78 King 5.0 Efi Swap Issue

Discussion in '1974 - 1978 Mustang II Talk & Tech' started by Donald Vincent, Jul 11, 2017.

  1. Hey all. New here and hoping i can find some info or help.
    I have a 78 King Cobra. The original 302 took a dump on
    me. So I figured if Im going to go threw the trouble I may as
    well make it worth my wild.I decided to go fuel injection. Well
    it is the first swap Ive ever done and Im pretty proud of myself.
    That being said, I have a small issue that I just cant seem to
    figure out.

    Here is what I have. Engine, computer, and harness are from an
    87 Lincoln mark vii LSC. It is the 5.0 HO Speed density. Its in and
    connected and seems to run great. Perfect idle in park. perfect
    idle in drive or reverse. Very smooth at hwy speed. However.

    When I take off from a stop it has no power. The orig 132hp 302
    would spin the tires at the slightest touch of the pedal. Now, it feels
    like I am hauling a 6000 lb trailer or taking off in 2nd.(Im not, I counted)
    I am still using the orig c4 and 8" rear. And I want to note that I
    DO NOT have kick down cable connected. Which is weird because
    If I accelerate I can feel it kick down. Not Like a passing gear but
    a kick down none the less.
    I guess after all that rant I am asking if the kick down must be
    connected on the c4. I just assumed Its 1st threw 3rd and without it
    I would not have passing gear.
    Thanks for any help or just listening to me rant.

    20161003_151838.jpg 20161003_151848.jpeg 20161003_151935.jpg
  2. The kickdown isn't necessary.

    @jrichker might be able to help with the EFI drivability.
  3. Sharp car!

    We did a similar swap about 5 years ago now to an 84 convertible. Swapped a 5.0 from an 87 LSC, but we swapped it to mass air at the same time. We also swapped the AOD with the engine. Made for a fun little car for her to drive while I drove mine.

    Anyway, I can't answer the EFI drivability with any kind of certainty. It almost sounds like a transmission issue by the way I understand the description of your problem. Manually shifting the transmission into first gear when leaving a stop sign would tell you for sure.
  4. @lLILCBRA Thank you. I love the black and gold combo on yours.
    what headers are you using. Any fitment struggles?

    I have tried manually shifting And doesnt seem any different.
    I guess a better way to put it would be like plugged cats during
    take off. After 20 it seems fine. I do not have cats btw.
    its driving me nuts though. I have found a local shop that is pretty good with
    diagnosing things like this. If I find out what it is I will update this in
    case someone else has a similar issue. I hate when threads end with
    no conclusion.
    The things we do for toys !
    #4 Donald Vincent, Jul 17, 2017
    Last edited: Jul 17, 2017
  5. Thanks!
    The headers are old Blackjacks iirc. They aren't made anymore and no one makes any like them to the best of my knowledge. For my application, I had to grind away a reinforcment rib on the bell housing to clear one of the tubes and some slight massaging to make room for the clutch fork. There were no fitment issues for the car itself.

    It'll be interesting to hear what your issue is. To me, it sounds like a transmission problem somewhere. I don't know why you'd have a problem with it if all you did was an engine swap, but that's what it sounds like to me....
  6. Wait.... just out of curiosity, what flex plate and converter are you using? The Lincoln 5.0 and your original 302 are balanced differently and would require their respective flex plates. I'm not sure, but I don't know if the II converter would bolt to the 5.0 flex plate, and the 5.0 flex plate shouldn't fit the II housing. So, if you're using the II flex plate and converter, you'd have other issues besides the transmission feeling sluggish from the start. I'm sure that's something you have already taken into consideration but didn't post, so I thought I'd ask. The reason being is I think the AOD converter is a locking converter, so if you have that in your car, that could be the source of the problem......
  7. Sorry it took so long. No updates as of yet. Got busy with grown up stuff. I hate that.

    I am using the original c4 ii torque converter and have the proper weighted flywheel from art carr.

    I am getting flack about not having the kick down connected. Some are insisting it has to be. So I'll do it to shut them up. Even though I can not see how or why it would matter. I was going to do it eventually anyway.