Compression 175psi, is this too high on a 15.5 vanguard?

Discussion in 'Mechanic and Repair' started by shopteacher, Jul 3, 2006.

  1. shopteacher

    shopteacher LawnSite Member
    Posts: 60

    Hey guys, hope all is well.
    I had only 70 psi on a briggs vanguard ohv. I replaced the head gasket and now its a whopping 175. I adjusted the valves to .005 and .007 respectfully. But WOW, I didn't think I would get 175 psi.
    Any thoughts?
     
  2. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613

    175 is a little too high I believe. Sounds to me like you need a thicker head gasket to bring that down to around 160.
     
  3. Restrorob

    Restrorob LawnSite Fanatic
    Posts: 11,022

    How does it run now with the new gasket ? And sorry maniac, There is only one gasket for this engine.
     
  4. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613


    Well, thats gonna suck if it doesnt run right :hammerhead: vanguard...
     
  5. shopteacher

    shopteacher LawnSite Member
    Posts: 60

    I found the problem. I had a briggs mechanic tell me that 180 lbs was what a brand new engine would have. Long story short - I took off the valve cover and discovered the rocker arm had come off.
    I don't know how, but I adjusted the valves again, and it ran great
    This time the compression was 85
    Good lesson.
    Thanks for your answers.
    Keep on wrenchin'
     
  6. lawnmaniac883

    lawnmaniac883 LawnSite Silver Member
    Posts: 2,613


    If the exhaust rocker is the one that came off then the engine would act like an air compressor. My guess is that you turned it over twice allowing it to build excess pressure. Now 85? Too low... engine wouldnt be running if it only had 85 PSI.
     

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