Vacuum Hose From Distributor To Carb. 1972 Chevelle

Posted in Ignition Systems | Asked on May 23, 2010

Hey, I installed my HEI MSD Street Fire Distributor about a month ago. Haven’t driven the car since because I have been working on other parts of the motor. About a week later, my buddy and I took off the carb to clean it and replace some parts on that. Yesterday, we connected the carb back up but it seems like we lost the vacuum hose that goes from the vacuum advance on the distributor to the carb. We can’t find it anywhere. My question is: What is that for? Do we need it? What happens if we just plug the ends so no air will get in there and won’t mess anything up? And finally, how do you know if you will need to have that hose? I know about the vacuum advance on the distributor but not really sure what vacuum hoses do. Any info would be awesome. Thanks

There are 6 Answers for "Vacuum Hose From Distributor To Carb. 1972 Chevelle"

  1. joel95ex says:

    you have to have it….. the vacuum from the carb is what advances the timing

  2. wrenchbender says:

    replace the hose. it allows the spark advance to stay with the power curve of the engine. (short answer here). put another one on

  3. tallbrian1000 says:

    Vacuum advance mostly retards the timing when the engine is off so you can start the engine with out it backfiring.
    Once the engine starts it the vacuum moves the point mounting plate to the proper position for running.

  4. RBH Automotive says:

    Actually the vacuum line is what retards the timing. When you nail the throttle at low RPM you lose you manifold vacuum until higher RPM. The lack of vacuum allows it to retard the timing until the vacuum recovers and the centrigul weights in the distributor advance the timing on a curve.
    With the proper setting you can run without this and never care. The main thing is to be sure you don’t gt any spark knock under a high load, like from idle to hard throttle in gear.
    Your kit should have come with the caps to eliminate this and a small piece to lock it out.

  5. dodge man says:

    you need to have vacuum on it,try finding the port that has ported vacuum on it it will run real good on that port one will have constant vacuum on it and the other one will be partial vacuum,if you use the one for ported vacuum and it doesn’t run good try switching it,without having vacuum on it, it wont advance the timing and it will cause it to hesitate and possible have a back fire in it,i run constant vacuum on mine and it does real good,good luck with it.

  6. gearhead4 says:

    I strongly suggest you install the vacuum advance hose.
    Your Chevelle will run without it, but the performance will suffer.
    The vacuum advance causes the breaker plate in the distributer to rotate when high vacuum occurs. As the breaker plate rotates the ignition timing advances alowing the engine to produce more torque.The high vacuum occurs when you are accelerating or puting a greater load on the engine.
    Newer vehicles have vacuum sensors that send a signal to the engine control module (engine control computer) so that it can advance the ignition (spark) timing.
    A loose vacuum hose will also allow excess air to enter the carburetor (vacuum leak), which wil lean out the fuel/air mixture. This usually causes the engine to idle roughly.
    So find a hose and install it. Any auto parts store worth a hoot will have vacuum hoses. Even hardware stores have hoses that will do the job.

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