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  1. #11
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    Exactly on the '96 and newer it's one per header, but they're in the "Y pipe"

  2. #12
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    Peter, I asked if there were any modifications made....Propane is a big modification.....lol :mrgreen:
    From what I understand you should expect a lower km/litre when using propane on this engine.
    Did you determine if this poor engine performance was due to the intake manifold gasket, or something else.

    Does your impco system even use the feedback computer, and is it running off of a signal from the O2 sensor?

    This poor engine performance could be a whole new set of problems that we never would have discussed if we never knew you were running propane.

  3. #13
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    Hi Patrick,

    The problems that I have are also on gasoline.
    And when it runs bad on gasoline it also runs bad on propane.

    You call propane a big modification :mrgreen: , around here itís a normal thing due to the high taxes on fuel.

    When I run on propane everything from the motor management is disabled thatís normal for an Impco installation itís not the best way to go I understand that.
    Peter Smet
    Haasdonk, Belgium

  4. #14
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    I didn't think propane was so common over there. I can see why it would be. It's so much cleaner.

  5. #15
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    Was the problem/ poor performance due to the coolant leak in the intake manifold?

  6. #16
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    After fixing the leak the performance is a little bit improved.
    Itís a strange behaviour one time the suburban is slow the other time fast.
    Maybe I am looking in the wrong place; it could be the automatic transmission. I donít know.
    :?:
    Peter Smet
    Haasdonk, Belgium

  7. #17
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    Is it like that with both fuels?

  8. #18

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    When you say that it's slow sometimes and fast at other times. Is this noticable? I had this happen before from an intake manifold leak on an old 350 4-bolt. Ended up leading to a cracked block. :-(

    Steve
    10 Chevy Traverse LT AWD
    02 Chevy Trailblazer LS (110K+ miles - loaded except for 4WD - WRECKED!)
    99 Chevy Cavalier LS (105K+ miles - commuter car)
    78 Chevy Suburban Silverado (454, 3/4 ton)
    62 GMC 3/4 ton Pickup (350 police interceptor)

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  9. #19

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    That was a 1973 350 4-bolt police special that I had too. :-(

    Steve
    10 Chevy Traverse LT AWD
    02 Chevy Trailblazer LS (110K+ miles - loaded except for 4WD - WRECKED!)
    99 Chevy Cavalier LS (105K+ miles - commuter car)
    78 Chevy Suburban Silverado (454, 3/4 ton)
    62 GMC 3/4 ton Pickup (350 police interceptor)

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  10. #20
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    @TrailLeadr The performance is better on petrol, but thatís normal you can say itís on both fuels the same problem it can run great for a couple of days and then itís back to pour performance. :(


    @Steve I already changed the joint from the intake manifold there was a little improvement there.


    The reason that I am thinking on the transmission is because when I hit the gas the rpm goes up for about 600 rpm before the transmission kicks in. Maybe thatís normal I donít know itís my first Suburban.
    Peter Smet
    Haasdonk, Belgium

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