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    Author Topic: Something weird going on  (Read 46558 times)

    Offline cudabob496

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    Something weird going on
    « on: August 19, 2016 - 03:54:46 PM »
    When my car is warmed up, then allowed to idle, the rpm will
    all of a suddent drop to between 100 and 300, that\n the engine
    will be shuddering. If I pump the throttle at that time, the engine
    will go back up to normal idle of 1200.  Then if I wait a while,
    cycle will repeat. Also, was getting the shuddering and idel around
    100 to 300 when trying to start the car to.  Not sure if its
    distributor related, or if I need to take the carb apart. Engine is 15 years old.
    Maybe something else is worn and needs replacing.  Out on the road, it runs fine.
    « Last Edit: August 19, 2016 - 07:48:58 PM by cudabob496 »
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000


    Offline cudabob496

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    Re: Something weird going on
    « Reply #1 on: August 19, 2016 - 06:11:54 PM »
    well, left a message with MSD tech, but in meantime,
    will take apart carb. Dirt in the idle circuits?
    « Last Edit: August 19, 2016 - 06:14:43 PM by cudabob496 »
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline Chryco Psycho

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    • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
    Re: Something weird going on
    « Reply #2 on: August 19, 2016 - 09:29:39 PM »
    Where to start , it could be fuel / carb or ign  need a whole lot more diagnostic to even start on this one
    Logged

    Challenger - You`ll wish You Hadn`t

    Offline cudabob496

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    Re: Something weird going on
    « Reply #3 on: August 19, 2016 - 10:43:32 PM »
    interesting, pulled carb, and carb gasket on top of intake had wet gas in the front.
    And before lifting carb off intake, there was a little gas coming out of vacuum tube (on the front base of carb)
    that I use for a vacuum gauge in the car. So maybe a bowl level issue? will keep
    disassembling carb.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    Re: Something weird going on
    « Reply #4 on: August 20, 2016 - 03:14:08 AM »
    Looks like  transition slot on primaries is barely open at all, maybe .02 inches.
    Dave Vizards Carb book says should be around .05 or .06 inches.
    Secondaries have no slot visable. Guess I should open that up too.
    On a race engine, or big cam car, he says idle around 1000 to 1200 in gear.
    Will look into all this more tomorrow.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    Re: Something weird going on
    « Reply #5 on: August 20, 2016 - 03:14:32 PM »
    OK, bad primariy power valve. Leaking a little. So that's one item.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    • Posts: 8024
    Re: Something weird going on
    « Reply #6 on: August 20, 2016 - 04:34:47 PM »
    The leaking power valve would explain why I have been getting almost an explosion
    on the right side of the engine, when starting.  A big bang that jolts the engine, making
    me think I had a broken motor mount.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline Chryco Psycho

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    • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
    Re: Something weird going on
    « Reply #7 on: August 20, 2016 - 09:49:47 PM »
    Well the Pv was on the list of possibilities
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    Challenger - You`ll wish You Hadn`t

    Offline cudabob496

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    Re: Something weird going on
    « Reply #8 on: August 25, 2016 - 03:49:32 PM »
    Cwap, new powervalve in, but running rougher and richer, about 11 on the AFR meter.
    Only other thing I did was turn that screw to expose some of the secondary transfer slots,
    which were completely covered by the throttle blades. Guess I'll put those back the way they
    were, and see what happens.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    • Posts: 8024
    Re: Something weird going on
    « Reply #9 on: August 26, 2016 - 03:25:03 AM »
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    Re: Something weird going on
    « Reply #10 on: August 26, 2016 - 02:55:35 PM »
    still no luck
    since carb is 16 years old, can't hurt to replace metering blocks.
    Only about $60 a piece.
    gonna replace throttle plate gasket as well.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline Cudakiller70

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    Re: Something weird going on
    « Reply #11 on: August 26, 2016 - 05:43:03 PM »
    At this point would it be best to do a complete rebuild  :dunno:
    Wish I could help you, but I just don't know.
    Logged
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    Offline cudabob496

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    Re: Something weird going on
    « Reply #12 on: August 26, 2016 - 09:43:12 PM »
    Quote from: Cudakiller70 on August 26, 2016 - 05:43:03 PM
    At this point would it be best to do a complete rebuild  :dunno:
    Wish I could help you, but I just don't know.

    Ya, basically already have, with new gaskets, except the throttle plate gasket. Also vacuumed
    out all the metering block and air bleed passages.
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline cudabob496

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    Re: Something weird going on
    « Reply #13 on: August 26, 2016 - 10:19:06 PM »
    ok, have noticed the last two times I drain the bowls, the front primary bowl
    only has about 25% gas, compared to the secondary bowl.

    there is guidance for when you turn the bowl upside down, and look at the float,
    and determine if it is in the proper position, like the top of float just is in line with the two
    brass scres behind it?
    « Last Edit: August 26, 2016 - 10:27:06 PM by cudabob496 »
    Logged
    72 Cuda, owned 25 years. 496, with ported Stage VI heads, .625 in solid roller, 254/258 at .050, 3500 stall, 3.91 rear. 850 Holley DP, Reverse manual valve body.

    1999 Trans Am, LS1, heads, cam, headers, stall, etc! Love to surprise the rice rockets with this one. They seem so confident, then it's "what the heck just happened?"

    2011 Kawasaki Z1000

    Offline Chryco Psycho

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    • Posts: 36620
    • 70 Challenger R/T SE 70 tube Chassis Cuda now sold
    Re: Something weird going on
    « Reply #14 on: August 26, 2016 - 10:54:35 PM »
    Approx 2/3 of the float would be submerged & even with the bottom of the sight plug
    is the inlet restricted ?
    Logged

    Challenger - You`ll wish You Hadn`t
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