Will to large of jets make engine overheat?

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  • steelkiwi75
    Senior Member
    • Sep 2007
    • 366

    #1

    Will to large of jets make engine overheat?

    I have a pro systems carb. I can't find paperwork on it. Believe it's about a 800 to 850 cfm. Jets are 76 front and 86 back . Engine starts to overheat 5 or 6 laps into feature and is always hard to start. Sometimes i have to hold pedal to the floor til it fires. Any feedback? This is on a 358 sas spec aluminum head motor. Thanks in advance
  • RacerX10
    Senior Member
    • Jun 2007
    • 571

    #2
    Originally posted by steelkiwi75 View Post
    I have a pro systems carb. I can't find paperwork on it. Believe it's about a 800 to 850 cfm. Jets are 76 front and 86 back . Engine starts to overheat 5 or 6 laps into feature and is always hard to start. Sometimes i have to hold pedal to the floor til it fires. Any feedback? This is on a 358 sas spec aluminum head motor. Thanks in advance
    Usually too small a jet (lean condition) is what causes over heating. Where's your timing at ?

    Vacuum leak could cause what you're talking about too, and would indicate as a lean condition (I think, I'm not an expert on such things). Have you gone over the carb really well looking for loose screws / bad gaskets / etc ?
    Last edited by RacerX10; 05-01-2016, 04:10 PM.

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    • perfconn
      Senior Member
      • May 2007
      • 3636

      #3
      Sounds like you have two problems.Too large of a jet will make it run cooler.Having to hold acclerator on floor to start indicates it is flooding.The overheating is another problem and could be anything from dirty radiator,belts slipping on worn out pulleys,wrong fan,fan not in right position,could be lots of reason to overheat but not too big a jet.

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      • gbeem
        Junior Member
        • Jul 2007
        • 8

        #4
        Make sure your squatters are squirting. Had this problem a few times.

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        • keeks
          Senior Member
          • Oct 2008
          • 687

          #5
          There will be a number stamped on the side of your carb. Go to www.pro-system.com and click on the "Ask the carb guy" link. Post your carb number and Patrick will tell you what your original build is. Then he can point you in the right direction.

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          • TALON75
            Senior Member
            • May 2007
            • 887

            #6
            Have you checked for retarded timing lately? The symptoms you describe would make me look there first. I would also take keeks advice, as I haven't ever seen jets that far off, could be the way it was built but if you can find out then that would be good piece of mind.
            www.RACE91.com

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            • let-r-eat
              Senior Member
              • May 2007
              • 2319

              #7
              I would double check valve adjustment, timing, and general tuneup items also.
              BUCKLE UP NOW, YA HEAR?

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              • steelkiwi75
                Senior Member
                • Sep 2007
                • 366

                #8
                No reply from pro systems yet. What would be y'alls suggestions on how much to lower jets?

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