300ci 94 300 EFI ?s

This applies to 300ci engines only
InlineDave87

InlineDave87

Famous Member
Here soon im gonna be working on a build for my work truck. But I need some info before finalizing my plans. Currently I am leaning toward MPGs but i would like to add some power/make more efficient too.
Specs is inline 300 with M5ODR2 stock for now.
If i change rear diff on my truck would the computer need to be recalibrated? Or does each diff have its own tone ring that will correct the computer?
I have an aussie speed intake with bosses for port injection, its a 2 barrel design and i got a pretty good idea on how to modify it to still use the stock throttle body or a 351 throttle body incase i really wanna turn up the power. Would the aussie carb intake be ok or would it be better to stick with the stock intake?
Ill start with these questions for now as i need to get some sleep before taking my daughter and myself to school tomorrow.
 
Stay with the stock EFI intake manifold for now.
Are you keeping the stock EFI system?
 
Yes, i was going to get a different QH that i was told about so that i can change injectors and tune it for the power level. Im thinking the mods im gonna make are gonna bring it just south of 200 hp. I havent done the math yet but i think that will require the 19 lb injectors. But depending on how finances go, i may have to use what i already got and just swap it to carb and tune it from there. Im thinking of keeping this truck more stock cause my wife gave me the green light to continue to build the truck in my garage, the short bed single cab in place of a mustang. My biggest thing was swaping diffs so my short bed will have the 3.55 and my work truck will have the 3.08 for economy.
 
InlineDave87 said:
Yes, i was going to get a different QH that i was told about so that i can change injectors and tune it for the power level. Im thinking the mods im gonna make are gonna bring it just south of 200 hp. I havent done the math yet but i think that will require the 19 lb injectors. But depending on how finances go, i may have to use what i already got and just swap it to carb and tune it from there. Im thinking of keeping this truck more stock cause my wife gave me the green light to continue to build the truck in my garage, the short bed single cab in place of a mustang. My biggest thing was swaping diffs so my short bed will have the 3.55 and my work truck will have the 3.08 for economy.
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Feeling like a broken record repeating what carb-conversion guys don't want to hear: you will NEVER come close to the economy you have now with a carb. Power loss is more likely than power gain.
The carb may come close if- and IMO- only if you keep the computer controlled ignition system intact. Dave there is NO fixed ignition distributor that will time correctly for all conditions on an EFI head. Just got reminded of that again today- pulled a loaded trailer in 100* heat. Once the engine passed 190*, started rattling. At 200 the pinging was constant. At thermostat temp, runs perfect. Curved DS2 distributor. Without changing to a carb head, the factory EFI is not going to be improved upon by deleting the ECM and using aftermarket parts, when looking for economy and normal driving conditions.
 
Yea, thats what im seeing too. And im down south were its 100 degrees like 90% of the year, or higher. My main question i was trying to get answered is if my computer will need to be recalibrated if i changed my rear diff from the current 3.55 to 3.08 from my other truck. Im sure its mainly gonna affect the speedometer but i guess i can always install a GPS unit to get accurate MPH.
 
You should not have to recalibrate the computer if the rear diff is changed. Ford trucks of that year don't care what ratio is in the back. Your truck may have a speed sensor attached to the transmission, but it's just looking for a signal. You can just change the speedometer gear in the transmission to the one for the 3.55 ratio.
 
InlineDave87 said:
Yea, thats what im seeing too. And im down south were its 100 degrees like 90% of the year, or higher. My main question i was trying to get answered is if my computer will need to be recalibrated if i changed my rear diff from the current 3.55 to 3.08
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No.
 
I have a '94 F150 with the M5ODR2 tranny and the speedo runs off of the sensor in the diff. There is no speedo drive or speed sensor in the tranny. Yhe speedometer is programable however, so you can correct it for any gear or tire change by inputing a new calibration number. I'd have to dig around a bit to find the proceedure and formula.

As for intake manifolds, I will be using an Aussie that I have modified to take injectors. The Aussie should allow more air flow at higher RPM, whereas the stock intake with its longer runners would be better at lower RPM. So if you're going with a higher (lower numerically) rear gear, the stock intake should be better. I am going with a mild turbo setup, so having boost covers other shortcomings to air flow. I'm going with larger injectors (Ford Lightening) and a Microsquirt ECM so that I can tune it. As for Quarter Horse, it sounds like Moates has shut down, so will support in future be a problem.
 
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