350 Falls on it's face
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350 Falls on it's face

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    I'm No Expert Shaun's Avatar
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    Default 350 Falls on it's face

    I have a buddy with a old Nova, has a SBC 350 in it, pretty much stock from what we can tell. The other day he said it started acting up where if he jumped on the throttle he claims it would "shake alot and go no where". He said if he rolled into it slowly it would get going. How today he's saying that if he mashes the gas it is just falling on it's face and almost dies. He said if he rolls into it it's fine though, says it takes about 3-5 seconds to roll into the throttle slow enough to get to WOT. I ran a quick test on his vacuum advance and verified it's at least holding vacuum and changing the advance. I'm wondering what else might be going on here. He's changing the rotor and cap right now.

    Any ideas?

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    Bad accelerater pump? Plugged fuel filter?

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    New here Beer:30's Avatar
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    First guess - - accelerator pump, carburetor.

    The accelerator pump shoots additional/immediate fuel into the air stream to counter-act throttle increase. The venturies will eventually catch-up and provide the proper mixture (or close) but won't provide additional fuel until the airflow pulls it in. So, there has to be instant fuel to add to the instant air during throttle opening(s).

    Yes, could be ignition related or combo of both. However, if the car sits alot, accel pumps tend to dry out and eventually disintegrate. When this happens, there is no fuel to counter-act the additional air from opening the throttle and the engine falls on it's face (so to speak) until the venturies catch-up.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    I'm No Expert Shaun's Avatar
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    I had thought about the idea of it being the accelerator pump but wouldn't that just cause a hickup for a second? I though the point of the accel pump is to just bridge the gap were vacuum is lost when hitting the gas. Also, if it was the accel pump wouldn't the problem also exist when wapping the throttle in neutral?
    Last edited by Shaun; 10-22-2012 at 12:49 PM.

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    Senior Member EVILFORCE's Avatar
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    Either a fuel supply problem or a ignition issue.
    No Fool Like A Old Fool is there?

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    New here Beer:30's Avatar
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    Quote Originally Posted by Shaun View Post
    I had thought about the idea of it being the accelerator pump but wouldn't that just cause a hickup for a second? I though the point of the accel pump is to just bridge the gap were vacuum is lost when hitting the gas. Also, if it was the accel pump wouldn't the problem also exist when wapping the throttle in neutral?
    If it's constant and never recovers, there are several things to check. The additional mention of fuel-filter is definintely another good place to look.

    I had one do something similar back in the day and it ended up being the LAST THING I replaced - - the coil. Also, a friend had an early Chevelle that developed a surge problem during cruise only. He kitted the carb (Rochester 2GC 2bbl), which didn't take it away. I loaned him a coil I had laying around and that fixed it.

    So, try a coil and see what happens. More is asked of it when requesting more engine RPM (accel) and it may not be up to the task. That's an easy swap.
    Last edited by Beer:30; 10-22-2012 at 12:57 PM.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


    2001 SleekCraft 30' Heritage SSB, open-bow mid-cuddy. 496HO / Bravo-I.

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    I'm No Expert Shaun's Avatar
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    He just called me and now it's doing it at idle. I had him verify the accel pumps are working and they are. Steady steam of fuel.

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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by Shaun View Post
    He just called me and now it's doing it at idle. I had him verify the accel pumps are working and they are. Steady steam of fuel.
    check the timing..full advance???

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    Senior Member ol guy's Avatar
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    what carb and how is the fuel pressure? Way to many reasons for this! Did this problem just start after a good running vehicle? how is the fuel filter? O.G.

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    sounds like carb to me, dumping too much fuel if u nail it, or not getting enough,

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    Senior Member EVILFORCE's Avatar
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    Its Ignition.
    No Fool Like A Old Fool is there?

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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by Shaun View Post
    Any ideas?

    What brand carburetor and part#?
    Dual Plane or single plane manifold?
    HEI, points, or other?
    Does it idle perfect?
    How old is the fuel?
    Is the engine stock? If not, what mods?
    Have there been any recent changes or modifications?
    Has the car ever worked as it's supposed to since he's owned it?

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    Senior Member SoldHondaBoughtHondo's Avatar
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    Quote Originally Posted by Budweiser View Post
    What brand carburetor and part#?
    Dual Plane or single plane manifold?
    HEI, points, or other?
    Does it idle perfect?
    How old is the fuel?
    Is the engine stock? If not, what mods?
    Have there been any recent changes or modifications?
    Has the car ever worked as it's supposed to since he's owned it?
    X2...10 replies and nobody even knows what carb/dizzy.....And you sound exactly someone who intends to offer some valid advice
    "A liberal paradise would be a place where everybody has
    guaranteed employment, free comprehensive healthcare, free
    education, free food, free housing, free clothing, free
    utilities, and only law enforcement has guns. And believe it or
    not, such a place does, indeed, exist: It's called prison."

    Sheriff Joe Arpaio
    Maricopa County Sheriff's Office

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    Or Seth, either one Budweiser's Avatar
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    Quote Originally Posted by SoldHondaBoughtHondo View Post
    X2...10 replies and nobody even knows what carb/dizzy.....And you sound exactly someone who intends to offer some valid advice
    I may not have the answer, but once we stop shooting in the dark and shed some light on the subject... someone will. A lot of smart guys here.

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