[mitchc]

I have a cylinder on my 383 that is fauling the plug. I've ran a compression test and a cylinder leak down test and I have 160 psi compression and I am holding 100% in the leak down test. This motor does not have more than 5000 mile on it. All the other cylinders are buring clean but #6. When you are on it hard and back off the throttle it will put out a puff of blue smoke. I just pull the spring and the valve seal (positive type) and it looks fine. I put a bore scope down the spark plug hole and the top of the piston is black from oil. I've always thought if it was rings the outer edge of the piston would be clean but the center would be black. And if its a valve seal or guide the center would be clean and the outer would be black. Well as far as I can see with the bore scope the whole piston is black. I chacked the valve guide (Dart Pro Alum 200 cc heads) were great.

This plug is not wet the black is hard and shinny.. you can not wipe it off.

Any ideal??? http://

[cobalt327]

It sounds like you may have an intake manifold gasket that's allowing oil to be pulled into that intake port from the lifter valley.

Another thing is if the PCV is plumbed into that port of the intake instead of to the carb where the blow by is "shared" by the whole engine.

A diagnostic vacuum gage (undamped needle) may show a vacuum leak- I'd test it to see what you can see.

[DoubleVision]

I agree with Cobalt, check the intake gaskets.