[Rightytighty]

Bought a well used 1991 Chevy P/U. In the process of rehab and engine started billowing blue white smoke...burning oil....figured probably popped a ring or something....did a compression test and found all cylinders to be above the 150psi spec. pulled a valve cover and oil came poring out...found the oil return holes to be plugged with sludge...it is not cooked on like it was overheated...just mushy sludge...my question is: what is the best way to try and clean the engine out and get rid of the sludge????

[KULTULZ]

The best way is to disassemble the engine.

What you might try to do is find some old rifle brushes and chase the drains in the heads. You could possibly drain the oil, leave the drain plug off and clean the top end with varsol (allowing the trash to drain into a catch pan). Put fresh oil in (with a can of cleaner or seafoam), run and redrain, refill and pray the oil screen doesn't become plugged. It is best to do this with a quality mechanical gauge.

Does the oil seem to contain coolant?

[DoubleVision]

This problem is common with these engines, my 4.3 was gummed up as was many others I`ve torn down. After I cleaned mine out with sea foam and carb cleaner, I went to a 180 T stat and the problem hasn`t resurfaced. Due the EGR the manifold runs alot hotter than it did on small blocks of old. while there`s been arguements on rather or not hot or cold causes it, The carbed small blocks with egr didn`t seem to have this problem, the TBI engines run leaner than a carb does which adds more heat. As for cleaning, I would just follow the suggestion already given. Maybe drain the oil, pull the intake if need be and go at it, then remove the oil pan and clean it out as well as the bottom end and it should be okay.

[Countilaw]

This is only my opinion, but I think the brand of oil being used also contributes to the formation of sludge. Some north eastern oils have a lot of paraffin in their oils.

I rebuilt an engine that I had been using Quaker State in. I found a undue amount of sludge in the valley, heads and pan. I rebuilt that engine and started using Castrol. I sold the car and told the new owner that I rebuilt the engine and to use only Castrol.

Several years later, the new owner came back and wanted to rebuild the engine because he had been talking to a guy that had a 383 stroker and he wanted one.

When I took the engine apart, it still looked new inside. I told the owner that it would be a shame to waste the engine. I talked him into a 427 build that I got from a junk yard.

He later came back and said that he was glad that he went with the 427 because now his engine was better than his friend's.

I now use full synthetics in all my engines.

[Rightytighty]

Thank You Very Much for the info on this problem. I have some good ideas from all of it on what to do. I like the transmission fluid idea and may go that route!!!

Will post back when completed and the results I get!!

[MAUSS]

Some north eastern oils have a lot of paraffin in their oils.

No such thing as a "northeastern oil" anymore. Old wives tale from the 50's.