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Discussion Starter #1
I've got a 72 gto im working on with a 400 fourbarrel ( rochester) when at idle the motor shake? It has new motor mounts, trans mount, balancer is tight, it does have a exhaust manifold leak, the points are new. Please help in baffled!~!
 

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Have you gone through all the basics? ...Like pulling one plug wire at a time to see if it is a misfire in one cylinder? Have you adjusted the idle air screws to see if you can smooth it out? There are so many basic places to start, that it's hard to help diagnose without more information and knowing what can be ruled out.

Chuck
 

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This is the classic: "My engine doesn't run right, what's wrong with it?"
Like said above do all the usual engine diagnostic procedures or call the psychic hotline.
 

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Are the heads all stock. Unleaded gasoline is bad for exhaust valves. Have the exhaust valve seats be upgraded to Hardened seats? You could have an exhaust valve seat gone bad and the valve has moved up in the head. Therefore it is out of adjustment. Making the engine shake.

Bryan
 

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Discussion Starter #7
just got in from the car its the wierdest thing, car sounds like it has a nasty exhaust leak, but if i cover up some of the intake of the carb with my hand it the idle shoots up stops shaking and runs a hell of alot smoother? along with the exhaust leak disappearing?? I'm the bad carb???????
 

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Vacuum leak.
 

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I checked all the vacumn lines going to the carb? Do you think it could be the car itself?
 

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I checked all the vacumn lines going to the carb? Do you think it could be the car itself?
There could be a leak around the intake, the base of the carburator, brake booster, vacuum line to the trans...etc.. Its hard to say without being in front of it. Might be best to have a friend that knows what they are doing take a look at it or take it to a mechanic.

-Dan
 

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There could be a leak around the intake, the base of the carburator, brake booster, vacuum line to the trans...etc.. Its hard to say without being in front of it. Might be best to have a friend that knows what they are doing take a look at it or take it to a mechanic.

-Dan
If you suspect a vacuum leak around the carb, you can spray carb cleaner around the flange and vacuum fittings. If you hear a change in your idle you will have found a leak.
 

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If you suspect a vacuum leak around the carb, you can spray carb cleaner around the flange and vacuum fittings. If you hear a change in your idle you will have found a leak.

Be careful with that. Carb cleaner is volatile enough that the vapor can be pulled in through the venturi and change the idle, making you THINK you've found a vacuum leak.
 

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Be careful with that. Carb cleaner is volatile enough that the vapor can be pulled in through the venturi and change the idle, making you THINK you've found a vacuum leak.
I shoud have mentioned to repeat a couple times to assure you aren't getting drift from the vapors .....
 

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um i know this is going to sound stupied but isnt that what a motor does :devil: now im kiddin i would check timinmg and like everyone else said you may have your plugs wires wrong ill bet your points may have something to do with it too :yes:
 

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Also check all the header bolts are tight.
 

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its that nasty cam lope mann!!!! :devil:
 
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