Exhaust sucking in

Discussion in 'Street/strip 400/430/455' started by 1970stage1455, Nov 12, 2019.

  1. 1970stage1455

    1970stage1455 Well-Known Member

    As most of you know I'm putting the kenne bell find back together and I'm to the last touches. I still have to put on the b4b intake and some other odds and ends how ever if i turn it over with the start ( it turns very slow I will be getting a high toque starter ) the exhaust port will suck inwards ( I put my hand over it ) also blows out depending on the stroke same for intake it will push air out and suck in depending on stroke of the engine is that normal or is there something going on with it
  2. TrunkMonkey

    TrunkMonkey Well-Known Member

    Slow turnover and a long duration cam event can exhibit that behavior.

    "At running RPM", the events still occur, but the momentum of the flow is able to overcome the effect.
    1970stage1455 likes this.
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Lots of overlap, both valves are open at the same time so you might see that at low RPM.
    1970stage1455 likes this.
  4. Stevem

    Stevem Well-Known Member

    A fully normal accurace!
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  5. 1970stage1455

    1970stage1455 Well-Known Member

    Thank you guys, I was kind of worried
  6. Stevem

    Stevem Well-Known Member

    If you need further proof of this here it is.
    Have you ever been on the road next to diesel truck and they let off the gas and the turcks Exh sound get 6 times louder then what it was?
    That's called a jake brake and what it does is a blade closes off the Intake flow to the motor so the Pistons back suck air in thru the trucks Exh system.
    Yes, diesel motors are not throttled by means of restricting air like a Carb on a gas motor does with throttle blades, a diesel motors rpm is changed purely by the amount of fuel that's injected into it!
    1970stage1455 likes this.

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