Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Understanding intake manifold principles.

  1. Nov 6, 2006 #1
    Hi there, hope someone is able to help me. I am trying to find some info on early intake manifold designs, for Ford 4 cylinder engines, otherwise known as the T-, A- and B- engines. These engines came standard with two intake manifold inlets, and 4 exhaust manifold outlets cast into the block.
    I have found lots of pictures of after-market dual-carburettor manifolds. These used dual intake runners, with two general systems. In the first system, the carburettors mounted on a common plenum, which then opened into the intake runners. In the second system, the carburettors were mounted at the top of the intake runner, with a cross-over pipe linking the intake runners.
    Does anyone know the theory behind this cross-over pipe, or seeming balancing of the intake runners? Is one more effective than the other? Can anyone point me to a source that might explain the principles?
    Bret W.
  2. jcsd
  3. Nov 6, 2006 #2


    User Avatar
    Science Advisor
    Gold Member

    Sounds like it's just a balancing pipe, equalising pressure in the runners to ensure that the cylinders are inducing the same quantity, and mixture, of inlet charge.

    Do you have any pictures of the arrangements?
  4. Nov 6, 2006 #3


    User Avatar
    Science Advisor
    Homework Helper

    Don't know the Ford engines, but I've dealt with seperate plenum systems on other engines.
    It was a real headache to syncronize the carbs.

    Perhaps the crossover was intended to reduce the syncronization problem as brewnog suggests.
  5. Nov 6, 2006 #4


    User Avatar
    Science Advisor
    Gold Member

    I've got a Ford engine (1960s design) using two twin-choke carbs, so there is a plenum for each pair of cylinders. As a result, cylinders 1 & 2, and cylinders 3 & 4 are balanced, but it can be quite a pain to balance the two pairs. The original carburettor on the engine had a single plenum, and single carb feeding all four cylinders on a common manifold. Much easier to set up, but not nearly the same flow.
  6. Nov 7, 2006 #5
    I think you are on to something there brewnog. I seem to remember reading something similar about crossover pipes in exhaust systems blancing the pressure.

    I am planning to build a dual-carb manifold, but thought i would try to understand the principles before i added anything to the design unnecessarily! Like i said, a lot of the aftermarket stuff was twin-carb items, most developed in the 30's, 40's and 50's, when there wasn't a wide range of different flow-rate carbs to choose from, like we have today. So, those clever guys realising that the more air/fuel mix available, the more potential energy, started adding multiple carbs.
    So, my aim is to emulate that basic idea, but using more modern (60's) carburettors.
  7. Nov 7, 2006 #6


    User Avatar
    Science Advisor
    Gold Member

    Mmm, twin choke Weber DCOEs maybe?

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Understanding intake manifold principles.
  1. Ducted fan intake (Replies: 6)

  2. Help understanding (Replies: 2)