ArKay99

iTrader: (1)

I've read about using a vaccum pump to create higher than normal cranckcase vacuum to seal the rings better and give better performance. I've also read that too much can ruin your main bearings.
I'm assuming that the vacuum draws the oil out of the bearings before it can be replenished but I would think the the oil would see the difference and more would flow into the bearing because of the pressure differential. I.E. if I had 50psi at the pump and -8lbs. in the cranckcase, the oil would see a pressure differential of 58psi and that much pressure would be applied to the bearings.

Eddiep

iTrader: (26)

Differential shouldn't change ... Don't forget that the oil pump is drawing from a source that has a vacuum above it

[Edit]

NM ... Just thought about this some more. We might have to take into account the total area of the pump inlet is versus the total area of the oil's outlet from the bearings/rockers to know the overal effect of a crank case vacuum??? I *think* that if the inlet area > outlet area, a vacuum will hurt the pump output capacity.

Not sure about this, but my head is starting to hurt so I'm not going to think about this any more.

felton316

http://www.competitionplus.com/09_17...oroso_pump.htm

They state the negative pressure allows for less oil pressure but high volume, which helps reduce temps, which is a good thing.

Armageddon

iTrader: (41)

I guess if the vacuum was strong enough it could break the hydrodynamic flow of the oil. Something else is vacuum brings down boiling points... a shitload of vacuum could also effect how oil reacts to heat.

Old Geezer

iTrader: (3)

The first place the problem with too much crankcase vac will likely show up, is on the wrist pins/bores....

ArKay99

iTrader: (1)

That is one of the things I would like to understand. Why?

Old Geezer

iTrader: (3)

The vac is pulling a large amt of the oil off of the cyl walls. The wrist pins get some of their oil from feed holes behind the rings, and splash on the bottom side of the piston. Removing a large portion of that oil, will reduce the oiling to the pins/bores.

ArKay99

iTrader: (1)

I'm not trying to be contrary or obstinate, but I don't understand how vacuum could pull oil off the walls of the cylinder under the rings. I'll take you word for it that it happens, but what is the mechanism for putting the oil onto the walls, and how does vacuum affect that? I would think that lower pressure may contribute to less turbulence in the crankcase, is that one factor?

Wnts2Go10O

iTrader: (12)

the way i understand vaccum is that it wont nessecarily pull oil off but create an enviroment where the oil becomes thinner because of that vaccum. why would it be thinner? it would be thinner because the vaccum would give the oil room to expand. the higher volume explained earlier would be void then. you arent really adding volume, youre jus moving oil that has its molecules farther apart. i guess that the reason why the walls/rings would lose oil would be from A) the lower boiling/burning point and B) from it being thinned by the vaccum

DAPSUPRSLO

iTrader: (14)

Guys, here's my understanding of the whole situation from someone who fixes others mistakes all the time. The problem with the vacuum pump is that it takes away from the posative pressure in the crank case which aids the pick up side of the oil pump. The oil pump does create somewhat of a pressure drop in which the higher pressure oil contained in the oil pan must flow through; however, the oil pump by itself cannot creat so much of a pressure drop that it by itself can suck the oil up to the pick up of the pump. In other words the oil pump relies on some posative pressure in the oil pan (caused by blow by) to aid in forcing oil up to the pick up side of the pump, put too much negative pressure in the oil pan via a vacuum pump, and the pick up side of the oil pump cannot keep up and draw the oil into it.

You can run a vacuum pump, but there is a fine line of too much vacuum in the oil pan. I don't know what that line is but i'm sure many do. Good luck!

DAPSUPRSLO

iTrader: (14)

https://ls1tech.com/forums/showthrea...8&page=3&pp=20

Look at reply 46 for further explanation!

ArKay99

iTrader: (1)

That explains it. The oil is part of the vacuum system. Now I see why a vacuum pump would be desireable in a dry sump and not so much so in a wet sump.

1fastWS6

iTrader: (3)

Up to 15" of vacuum is considered 'safe' for a wet sump engine. Dry sump guys run 20-25". I have mine setup to pull 10".

Lethal Injection

Did you do testing to see the difference in times before and after the pump to see the improvement?

1fastWS6

iTrader: (3)

No, not really. You really need low tension rings to take full advantage of a vac. system as far as increasing HP, which I don't have. But my header evac wasn't working worth a **** and I'll have low tension rings after the next rebuild. Even if it did add 10-15 hp I wouldn't hardly notice it on this engine since it can lose twice that between runs if the temp/humidity changes a little.