I've got a '73 Impala with a 350 V8. I pulled the top off the motor to replace the valve cover gaskets and to swap the manifold for a 4bbl carb instead of the stock 2bbl. When I got the valve covers off I noticed a good amount of sludge. Not awful, but a nice buildup at the oil drain holes. When I pulled the manifold off I found more sludge in the block.

So now the question is what do I do about it. I was thinking I'd drain the oil, and leave the plug out with a pan under it. I'd physically remove as much of it as I can, and then wash the rest of the exposed parts off with gas and a brush. Then when I put the motor back together I'd run some sludge cleaner through it. Does that sound like a plan or should I take a different route?

I guess if it is simple enough I could also pull the pan, but I have never taken the pan off a Chevy. I remember on my old man's Ford he had to jack the engine off the mounts, and that's more work that I want to do right now. Perhaps I should peruse the shop manual to see how much trouble that would be...

 

In your Impala your just about going to have to remove the engine to remove the oil pan. The cross frame will stop you and the exhaust Y pipe will definately stop you.
I would use diesel fuel or kerosene to brush out the crud and leave the drain plug out as you do it. Also I am NOT big on running additives through to clean up the motors insides mainly because believe it or not the "crud" actually is helping your old piston rings and the seals in your engine to keep from leaking past.
One more thing to think about is the timing chain and gears. How long has it been since they have been replaced? In order to replace the chain your going to have to drop the oil pan unless you know a mechanic that knows the trickto getting the timing cover back on without dropping it.

 

Yea, that's what I thought. I'm not going to muck with the pan now. Up until Saturday, the motor was totally stock, except for parts replaced at tuneups. If I have to drop the pan or replace the timing chain I'll probably just pull the whole motor and go all out. It's something I'd like to do, just not now.

I will think about your comment on the sludge helping the seals, but I'm going to go ahead and clean the exposed parts (rockers, valve springs, lifters, top of the block) with solvent and a brush while I have the top off.

 

I have no problem with a little brush action cleaning of exposed parts its the engine flush in a can crap I don't think is wise to do. If your thinking about major surgery on the motor in the future don't forget the cam bearings. They have a whole lot more to do with oil pressure than you think.