Manifold Vacuum

Discussion in 'General Automotive Questions' started by Matt Winters, May 18, 2020.

  1. Matt Winters

    Matt Winters In First Gear

    Messages:
    20
    I have a 1970 F100 with the 390 and an Edlebrock carburator. It needs a tune up, but I cannot find a place to hook on my vacuum guage. No power brakes, so I can't use that vacuum line. In fact, this truck has NO vacuum lines beside the vacuum advance. It appears as though there is a port behind the carburator, but how I'd hook my guage up to it I do not know.
     
  2. beerbelly

    beerbelly In Maximum Overdrive SILVER MEMBER

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    If your carb is anything like mine, there are 3 vacuum ports on the front of the carb. I think I used the left one to hook up my gauge.

    EDL-1403.jpg
     
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  3. burninbush

    burninbush In Maximum Overdrive

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    near SF
    Well -- manifold vacuum is the same no matter where you find it. But in your situation I assume you could just disconnect the line to the distributor and put your vac gauge there.
     
  4. pmrphil

    pmrphil In Maximum Overdrive GOLD MEMBER

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    central CT
    Providing that is manifold vacuum, and not ported vacuum, like many distributors use.
     
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  5. rancheromac

    rancheromac In Third Gear

    Messages:
    165
    on Edlebrock, you have outlet for ported vac(left), full time(right) and PCV valve port(middle big one)
     
  6. beerbelly

    beerbelly In Maximum Overdrive SILVER MEMBER

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    I spoke to someone much wiser than me, and found out I was using my vacuum gauge on the wrong port on my fairly stock 289 with stock vacuum advance distributor. I should have disconnected & plugged the timed vacuum port on the left, and attached the gauge to the manifold port on the right (this is normally plugged). Thanks Phil.

    I'm sure many or most of you know this, but I didn't. I'll give it a try tomorrow.

    EDL-1406_xl.jpg
     
  7. Clark

    Clark In Maximum Overdrive

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    Years ago I watched my Dad add a hydroboost power brake booster to my 1955 Merc. He drilled a hole in the 292 cid Y-Block intake manifold with a greased drill bit. The grease was to catch the chips. Then he tapped the hole - NPT pipe tap - for a barbed fitting to match the hydroboost vacuum hose. I would think you could always do this.
     
  8. beerbelly

    beerbelly In Maximum Overdrive SILVER MEMBER

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    Woo Hoo! I'm getting a nice steady 20.5 inches on the gauge after adjusting the mixture screws. I remember last time I did this (on the wrong port) I was getting a flickering 15 or so.
     
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  9. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    11,154
    Location:
    Seguin, TX
    20.5" is excellent! Good show!
     

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