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What is word from on high in regard to vacuum tuning?

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  • What is word from on high in regard to vacuum tuning?

    Read a variety of posts on vacuum tuning ProFlo 4 here. Some say great go for it, others don’t worry won’t get you much, granted both could be true. For an engine that is running well is it worth doing? I made some quick changes on mine, idle timing, and it went from -16.2 to -18.9 in a linear fashion from the starting point of 15 degrees up to 40 degrees in 5 degree increments (which got me the -18.9). Overall is set to 35. Didn’t play with that.

    I haven’t tuned this before at all. The default was 15 degrees on idle and that gets a manifold vacuum of sourness -16.2”.

    Around 35 the idle climbed on it’s own a little. I assume this means the IAC was no longer able to hold it down, but didn’t check that.

    Thoughts on what I should do?

  • #2
    If it ain't broke, then don't fix it.

    In general:
    Most people who put a new carburetor on their motor have a 50% chance of getting it right the first time.....the carb is too big/small, the camshaft is too big/small, they follow the advice of some one who has only installed 1 carburetor and it's on a motor that's way different then your own.

    VS.

    Most people who put a "Edelbrock EFI System" on their motor have a 85% chance of getting it right the first time.....the other 15% bought to big/small injectors, did not follow the instructions, using slip joint exhaust system, have mechanical issues with their motor ( loose timing chain, vacuum leaks, using wrong sparkplugs, burns oil ).

    As for tuning:
    You go for smoothest running motor first.
    Then you can use vacuum tuning to fine tune it.
    In my neighborhood, if you open your hood to check your oil, and the vehicle still runs after you close it.......Then your labeled the Neighborhood Mechanic.
    https://forums.edelbrock.com/filedat...?photoid=42773

    Comment


    • #3
      Originally posted by sunny2020 View Post
      Read a variety of posts on vacuum tuning ProFlo 4 here. Some say great go for it, others don’t worry won’t get you much, granted both could be true. For an engine that is running well is it worth doing? I made some quick changes on mine, idle timing, and it went from -16.2 to -18.9 in a linear fashion from the starting point of 15 degrees up to 40 degrees in 5 degree increments (which got me the -18.9). Overall is set to 35. Didn’t play with that.

      I haven’t tuned this before at all. The default was 15 degrees on idle and that gets a manifold vacuum of sourness -16.2”.

      Around 35 the idle climbed on it’s own a little. I assume this means the IAC was no longer able to hold it down, but didn’t check that.

      Thoughts on what I should do?

      Thoughts on what I should do? Call the Techline 800-416-8628 to discuss
      Don't get too caught up in the numbers.
      Just give the Engine what it wants &
      Let the numbers be what they are.

      Jim McFarland....

      Comment


      • #4
        I will call in. Does the standard program holding -16.7” at idle vs being able to reach close -20” imply that tuning is worth doing?

        Comment


        • #5
          I know not that simple as on the EFI this is just idle not cruise or WOT.

          Comment


          • #6
            Anyone? Thoughts. . .

            Comment


            • #7
              No additional thoughts from Eddlebrock on this? Popping at deceleration fuel cut-off also seemed to go down as I advanced the timing. Basic question unanswered here is that the car runs fine but by advance timing at idle I can go from -16.4" at 15 degree advance to -20" at 36 degree advance. Car runs well at both conditions from what I can see. Does this mean I should adjust this or not? Does the vacuum change mean anything on Pro-Flo 4 or should I ignore that??

              Comment


              • #8
                Originally posted by sunny2020 View Post
                No additional thoughts from Eddlebrock on this? Popping at deceleration fuel cut-off also seemed to go down as I advanced the timing. Basic question unanswered here is that the car runs fine but by advance timing at idle I can go from -16.4" at 15 degree advance to -20" at 36 degree advance. Car runs well at both conditions from what I can see. Does this mean I should adjust this or not? Does the vacuum change mean anything on Pro-Flo 4 or should I ignore that??
                What engine?
                Vehicle make & model?
                What MAP # is it on?
                Fuel pressure ?
                Hot engine idle vacuum?
                Injector size ?
                HP level ?
                Spark control settings ?
                Don't get too caught up in the numbers.
                Just give the Engine what it wants &
                Let the numbers be what they are.

                Jim McFarland....

                Comment


                • #9
                  Blueprint 347
                  Early Bronco
                  5009
                  48psi (I'll double check)
                  -16.4"
                  420hp
                  15 degree on idle 36 degree on total at 3,000rpm
                  Injector size I don't remember. Can check, was sized by you guys for this engine.

                  Comment


                  • #10
                    Map 5009 requires 58 psi , so dbl check that psi, adjust if needed.

                    Spark control " idle spark " bump up to 21 degrees for that cam, 36 Total timing is Ok.

                    Verify injector color band is white for 29 lb/hr.
                    Don't get too caught up in the numbers.
                    Just give the Engine what it wants &
                    Let the numbers be what they are.

                    Jim McFarland....

                    Comment


                    • #11
                      I'll double check the PSI and injector type. I had made the jump to 20 yesterday to see how it runs. Fine so far, less pops and burbling under deceleration at fuel cut off. Still sounds good.

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                      • #12
                        48psi. the regulator was reccomended by you guys. Not adjustable. Should I swap it out? If I do should I restart with a clean MAP?

                        I have 29lb injectors.
                        Attached Files

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                        • #13
                          Preset rail mounted regulators are either 43 or 58 psi.
                          If you find it runs better on different MAPs , & you are unable to get the SHFT #s into single digits , you may need to swap it out .
                          Last edited by 2700 Cast; 04-22-2021, 08:24 AM.
                          Don't get too caught up in the numbers.
                          Just give the Engine what it wants &
                          Let the numbers be what they are.

                          Jim McFarland....

                          Comment


                          • #14
                            Since it is running at 48 would you assume this is a 43 PSI regulator that is running high or a 58 running low? What other MAPs should I try on this engine?

                            Comment


                            • #15
                              And any reccomendations on pressure regulator for this type of installation?

                              Comment

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