my 1979 Cadillac Eldorado biarritz

Question by cadillaccryer Reward: 25 Pond Points + 10 Knowledge Tokens Status: Pending a resolution
my 1979 Cadillac Eduardo Biarritz has been stood for some time on restarting it
there is a horrible knocking or coughing back? noise seems to come from the carb, with the engine running if i remove the number one spark plug lead the noise goes away and the engine speeds up and runs smoother?
i thing it is a Cadillac 468 cu in not sure! Distributor is at the front of the engine



Reply from shdwkpr619 User Rating:  100 Knowledge Tokens
Sounds like a broke piston and maybe bent or stuck intake valve. Heres why. A broke piston will knock every time that cylinder fires. Pulling the spark plug wire kills the fire to that cylinder and the knock goes away. Also if a peice of the piston got stuck in the intake valve, every time the cylinder fires it back fires up through the carburator. When you pull the plug wire and kill the fire, it no longer fires back up through the carb, but may just blow air back. The fire coming back up the intake is burning some of the fuel in the intake, thats why when you kill the fire to that cylinder the engine speeds up, because now its getting more fuel.
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Comment from Anonymous
Thanks for the info, the problem was a bent pushrod now runs like a cadillac should, (Smooth)


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