SBC woes.

Discussion in 'Engine Topic' started by Trashman, Mar 20, 2014.

  1. Trashman

    Trashman New Member

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    Ok long time listener first time caller, Im 22 and this is the first engine I have built. I may not have all the puzzle pieces yet to help you guys decode this problem, but hopefully I can narrow down the cause of the source of the problem.

    I have a 387: 2 piece 4 bolt main block, Malhe .040" over forged +5cc pistons that are supposed to give 11:1cr with 64cc heads, Forged Eagle 5.7" rods, Eagle cast Steel crank (3.75"). cant remember what i filed the rings to, I know one was .018". (Went off what a 70-71 hi po corvette 350 had in a old chiltons book. Pistons are .014-15 in the hole.
    Cam is comp cam .460/.460 lift, 110deg lobe separation with 218/218 dur at .050. Cam was previously in engine and properly broke in and has only 5000 miles on it.

    Heads are 76cc World Stock Replacements that were previously on engine. gaskets are .040"
    The valves leaked, but I lapped the valves and they did not leak before I put them back on. Carb is a carter 750 currently and manifold is a edlebrock performer intank . Distributor is a Pertronix flame thrower.
    Rotating assembly were all professionally balanced and sized for factory errors, cylinder walls were honed.

    I have yet to drive the car (still on blocks), Engine starts up and idles. Dad says it runs bad, Lazy throttle response, and blows fuel back out of the carb under load. Did a compression test with a old snap on set and Its design only allowed me to access 3 cylinders. and They were all over; 225, 170, 115. My dad thinks maybe we put the cam in a the Advance or retarded position. I dont know, maybe you guys might have an idea?
     
    Last edited: Mar 23, 2014
  2. fbody_mike

    fbody_mike Veteran Member

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    Wow, 225 on one cylinder and 115 on another is bad. How did you set the lash on the rockers?
     
  3. Trashman

    Trashman New Member

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    Hand tight + 1/2 a turn initially. Then It was running bad and all the pushrods were somehow loose so I tightened them again, maybe half turn again. I probably need to re adjust them before I pull the heads to see if it helps
     
  4. fbody_mike

    fbody_mike Veteran Member

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    By this, did you mean that this is solid lifter, or hydraulic lifter?
     
  5. Trashman

    Trashman New Member

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    solid, I will get the exact specs this weekend
     
  6. CamaroGP

    CamaroGP Veteran Member

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  7. fbody_mike

    fbody_mike Veteran Member

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    ^1, yes. I think you have some valves being held open, which is why the compression is all over the place, and idle is bad, plus the gas shooting backwards out the carb.
     
  8. Trashman

    Trashman New Member

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    Alright thanks guys. Ill re-adjust this weekend and see if it helps.
     
  9. CamaroGP

    CamaroGP Veteran Member

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    After adjusting the valves properly I suggest you do a compression check again. Just to make sure you had no valve to piston interference. Don't want any bent valves.
     
  10. hhott71

    hhott71 R.I.P 11/19/18 Lifetime Gold Member

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    Loosen all the rockers.
    Tighten each rocker so there is no up down loosness, rotate the crank an 1/8th turn and retighten any loose ones, turn it another 1/8th turn until you have at least 2 revolutions. Now add 1/2 turn to each rocker nut.
    The lash is set and won't need to be messed with again.
     

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