Quote:
Originally Posted by Christ
They do this with vacuum pumps for race cars... yes, vacuum in the block is a good thing, and it actually provides more than "marginally greater" ring seals.
I'm not entirely sure how much vacuum they use, but you can get belt-driven vacuum pumps from Summit Racing and Jegs for the purpose.
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Run 10"-12" Hg. At levels significantly higher than that you start getting into issues with seals and oil spray patterns, not to mention that you do need some atmosphere to allow your standard oil pump to work.
You can run lighter tension rings if you can
consistently pull 5" or greater. Don't expect an exhaust extraction valve to accomplish this. Your engine may already have light tension rings. Best to check that out on an engine-specific forum with some very sharp techs. Fairly esoteric knowledge.
There are some common electric vacuum pumps that will draw down the engine like this. I think some of the large GMC SUVs used them for brake boosters; large BMW sedans as well. Be sure to use a well designed catch can inline to reduce the presence of oil vapors or neat oil in the pump -- internals probably not designed for that.
I have also been told that some Toyota diesel engines have an alternator with a vacuum pump built in. That would be trick to adapt over.
I would not expect something like this to survive, say, California EPA inspection -- it would fail the visual test immediately if the technician was familiar with the engine or your setup looked too "Home Depot Engineered." Note that the visual inspection does not "care" if the vehicle has the same or better emissions. There is a formal procedure for getting something like this approved.