Originally Posted by Tony miller
I have a sbc 350 it smokes at idle and leak oil out the breather filler and PCs valve I also have a rattle when Iím on the gas petal obove 45 mile an hour can someone help me
Not a good sign, this can be from serious but fixable to a rebuild or replacement.
Given that it has high blow by and is speed limited with rattle which might be detonation or an indication of bearing failure which you would see on an oil pressure gauge if it has one.
But your description seems to fit a cam drive failure taking the ignition timing with it since that drives off the cam. Typical here is the timing set is worn out this consists of stretch of the chain and or failure of the cam gear teeth which if factory are nylon, noise being a bigger factor in Detroit think than service life.
- Start by checking and resetting the ignition timing to what is correct for that year and model.
- Then with a timing light on number 1 plug wire bring the revs up to 2000-3000 RPM and slam the throttle shut while observing the timing marks if they wander up and down from your setting more than a couple three degrees either way this is a good sign the timing set is worn out. Detonation and/or blow by are common events that come with cam drive near failures. Pressing the cam drive to failure will result in pistons meeting valves, that converts a hundred dollar repair into a thousands of dollar repair or replacement.
For engine rattles you need to figure out whether this is detonation, or bearing, or piston failure. this takes more of a trained ear but in general connecting rod bearing, piston pin, or piston skirt failures make a double knock each with it's own tone which is hard to describe to someone that hasn't hear them. Crank mains make a single and very heavy sound when they are gone. Rod and main bearing failures reduce to eliminate oil pressure so with a gauge you can see that. Piston pin just makes noise in a double rattle, piston skirt also makes a double rattle neither of these affect oil pressure but the piston skirt can affect blow by if it has damaged the ring lands or is so busted it lets the piston rock in the bore which upsets ring seal.