383 suddenly running bad

Reece Stephens

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How tight are your plugs too? A loose plug will give you a exhaust leak sound and cause a bad ground effecting spark reliability! Good Luck
Checked all the plugs, they're tight. Also made sure to check all the plug wires and they're all in good shape
 

Reece Stephens

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IF it sounds like an exhaust leak, where might the sound be coming from? Raw fuel smell with no obvious fuel leaks?

Check to see if you can feel some hot exhaust gases escaping from one or both sides of the center of the intake manifold/cyl head location? As in IF the steel valley pan gasket might have failed in that area? If it might have failed on the bottom side, the exhaust gases will go into the crankcase, which means that removing the oil filler cap might have more flow coming out of it than just normal crankcase smells.

Please advise,
CBODY67
I actually checked my blow by, my car has none. It's a 55k mile engine. The valley pan gasket is new, I replaced it a couple of months ago. I did check for exhaust leaks at the manifold, I used soapy water and I didn't see and bubbling
 

MericaMopar

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I'd check the carb, smell of raw fuel, carb float or needle stuck causing fuel to be pushed out through the vent, watch it running with the air filter off and check for fuel being dumped into the intake. I know you said it is a freshly rebuilt carb...but things happen, bad part, etc.
 

Reece Stephens

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I'd check the carb, smell of raw fuel, carb float or needle stuck causing fuel to be pushed out through the vent, watch it running with the air filter off and check for fuel being dumped into the intake. I know you said it is a freshly rebuilt carb...but things happen, bad part, etc.
Fair enough, could be the carb but it snaps to life when I turn the key. I'm thinking it may be my valve seats or valve seals. It's a pre-smog era motor, so it doesn't have hardened valve seats
 

CBODY67

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Fair enough, could be the carb but it snaps to life when I turn the key. I'm thinking it may be my valve seats or valve seals. It's a pre-smog era motor, so it doesn't have hardened valve seats

Valve seats or valve seals do not "go out" suddenly, but over a period of time. A LONG period of time, like 12k miles or more, so gradual that you won't notice it.
 
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