View Full Version : Oil and Vacuum Pump (original & rare)

11-07-2011, 03:09 PM
Howard Prout has a good spare, and I had never seen one before my visit to his house in Canada. I don't think this part can be purchased any more. Howard said Cadillac is the only other car he knows of that also used a oil/vacuum pump.

Here is the 430 original pump:
Howard fabricated the top flange and tube piece so he could run the pump in a bucket of oil.

The flared pipe (on the right) pulls vacuum in, and the short vertical pipe exhausts air above the oil level inside the pan.

Here is the oil pickup and vacuum tube.


I was surprised to see, "AC" on the bottom of the pump. This isn't the first part I have seen Ford purchase from GM. BTW, do you know that AC stands for Albert Champion? Yep, same guy. - Dave

Howard Prout
11-07-2011, 07:53 PM
This system wasn't one of Ford's better ideas. These pumps are small scale vane pumps. There is a rotor on an eccentric cam. The rotor has two slots in it for the vanes. As the vanes rotate in the active cycle, they reduce the volume of fluid in the cell, the resulting increasing pressure causes the fluid to come under more pressure, and as it tries to escape through the vent,a vacuum is created.

The amount of vacuum created is a function of three things, the fit of the vanes to the housing, the rotational velocity of the rotor and the viscosity of the oil - remember this thing is running submerged in oil! The vanes have to seal against not just against the wall of the housing, but the top and bottom surfaces as well. I was able to achieve a tolerance of no more than 0.001" to all surfaces. In theory, the faster the rotor turns, the more opportunity per time unit to create vacuum. In reality, the system maxs out at about 2000 rpm. The viscosity of the oil is a critical factor. When the engine oil is cold, it is thicker and creates a better seal between the vanes and the housing. As the oil gets hotter and less viscous, its ability to maintain the seal drops.

The vacuum pump currently in my engine produces about 27" Hg at fast idle - say 1000 rpm- when it us cold which is pretty darn good. But when the oil gets fully warmed up, it will only produce about 12" Hg at 2000 rpm - not enough to operate the vacuum windshield wipers.

One of the things you have to be careful about is to not let the sources of vacuum cross over. The volume of air produced by the vacuum pump will never be enough to change the vacuum in the intake manifold but you certainly don't want manifold vacuum getting into the crankcase, so some one way valves are required to make sure that any vacuum required comes from the source of greatest vacuum. I have two vacuum gauges mounted on the lower side of my dash - one for each source of vacuum so I can tell at a glance what the current situation is.

Dave loaded a number of pictures of the exterior of the vacuum/oil pump combo. The picture I attached is a combo showing the vacuum pump in various stages of assembly.

04-14-2012, 03:34 PM
I was returning to western Iowa from Rantoul AFB, Illinois one January nite in 1965. Driving my dad's 1958 Merc with a 383 modified. I was running never under 100MPH for an hour , then slowed to 85 MPH the rest of the 600 miles. Made it home OK. The next morning I started the Merc, no oil pressure! Found out the vacuum pump seized-up after shut it off the nite before. Did away with the vacuum pump, (installed a standard pump), wipers still worked good.

04-16-2012, 11:26 AM
The reason this type of vacuum pump was used on the MEL engine was that the regular dual action (fuel pressure and vacuum source) fuel pump that was used on the FE, Y and six cylinders of the period was the placement of the fuel pump on the MEL. If a dual action pump was used, the hood could not be closed.

The prototype MEL was fitted with the FE fuel pump location. Why engineers would place it where it finally wound up is anyone's guess. It is right in the middle of a hot air zone.