Just finished putting a 3.8 out of a 99 mustang into my 97 f-150 that had a 4.2 automatic trans with 245,000 miles and wanted to tell everybody how easy this swap is. There was only 5 parts I had to swap off the old 4.2 to the 3.8 and that was the intake manifold, water pump,cam position sensor,oil pressure sensor and the knock sensor. All my accessories,power steering pump,air conditioner compressor,and alternator all bolted right up.

I purchased my motor out of a 99 mustang with 3.8 automatic trans and 49,000 miles for $400.00 at a local wrecking yard. Be sure you get the flywheel with the engine because it is differant than the 4.2 flywheel and must be used, it will bolt right up to your convertor and trans. The harmonic balancer on the 3.8 is 1/2 inch bigger than the old 4.2 but was not a problem I still used the old 4.2 belt with no problems. The water pumps are the same except the fan bolted on a little differant than the old one.

Also no need to pull the air conditioner condensor,just pull the radiator and you will have room to make the swap. I placed a piece of 1/4 inch plywood in front of the air condensor in case I accidently hit it. Have put a couple hundred miles since swap and everything is going great!

 

Plenty of otherwise good F150s go to scrap because of dead 4.2s.

What did you run into with the engine wiring harness? Do the injector connections match?

 

I am sure you could just use your 4.2 injectors with no problems however mine were junk so I used the ones that came with the 3.8. Yes I had to swap the connectors (cut and splice)to the ones that were on the 3.8

 

Thanks!
I try to keep track of which injectors come with which engine. Wiring is no sweat, but if I need a single injector I can hunt one easier.

 

hi i have a motor from a 1994 mustang will this replace the 4.2 in my 1997?

 

"hi i have a motor from a 1994 mustang will this replace the 4.2 in my 1997?"

Here's how to tell:
Remove dead 1997 engine without damaging any sensors. Set it next to your 'Stang engine, then play sensor, bracket, and manifold matchup. Be careful removing injectors etc. Your 'Stang block may or may not be drilled for all the sensors so inspect carefully.
Digital cameras help a lot. I take pics of everything especially harness routing.

 

OK will the intake swap over? so the bell housing will bolt up? then i just need to get a flexplate for an auto for the 3.8l as this mustang is a standard and the truck is auto. do these 4.2L units have a knock sensor in the block? will the front acc brackets from the 4.2 work on the 3.8?
thanks again

 

"hi i have a motor from a 1994 mustang will this replace the 4.2 in my 1997?"

Here's how to tell:
Remove (assuming it's dead) 1997 engine without damaging any sensors. Set it next to your 'Stang engine, then do sensor, bracket, and manifold comparison.

Be careful removing injectors (pull out as straight as possible to avoid knocking off the plastic caps on the tips) etc. Your 'Stang block may or may not be drilled for all the sensors so inspect carefully.
Digital cameras help a lot. I take pics of everything especially harness routing.

 

Where did you find an engine and transmission that cheap. I live in Alabama and the cheapest 4.2 is 1400.00. Now when you look for a 3.8 that cuts the price in half to about 750.00, and that is without the trans. I would be willing to travel to get the price you got. Were are you located?

 

I found a 2001 3.8 w/ 121k miles for $500 going to r&r my dead 99 4.2 we'll see what happens I may sell the 4.2 crank to someone who wants to stroke
there 3.8 mustang idk yet LOL

 

You have to be careful of the years but low end used car dealers have been putting Mustang 3.8's into 4.2 F150's for years. For best results do two things, strip the engine naked. Keep only the basic block and heads, change EVERYTHING else. Change it all, it's just nuts and bolts and a few fresh gaskets. Except the flywheel, you need to use the Mustang flywheel or flexplate in the truck.
You want to be sure which engines exactly will work in your truck before you buy one, get too far off in years and they won't. As far as I know you can't use a 3.9. A good junkyard guy who knows a bit more than just what the parts counter computer strictly says can tell you more.

 

t.y. for the info I got A 2002 3.8 so as not to get too far ahead in years it only had 120 k miles on it. I know i'll have to swap the upper intake and all the front
accessories. I'm ase certified w/50 years turning wrenches but mainly GTO's lol I'm pretty sure I can get there. I got the truck for $500. + $500 in the engine
I estimate about $1300. when done & have a decent truck

 

THESE ENGINES ARE FAMOUS FOR THE LOWER INTAKE LEAKING COOLANT CREATING A MISS AND WATER IN THE CYLINDERS. FORD FINALLY CAME UP WITH A IMPROVED GASKIT IN 03 THE TRUCK I BOUGHT HAD THIS ISSUE = 4.2 LOCKED UP = WHY I PUT A 03 3.8 MUSTANG ENGINE IN IT. IT RUNS GREAT NOW. FRONT ACCESSORIES SWAPPED OVER EASY HAD TO USE 4.2 FUEL RAILS & UPPER INTAKE + CAMSHAFT SYNCRONIZER . MINE IS A 5SP SO I HAD TO USE A 3.8 STANDARD FLYWHEEL AS WELL . SORRY THE THE CAPS I WEAR BIFOCALS SO IT'S EASIER FOR ME TO TYPE. I ALSO CHOSE TO USE A ELECTRIC FAN & ELEMINATED THE CLUTCH FAN YOU CAN OPT TO USE A 4.2 WATER PUMP AND RETAIN THE CLUTCH FAN SET UP