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I have an engine that has been sitting in my garage for some years, and I'm finally going to get some time to work on it and put it back together. The engine's top end is disassembled, but I did not disassemble it further. The engine, a normally aspirated 3.4 liter 6-cylinder engine from a 2000 Porsche 996, is difficult to reassemble and was running just fine when I removed it, which is why I haven't gone any further. The heads, valves and lifters are now all cleaned up and ready to reassemble, and nothing seems to be wrong with the bottom end.

My question

Should I use assembly lube for the parts I'm reassembling and just not worry about the main bearing and other bottom end parts? Is there some other smart way to make sure that the main bearing is sufficiently lubricated for initial startup after all this time?

1 Answer 1

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As you suggested, absotutely use assembly lube on the parts you've taken apart and cleaned. This will ensure there's no wear there while the parts are waiting on oil pressure to build-up and lubricate the parts. I wouldn't worry about taking anything further apart to pre-lube, but there's a way around this to prevent any harshness to your bottom end.

To ensure there'll be no issues with a dry start up, pull the plugs out of the engine and disable the fuel injection. Squirt a little bit of engine oil in through the spark plug holes to lube the cylinders, then spin the engine over. If everything is hooked up inside the vehicle, you should be able to see when oil pressure buildup occurs. When you see the oil pressure come up, all of the internal parts should have plenty of lube on them. You can spin it over a bit more just to make sure, but don't overheat your starter in the process. When this operation is completed, button it all back up and fire the engine. It should be good to go without the worry of dry bearings getting hammered.

The theory here is, with the spark plugs out, there's very little pressure being exerted upon the bearings. You've removed the compression and power cycles from the equation, so the only thing left to put any pressure on it is the inertial forces from the weight of the piston & rod, plus the drag of the rings in the cylinder. In the grand scheme of things, it is a very light load on the bearings. If the top end has assembly lube on it as you've suggested, there's no worries there.

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