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308 Engine Compression

Discussion in 'Tuning' started by bfhoon, Mar 13, 2018.

  1. bfhoon

    bfhoon Member

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    Hi Everyone

    Long story short I have a vk with a hq 308 red motor in it. It was an ex turbo blo thru turbo but Ive bought it minus the turbo.

    Bit of a background
    Red 308 hq motor
    red heads pre pollution
    750 holley vac secondary
    torque power single plane hi rise manifold
    straight cut timing gears
    gilmer belt driven
    Unknown if it has a cam probably
    Crane Hi 6 fireball ignition system with lx coil
    4 speed m21
    4.11 diff gears.

    Runs heaps fuelly in my garage it stinks the place out.

    I did a compression test and got the below results I did it with the engine warm and all the plugs out

    Cylinder
    1. 145 psi
    2. 125 psi
    3. 150 psi
    4. 125 psi
    5. 115 psi
    6. 120 psi
    7. 115 psi
    8. 125 psi

    Ive set te initial timing pretty high about 20 degrees and tuned up the carb the best I can. The best ever vacuum reading I can get is 11-10 hg it bounces around a bit. The motor shakes a tad but nothing heaps serious. Am I wasting my time getting a smaller carb and would my compression results be indicative of a shaly motor. I have a pcv breather catch can and you can see it smoking after the cars been driven and sometimes while idling. I know the compression results arent the best but I didnt think they were all that bad either.
     
  2. Smashfist

    Smashfist Active Member

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    What jet size is in the Holley? If it hasn't been changed since the turbo came off it's likely the jet size is way too big for an NA setup on the same engine.
     
  3. Smitty

    Smitty Well-Known Member

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    compression is crap....
    max difference between highest and lowest is 10% for a good engine
    they ain't... :(
     
  4. immortality

    immortality Moderator Staff Member

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    I think this is the same thread as one on the AV8 forum which I think covered it quiet extensively.
     
  5. VR38

    VR38 Well-Known Member

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    Was the throttle WOT?
     
  6. Deuce

    Deuce Super Stock

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    Please stop saying it has this ^ ^
    It's not a 202, your 308 does not have straight cut gears anywhere in it!!!!
     
  7. VR38

    VR38 Well-Known Member

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    Not even the ring gear?
    Oil pump?
     
  8. Deuce

    Deuce Super Stock

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    Lol, i thought about that afterwards, but standby my comment. Oil pump is external bolt on, so is flexplate. And i said in.
    Also the op said straight cut timing gears which they are not.

    The closest straight cut 'timing gear' would be the ABS reluctor ring on the front hub/diff.
     

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