Engine Have A 5.0 Engine From An 89 Gt In My 68. Need Some Tips And Advice On Making It Run Smoother

Discussion in 'Fox 5.0 Mustang Tech' started by Tims97pony, Jul 1, 2013.


  1. Tims97pony

    Tims97pony New Member

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    ok, i have a 302 from an 89 gt installed in my 68 coupe. i just acquired this car last weekend and it has a few minor issues that i would like to hammer out. i am not an expert when it comes to carbureted engines, but will be learning as i go.

    the engine is built with the following components or so i am told.

    lower roller engine including heads, block , crank, pistons, etc.... non bored engine.
    weiand street warrior intake
    hedman ceramic full length headers
    demon carb with spacer, road demon 725 i think. dont know how to tell.....
    ford racing X303 cam
    MSD distributor, with ford racing wires, 6AL ignition control, and ACCEL coil.

    the problem i am having is that it tends to want to die at stop signs occasionally, although sometimes it idles fine. i idle it up slightly and it doesnt want to sit in drive without surging. (2500 stall) and also wants to die when in park as well. basically doesnt want to idle very well. it also has a slight miss when under hard acceleration, kind of a thump thump in the exhaust note. but it does run extremely well otherwise, pulls very hard and runs very, very strong.

    any tips or advice would be appreciated, im wondering if its just too big of a cam?
    can i jet the carb and improve all the issues?
  2. v8only

    v8only Active Member

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    that cam is way too big for those heads..stock roller cam works fine for those stock heads..the bottleneck is the heads..pull vacuum readings..check for vacuum leaks first..

    Sent from my SPH-L710 using Tapatalk 2
  3. Tims97pony

    Tims97pony New Member

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    yeah i was wondering if the cam was too big, but with stock valve size isnt it the same thing as a smaller cam with oversized valves?

    im actually wondering if it isnt a temperature issue, its hot as hell here and after i let it sit in the garage and cool down a bit it runs much smoother for a bit. and it seems to run much better at night when the ambient temp is lower. this is what made me think about jetting the carb. but ive never even opened up a carb, so i dont know much about em.

    vacuum leaks may be possible, ill definitely put the gauge on it and see what i get. although there is not much for vacuum lines, everything is electric, except to the transmission.
  4. v8only

    v8only Active Member

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    my carb runs the same at 110 degrees outside as it does at 70..my radiator temps never go higher than 195. id highly suggest picking uo a book on carbs..

    sounds like u can have any number of issues which is gonna take some troubleshooting

    Sent from my SPH-L710 using Tapatalk 2

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