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Carb to EFI conversion questions

Carb to EFI conversion questions

  
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Carb to EFI conversion questions

 
Kirby777 Kirby777
New User | Posts: 1 | Joined: 06/12
Posted: 06/21/12
01:36 AM

Ok, so i have a 1979 Ford F250 High Boy with a 390ci ford with a two barrel carb and i wanna make it more drivable with the changes in altitude i deal with in Colorado and to get better fuel mileage. so my question is....... is their a somewhat cheap EFI conversion kit that is going to be good for what i want to do or does anyone have any suggestions?

~kirby777  

waynep71222 waynep71222
New User | Posts: 17 | Joined: 05/12
Posted: 06/21/12
11:37 AM

first... before you do anything...  you will want to stop by the local exhaust shop.. have them install an oxygen sensor bung. in the exhaust pipe just below the manifold connection..  if you don't already have one..  this way you can install a single wire 40 buck oxygen sensor and a 40 buck air fuel ratio gauge ...

if you have headers.. and need to install it farther down into the collector.. you will need to select a narrow band 3 wire sensor and use a relay to power the heater wiring on it..
this will give you the best idea of where your air fuel ratio is...

since you have a motorocraft 2150  carb that looks like this.. you have an excellent carb..



see the choke pull off.. with the spring (barely visible) on the actuator arm..   if the choke pull off is not working.. do to leaks or missing vacuum hoses..  the choke will stay closed..  ruining your fuel economy..

when was the last time you rebuilt this carb.. they do have power valves that blow out..  leaking fuel internally.. these are NOT hard carbs to rebuild with  just a kit and a few cans of spray cleaner..

getting the small passages clean will really really help....

2100Idlecircuit2

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2100Maincircuits


as for a cheep EFI conversion.. nothing is really that cheep..

i don't deal with a lot of aftermarket EFI systems.. i do recall seeing one for the 2 barrel.. but i don't recall what brand..

you do have the option of installing a TBI system from a GM car or truck..   you will probably need a TBI system off a 454... as the 350 injector flow would be just a little lean .. the police impala system might be close...  but there are 2 different flow rates for the 454/ 7.4 systems..  an adaptor plate to go from the 4 bolt motor craft mounting to the 3 bolt TBI hold down is available.  or easily fabbed...    you can even use your existing duraspark distributer with it..   you will need to convert to a 7 pin GM module.. but it will be really simple to do so..

will it get you better fuel economy??  will it improve how it drives.. probably..  

there are actually Ford CFI fuel injection throttle bodies.. but they use very high pressures and special injectors.... get a blue or grey top injector throttle body.. but then you need the higher pressure pump.. and may have integration problems with the GM computer..  the ford CFI computers are not as user friendly as the GM versions are for swapping..

personally before going to EFI..  i would climb under and check the timing chain freeplay by using a breaker bar with a tight fitting swivel and a socket with a plastic bag to take up any clearance between the head of the center crank bolt and the socket..  then rock the crank back and forth.. does it have more than 1/2 inch.. and thats a lot. .of  slack before you can feel the cam start to turn..????

have you verified the EGR valve is working properly..    and also taken it off and verified that there is ZERO leakage through the valve exhaust passage when its closed..    that would be an exhaust leak uncommanded into 16 inches of vacuum.. does not take a Lot of uncommanded leak to screw up the air fuel mixture..

don't think about disconnecting the EGR.. unless you are going to monitor and rejet the carb..

why...

there is about 21 percent oxygen in the atmosphere.. the EGR flow into the intake reduces the percentage of oxygen content in the incoming air charge so less fuel is needed for the volume of air..

egr flow is not supposed to happen at idle..  

GTluvr GTluvr
User | Posts: 80 | Joined: 06/09
Posted: 08/18/12
08:16 AM

There's a company called FAST that makes a bolt-on replacement for carbs. They are self-learning so you don't have to spend a ton of time reprograing the computer. I've only read about these in product review spec sheets, so I have no first-hand knowledge about how well they work, cost or any other bugaboos that may be involved. Holley, the reknowned carb manufacturer also makes a conversion kit. The beauty of the internet is that you can look things up BEFORE you buy them.  The problem with this website is that there's not alot of input. Scan some of the other posts and note how many hits there are versus how many responses. The ratio isn't very promising.  Try Googling the set up you are interested in and see what pops up.

GT