Compression Test done. Here are numbers.. HELP

Discussion in 'Fox 5.0 Mustang Tech' started by UnderPressureGT, Jun 10, 2003.

  1. This summer i wanna aim for a heads/cam/intake combo and i noticed my car has blue smoke under hard accel.... runs pretty strong though soo i did a compression test anyways.. Here are the results

    Cylinder 1- 120
    Cylinder 2- 125
    Cylinder 3- 125
    Cylinder 4- 125
    Cylinder 5- 100
    Cylinder 6- 115
    Cylinder 7- 115
    Cylinder 8-115

    Cylinder 5 seems a bit lower then the rest.. do i have a bad ring or something?? Im not sure if i did the test right but, the engine was warm, i took out all plugs and cranked the motor over with no throttle..

    I wanna build a nice h/c/i combo, but seeing them results, im not sure if it will be worth it??? Can i get some advice here??

  2. All you numbers look low to me. When I did my compression test, my numbers were all in the 170-180psi range. Looks like it's time for a rebuilt or a crate motor. :mad:

  3. hey man crank the motor over at least 4 full times and hold the throttle open annd then tell us your numbers I bet they go up
  4. At what point are compressions numbers bad? What are stock compression numbers? I'm doing the test soon before I do my h/c/i combo.
  5. i had the engine crankin till i got the highest number.... it will make a difference with the throttle open?

    I just dont see how its time for a rebuild YET.. im not loosing any power.. motor runs real strong... pretty fast for a stock 5.0 ide say... It just blows out blue smoke on hard accel
  6. You should be at the least around 145 for a 5.0L to say your engine is in good shape. Those numbers are low, which mean's something is wrong and probably time for a rebuild. I've seen alot of high milage 5.0L spec at 165-175 Compression which is great and where you should be. I had a 5.0L a while ago that had over 195,000 Miles on it and it averaged 170. Holding the throttle wide open dosn't do anything for compression numbers, it just prevent's the car from flooding. Looks like it's time for a rebuild dude. Just insure you turn the car over at least 4-5 Times to insure a correct reading.
  7. The blue smoke tells a tale before you even got the numbers; if you add h/c/i without freshening up the bottom end, you'll only speed up the demise of the bottom end. You'll need a complete rebuild or a crate short block as suggested above.