Hello I have a 1993 f150 xlt that has a 351 in it that gets horrible gas milage so i was thinking on putting in a brand new 302 with a few changes to cam and pistons ect. the 302 is out of a 1994 f150. I have the computer from the 1994 and want to know if i can just change out the 351 computer with the 302 when i cange the motors or will it cause other issues. I have never done a motor change in newer vehicles so any help would be great. Also should a 351 get about 8 miles to the gallon on the highway? The thing runs super without a miss but drinks gas. The 302 motor in my 1994 gets 20 miles to the gallon.

Thanks

 

You should be getting a lot more than 8 mpg. That's 460 territory. I would dig into that before you put another motor in it.

 

Well the local ford dealer can't give me any reason for its bad gas mileage either. I have had everything replaced from fuel filters to pumps tps sensor idle moter all tuned up and timed the motor has 145k on it. there is no codes in the computer like I said it runs great so just gonna scrap it and put in a better motor. I have always had great luck with the 302 never been a big fan of the 351 seems underpowered.

 

Somethings not right with that 351w. The 351w will get the same gas mileage as the 302 bacause its in suck a big truck. And the 351w will have more torque and power and is not having to work as hard.

And there is not way you're getting 20 mpg with a 302 in a 1/2 ton pickup running 10% ethanol gas. I get 15-16 with my old 302. 18 before the ethanol crap.

Is the 1994 302 computer Mass air or MAP?

 

Sounds like the local ford dealer doesn't know what they're doing. But how much have they taken off you trying to fix this? Your money would have been better spent at a competent mechanic.

Also the 351 has more power than the 302... by a mile.

 

Most dealerships nowadays don't have real mechanics. If it doesn't hook up to a computer, they're lost. There's only so many things that kill your mileage like that. Troubleshooting them one at a time isn't too hard, just takes time. The 351w is a much better truck motor then the 302.

 

X2. Hopped in a bronco with a 351 on time after getting out of one with a 302. Give it the gas like a 302 and liked to broke my neck, lots o power.

 

My bet would be on the O2 sensor.

 

Lack of power? Poor mileage? Sounds like timing to me. Possibly a jumped chain.

 

You have the better motor already.. there's just something wrong with the truck. I've had both engines in the same truck and the 5.8 got better milage overall and produced tons more grunt.

Besides the engine is the truck stock? If not exactly what has been changed?
Is fuel pressure normal? (40psi with vacuum removed from the regulator)
Does it have dual tanks and if so does it get the same milage on both tanks?

 

Well thanks for the replys guys. I do get 20 miles to the gallon in my 94 it has a mas air flow sensor the 93 does not. I have put in a new O2 sensor as well. the truck is stock other than a 3 '' magnaflow system. and my 94 with the 302 walks away from the 93 like nothing and the 94 has more miles. I really am at a loss on all of it. I did check timing and it is dead on well atleast the mark have not checked the chain. I get about 100 to 120 miles on a completely full tank on my 93 and i get 300 miles on my 94. my 94 does not have big tires and I use cruise on the hwy. anyone know about the computer swap?

 

I'm not saying that I doubt your mileage claim, but I have never heard of a 302 powered F-series consistently getting that kind of mileage, ever. Mass air or not. Most get 15 or 16 MPG with an occasional 18 MPG figure thrown in if that tank had a lot of highway miles.

The 3" exhaust is probably doing more harm than good. Too big of an exhaust pipe and you will actually lose torque. I am sure that there is something wrong with your truck and a 302 swap is not going to be the answer. If you don't figure out what's wrong with the motor, then you might go through the trouble of the swap, only to find out that you now have a truck with a smaller, less powerful engine that gets really bad mileage. I would hate to have that as the outcome.

You can swap computers, but control of the electronic transmission is also handled by the computer, so if you have a 351/E4OD transmission and are going to a 302, you need a 302/E4OD computer. You can use the 302 computer if you also swap over the transmission though. Some combinations are not available or are hard to find so the easiest thing to do might be to swap the whole drivetrain over. I hope both are 4 wheel drive.

 

Well thanks for the info Andym. On another note yes it does have 2 tanks and still gets same mileage on both tanks. and they are not 4 wheel drive no. I have also put on a new fuel pressure regulator wich made it start alot better but did nothing for mileage. could a bad transmission cause bad mileage? It seems just fine shifts very smooth and no clunks or anything but about the only thing I have not changed lol. both are automatics with push button O/D

 

Does your spedo work at all speeds/are you using the odo for mileage?
-Mike

 

yes the spedo works fine I have checked it alot with the radar things around town and it is dead on with them.