 302, not change the 2.9L to carburated.

later,
Dustin
 

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