Vacumn Pumps

[Leadfoot]

Just wondering if anyone has had any experience with runnung a vacumn pump on a Big Block chevy on the salt ? I know they are common in drag racing circles but will they work for 5 miles with out hurting the luburcation of internal parts. Plan on running 12-14 lbs vacumn. Any thoughts ? thanks.

[SPARKY]

I run a dry sump---but I have piston squirters & and EDM drilled rods
the squirters help in several ways .

[Leadfoot]

Ok thanks, I should of mentioned that I do have a wet sump right now.

[Koncretekid]

Just for clarification, are you sure you meant 12-14 lbs vacuum? As in 12-14 psi?  That would be around absolute zero, which I don't think is possible.

[Leadfoot]

Your right...I mean Inches of Mercury. 12" to 14".

[jimmy six]

A friend mine runs one on 600" blown BBC with dry sump and has been over 250. I've run one for over 20 years on an inline engine.....What's your concern?

[Speed Limit 1000]

We sometimes use an electric one from a cheby, it works good and not too hard to find a used one

[Stainless1]

We sometimes use an electric one from a cheby, it works good and not too hard to find a used one

Unless we are running one of the motors set up to create vacuum using the exhaust.  Of course we are running a 60.0 inch motor unless we are running our 84.0 inch big block...    only spinning the motor to 13000 last year, no oiling issues.... wet sump as well. 
It does seem to lower the oil pressure a little, but it helps move it through the motor. 
YEMV 

[Koncretekid]

Theoretically, on a closed wet sump oiling system, the static pressure within the crankcase will have no effect on the oil pressure to the bearings and valves.   Your gauge pressure will read lower, because it will be comparing the actual pressure at the pump within the closed system (say 40 psi which is against an internal static pressure of -7 psi) with atmospheric pressure (which your gauge reads as 0) so the gauge might read 33 psi. The same will be true of a dry sump system, as long as it is a closed system.  On my old BSA, the dry sump tank is vented to atmosphere, so I'm a little concerned about the sump pumps ability to pump against the internal vacuum.  But I'm only hoping for about a vacuum of 7-10 inches of water pressure (about 1/4 to 1/3 of a psi) so I'm not too concerned.

[Leadfoot]

Im concerned mostly about the removing of the oil mist which helps lubrucate the wrist pins.

[jimmy six]

Lead...never lost a piston we could blame on that. My pins are a "palm" fit on the rods and I run a scraper on the pan. The catch can should have a petcock to check after every run. We find about a 1/2 teacup of clean water on the first pass of the day. Condensation. We both have vacuum reliefs set at 9"

25 years ago when I started running one I had it spinning to fast and did suck out some oil. Slowed it down another 20% and have had no problems since. Most are built for "squirt" racing and not full throttle for 5 miles. I would never run again without one. Most use a 3 or 4 vane Moroso amd I use an Aero Space Industries. They say a 4 vane is for a big block but our 600+ inch BBC uses a 3 vane because we took it off a SBC and never had a bearing or pin problem with it.

NASCAR runs a lot of vacuum with their drysump pumps. They have valve spring squirters for cooling so they may have piston/pin squirters too...............Good Luck 

[gas pumper]

We run one on the 608 AA/GL. 582 BBC. 14-15 in vac. Works well. No problems with oiling.

Our engine guy says that over 18 In is when you need to worry about wrist pins and crank bearings. The drag race guys that run hi vac use a coating to retain lube, he says.

[Leadfoot]

Ok thanks everyone for the good answers . Gary

[Rex Schimmer]

If you run a "dry sump" system then the engine case pressure does not have any affect on the engine pressure pump operation as it's inlet is from the bottom of the drysump reservoir. IF you have a "wet sump" system, i.e. one oil pump in the pan of the engine that pumps inlet pressure is the pressure in the case plus the height of the oil above the pump inlet. If you reduce the case pressure you will reduce the pump inlet pressure, if the pump inlet conditions are anywhere close to marginal you will cause the pump to cavitate, i.e. the vacuum at the inlet of the pump will cause the intrapped air and desolved air in the oil to become seperated from the oil in the forms of air bubbles and these will then be pumped into the engine lubrication system. Air has no lubrication properties so guess what happens next. Therefore if you have a dry sump engine then a case vacuum pump is a good idea and worth horsepower, if you have a wet sump engine then I suggest you be very careful.

Rex

[Ron Clevenger]

Use the 4 vane pump if your going to purchase one. The 3 vane can shear off the screws due to it's design. 12-14" will get you the largest percent of power available without oiling issues to the pin. Also an external oil pump is a great addition. It allows you to install an isolator between the oil in the pan and the crank. This helps a bunch in reducing the pounding (piston action) of the oil in the pan which aerates it.

The vacuum pump will also allow lighter tension rings, especially the oil ring which is the biggest drag.

Blessings..........Ron C