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extreme bucking


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ive tried everything but i still get bucking when more than half throttle. I had replaced my ignition cap and rotor, wires, plugs, coil... i dont think it could be vapor lock or anything fuel related because when the car starts to buck, the tachometer goes up and down all over the place.

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Something similar has happend to me and it was a worn out dizzy. Remove cap and lift the the rotor up and down and all around, see if there is any paly in the dizzy. I would also check the advance, springs, weights etc. Do not know what you have just some ideas.

 

Also have seen a bad ground do symptons similar.

 

John

 

ive tried everything but i still get bucking when more than half throttle. I had replaced my ignition cap and rotor, wires, plugs, coil... i dont think it could be vapor lock or anything fuel related because when the car starts to buck, the tachometer goes up and down all over the place.
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check your timing. How much total advance are you running?

 

im running 34 degrees total timing on 91 pump

 

If it happens at a certain load I would look at fuel, too lean.

 

it happens full throttle, and part throttle @ highway speeds. Im pretty sure its the distributor because during grid lock traffic today the tachometer was going crazy just sitting on idle. This would be the 3rd distributor replaced this year which is getting rediculous.

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You could also get the same symptoms if you have broken piston lands, which is the sapce between the two compression rings and the oil rings. To check this do a compression check to be sure. You should also see puffing from the oil fill cap when its removed.

 

but that wouldnt explain the erratic tachometer... im looking to lock my distributor with some jb weld or epoxy... i know theres a thread about it but i will try to take as many pictures of the process as possible because that thread is hard to follow without pictures.

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Actually when a piston land fractures, well enough of them, it actually causes not only blow by but in extreme cases will try and stop the motion of the pistons by allowing the explosion to expand past the pistons and into the crank case. This could and in my case did cause extreme bucking. Granted I fractured 5 piston lands out of the 6 and was running over 30lbs of boost to turbo pistons. The tach did jump all over the placeduring bucking. I limped the car to a place to work on it which still bucked whenever I tried to put a load on the car more than a real old granny drive. Another thing that could cause an issue with the tach is a part in the distributor, we used to call the stator. It looks like a ring with a star on it. Check the teeth on this and make sure the gap is correct and use a brass feeler gauge not the ones containing metal. If it can be magnitized then it should not be used to check the gap. Hope this helps.

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