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No suction on intake stroke

Discussion in 'The Hokey Ass Message Board' started by inlineNmine, Jul 11, 2013.

  1. inlineNmine
    Joined: Oct 3, 2011
    Posts: 19


    I just received an old chrysler 250 flathead 6. When turning it over, there is no suction through the intake manifold. The Valves are new and seated well. I was wondering if the timing chain/gear was installed 180 degrees off, if this could cause the problem? I think that on the power stroke it is blowing air through the intake/carb. There is never any suction at the intake side, but there is suction through the exhaust manifold; this is what leads me to believe that the cam is not synched to the crank properly. Do you believe this is a timing gear issue? Any help would be appreciated. Thanks :confused:
  2. Dirty Dug
    Joined: Jan 11, 2003
    Posts: 3,678

    Dirty Dug

    It sounds like timing, you may be 180 out.
  3. bcowanwheels
    Joined: Feb 22, 2010
    Posts: 321


    Yep or you got a crack somewhere
  4. tassiepete
    Joined: May 13, 2013
    Posts: 54


    ummm, how do you install a camshaft 180 deg out?

  5. saltflats
    Joined: Aug 14, 2007
    Posts: 10,843

    from Missouri

    Does it have compression?
  6. 51 Leadsled
    Joined: Nov 23, 2007
    Posts: 954

    51 Leadsled
    from NC

    Squirt some oil in the clyinder through the spark plug holes.
  7. Devin
    Joined: Dec 28, 2004
    Posts: 2,351

    from Napa, CA

    Could the engine be rotated in the wrong direction ie. marine engine? Would that even matter?
  8. StLouisSled
    Joined: Feb 9, 2008
    Posts: 119


    Agreed...this would be a good place to start. Check the compression.
  9. J scow
    Joined: Mar 3, 2010
    Posts: 489

    J scow
    from Seattle

    This sounds likely to me. Or he is just turning it the wrong way.
  10. J scow
    Joined: Mar 3, 2010
    Posts: 489

    J scow
    from Seattle

    There should never be suction from the exhaust. Could be cam timing.
  11. This can be done if you dont align the timing marks on the gears.Duhhhh
  12. terryble
    Joined: Sep 25, 2008
    Posts: 541

    from canada

    I would go with make sure you are turning the crank the right direction, clockwise, that is if you aren't using the starter. If you are turning it on the starter and have no intake suction you do have a bigger issue, quite likrly cam related I had a similar issue with a 230 gear on a 235 cam. Gear is the same and presses on to the 235 cam but timing marks are positioned differently.
  13. Search Dog
    Joined: Oct 30, 2012
    Posts: 112

    Search Dog
    from Western CT

    How about valves stuck open?

    Had that happen with my old JD tractor when I ran avgas for a while. All the lead clogged up the valve guides and the valves stuck open.

    D'Oh! Just read the part where you said the valves were new. How much was disassembled when the valves were done? Was the cam removed?
  14. Koob
    Joined: Jan 14, 2008
    Posts: 134

    from Bryan, TX

    The cam cannot be 180 out if the timing marks were aligned either together or 180. If the cam is out of time then it must be 90, 45, 20 whatever degrees out but not 180 that is only needed for distributor placement. (Refering to a SB V-8)
  15. terryble
    Joined: Sep 25, 2008
    Posts: 541

    from canada

    If the valves are stuck open you won't get suction on the exhaust side as discribed.
  16. the cam turns 180 degrees for every 360 degrees of crank rotation - can't be 180 out.
  17. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,593


    Your theory doesn't work.

    If the cam is 180 out the cam be opening the wrong valve on the wrong stroke.

    Intake =intake valve open piston going down.
    Compression both closed piston going up
    power = both closed piston going down
    Exhaust= exhaust open piston going up.

    That isn't counting any overlap just the theory of what is happening in the engine.

    Turn the cam 180 out and you have the intake open when the piston is going up and the exhaust open when the piston is going down. In theory that changes the engine so that the intake works as the exhaust and the exhaust works as the intake.

    InlineNmine are you turning it over by hand or with the starter? turning it over by hand may not turn the engine fast enough to be able to notice any air going into the intake.
  18. Mr48chev
    Joined: Dec 28, 2007
    Posts: 29,593


    As far as how someone could get a cam 180 out it isn't that hard when they have been working on one design of engines most of the time and run into one one that has the timing marks in different spots. and then throw in some models of Ford sixes for good measure to really mess with their minds.
  19. sunbeam
    Joined: Oct 22, 2010
    Posts: 5,277


    If the cam is 180 out turn the engine one more turn.
  20. chevyburb
    Joined: Apr 17, 2006
    Posts: 169


    Shouldn't the valves be banging the tops of the pistons with the cam out of time that badly???
  21. terryble
    Joined: Sep 25, 2008
    Posts: 541

    from canada

    That would be difficult in a flathead motor
  22. propwash
    Joined: Jul 25, 2005
    Posts: 3,858

    from Las Vegas

    some of you guys are getting ahead of yourselves. The cam can be 180° out, given that the cam rotates a full 360° (leave the relationship of the crankshaft out of this), as does anything that's round that you turn from start back to the starting point again. If you turn the camshaft halfway around, that makes it 180° "out" of phase. Everything that is round and rotates can be 180° out. Makes no difference how many times the camshaft turns for each rotation of the crank, the cam itself can simply be installed improperly (at its ½ rotation point).
  23. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771


    can't happen on a flat head...the valves aren't over the pistons.
  24. mart3406
    Joined: May 31, 2009
    Posts: 3,055

    from Canada

    An automotive cam installed 180
    degrees out of synch....or you've
    got a reverse-ground cam intended
    for a reverse-rotation marine
    application that's installed right
    on the marks.
  25. Lobucrod
    Joined: Mar 22, 2006
    Posts: 4,122

    Alliance Vendor
    from Texas

    Time for a new ole lady!:eek:
  26. R Pope
    Joined: Jan 23, 2006
    Posts: 3,309

    R Pope

    The old 180 out story again!!?
    Guys...Put the cam in time with the crankshaft mark up, and the cam mark down. Right? Okay, now turn the crank one full turn. Omigosh! The cam mark is now straight up, or 180 degrees out! What to do, what to do??? Tear it off and turn the cam a half turn?
    Don't be silly. Finish putting it together and fire it up.
  27. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,582

    Rusty O'Toole

    The cam can be out of time but not 180 out. Worth checking anyway.
  28. inlineNmine
    Joined: Oct 3, 2011
    Posts: 19


    The motor is an industrial engine out of a forklift. It's a 236 block with a 250 crank in it. I am not sure if the cam was ever changed when the new crank was installed. I am turning the motor over with the starter motor. I believe the compression will check out fine, as it had good cross hatching, little cylinder wear, and new rings. The problem is as mr48chevy called it, my intake has now become an exhaust, and my exhaust has become my intake. I believe i need to tear into the timing cover and change the crank to cam relationship. Mart3406 do you know if the industrial engine applications are reverse-rotation? If so, can the automotive cam be used in these industrial applications? my motor is turning clockwise when using the starter, as is the rotor. thank you for the help so far.
  29. Well a forklift drivetrain is backwards as in going forward is away from the radiator.
    There's quite a few engines out there with the intake bolted to the exhaust flanges. So it's possible
  30. mart3406
    Joined: May 31, 2009
    Posts: 3,055

    from Canada

    All the Chrysler industrial engines
    I've ever seen were standard
    rotation, but with Chrysler, anything
    is possible. If some, even small
    manufacturer needed a an engine
    that spun in the opposite direction
    for some type of machine or
    equipment they were building and
    selling, I'm sure that Chrysler would
    facilitate their needs and supply
    such an engine. They could do it
    quite easily too, simply by
    substituting the standard industrial
    cam with one of their 'off-the-shelf '
    reverse rotation marine versions. By
    the way, the Chrysler industrial were
    built in the same plant as the marine
    engines and marketed by the same
    in-house sales group - ie - "Chrysler
    Marine and Industrial Division"
    If by chance your engine has been
    fitted with a marine cam ground for
    reverse engine rotation - either
    intentionally when new or possibly
    accidentally when it was rebuilt and
    had the crank swapped before you
    got it, you should be be able to simply
    swap the cam for a conventional
    automotive one. Check the distributor
    and/or the distributor drive gear..
    Either the distributor and/or the
    drive gear might (or might not)
    also need to swapped for a standard
    automotive type as well.

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