Vacuum Pumps
12-17-2002, 08:54 AM
#1
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Vacuum Pumps
Has anyone used a vacuum pump for a crankcase evac. system on a boat? They are worth a few hp's on our drag race motors.
12-17-2002, 06:09 PM
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With the type of clearences a marine engine is set to, and the type of gain you have to have to notice a diference I do not think you'd see any difference to make it worth while on an offshore style boat.
12-17-2002, 06:34 PM
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Vacuum in the crankcase can be a good thing. It helps oil leaks, piston ring seal and many other things. Most of our engines depend on splash oiling to lube the upper rod end, piston skirts, and other parts. To get sufficient splash oiling, you must be careful how much air you remove, too much vacuum and you will scuff pistons and other bad things. I have seen small vacuum numbers on endurance motors help power, oil consumption (expecially with low tension oil rings) and any oil leaks. If you try this, let me know how it works-just proceed with caution!!!
Hope this helps.
Hope this helps.
12-20-2002, 09:50 AM
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Agree with blown1100, in a high hp application you will see a benefit, but just more to maintain in a marine engine. I watched my engine builder dyno a 500" pro stock motor @9400 rpm. On the last pull power fell off by 60HP, initially he thought he'd lost a couple of valve springs. Turned out the vanes of the vacuum pump turned in their notice, had to tear down the engine to get all of the pieces out. It was amazing that the pump was worth 60hp though.
If you ever get the chance to see a 500" Pro stocker dynoed...jump at it, very very impressive. This one was "down" on power, 2 yr old technology, and "only" made 1285HP. Valve springs lasted 2-3 pulls and pulls began @7500 and ended @9800
If you ever get the chance to see a 500" Pro stocker dynoed...jump at it, very very impressive. This one was "down" on power, 2 yr old technology, and "only" made 1285HP. Valve springs lasted 2-3 pulls and pulls began @7500 and ended @9800
Last edited by jdnca1; 12-20-2002 at 09:54 AM.
12-21-2002, 08:52 AM
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I have done extensive testing w/ air pumps vane style (moroso, aero,etc) and also have an electric pump that we just finished with. The vane pumps make power on high compression combos in drag race applications, pulling 14" of vacuum, (seen 18-35 hp) but in lower compression apts. they do pull the oil away from the piston pins. not good in long running engines. however the electric pump pulls 4-7 inchs on lower comp engines and makes 7-12 hp more and 10-18 ft lbs torque. so far have not seen any pin problems in 2 yrs running. the electric pump has one draw back and that is your engine is sealed (no breathers) and if you suck oil into the pump it burns up, and the engine has no way to vent so its possible to push out gaskets.. I have a pressure valve to pop off if this happens but their not cheap... turbo NOS and blower engines make the most crank case presser and benefit the most from air pumps and are worth the exspense of a vane style pump.
12-22-2002, 12:13 AM
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Note: If you use vacuum pumps, you need to use certain selas (such as on the crank & by the dampner...........Just lettin ya know cause somoen I know did an engine with a perterson (I think) pump, and didn't use one on the crank.
Just a word of caution..........It all needs to be sealed up
Just a word of caution..........It all needs to be sealed up
