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Old 05-02-2003, 02:28 AM
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Post Problem Returns

A good while back I posted on how my car had 14 psi fuel pressure at idle, and I had narrowed it down to the cam, I changed cams and got a new Demon carb, Put it back together and had no problem, good 5 psi fuel pressure (or so I thought) and it ran great. I drove it for months, I took off the fuel pressure gauge as it stopped working, instead of getting another I just left it off, a few weeks back I noticed my car wouldn`t hold a Idle, everytime I stopped it would flutuate up and down, so I`d get out and adjust the idle mixture, it would start to idle smooth again, days ago I decided to take the bowl off and check the power valve as well as the idle circuits, everything checked out ok so I put it back together and the dreaded problem returned, fuel started pouring out of the boosters, it flooded and went dead. I got another pressure gauge, it checked out to be 12 PSI, so I said screw it and just added a fuel pressure regulator and got another gauge and got it under control, what I don`t get is why did the problem just now return? I`m running a stock mechanical pump with a filter close to the tank, and another after the pump, even so now the problem is under control, the car still won`t hold a idle and it`s driving me nuts, I`ve did as the instruction manual said too many times, reset butterflies, checked fuel pressure, turn out mixture screws, but even so it says to start with a turn and a half out, it won`t idle at all there, it idles best about 3/4 turn out, and it also has a surge at cruise that i can`t seem to get out no matter how I set the idle mixture or floats, years ago I had a problem like this one, and it was due to the intake being warped, so i`m starting to suspect a vacuum leak at the intake, is there anyways to check this? I`ve tried the top side with carb cleaner and made no difference, and my car uses a quart of oil every 2 weeks and shows it on some plugs, my heads were fresh reworked, new guides, seals, and it only has 1700 miles on the engine now. any suggestions would be great before I scrap the whole thing from constantly working on it. thanks much.

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Old 05-02-2003, 06:16 AM
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Pick up one of those wd-40 cans that has a straw and spray along the area where the intake mates to the heads.If there is any change in idle,then you know where the problem is.Is the carb you are using new?Grab a hold fo the throttle shaft and see if you can wiggle it,if there is a change in the idle speed then I would suggest that your shaft shims are pooched and the carb needs a rebuild that includes new ones.
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Old 05-02-2003, 06:28 AM
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Sounds like the bottom side of the intake manifold gasket is leaking between some intake ports and the valley area. No good way to check it, except to take the manifold off. Sorry.
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Old 05-02-2003, 07:52 AM
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It almost sounds like a timing issue. The flooding problem might be totally unrelated. Almost sounds like the vacuum advance is moving the timing around and is doing something to the idle. As far as where the mixture screws are, are the throttle plates drilled out? Are the transfer slots too exposed? Maybe there's not enough vacuum at idle to pull the fuel through the idle cicuit and the throttle plates are too far open. Maybe there's some debris in one of the air bleeds. Just some thoughts.

[ May 02, 2003: Message edited by: engineczar ]</p>
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