I think they will fit but second gen are also air assisted as I recall.
I just checked. Yes they are air assisted.

This has not been mentioned before when this subject
has come up in the past. THEY WILL NOT WORK unless the
air pump is installed. I don't know anybody that is running the
air pump. Perhaps as a vacuum source for gyro instruments.
As I recall Ed Anderson is running it as a vacuum source
but I don't think he has plumbed it to the oil injectors.

Ed?

Also the second gen used four lines instead of only two like the third gen.
Two of the four injected oil into the intake manifold.

The first gen 12A engine was not air assisted, used two lines
and injected oil into the float bowl.

Paul Lamar

The oil metering injection is not strictly speaking "air assisted." The function of the check
valves and air bleeds is to reduce the vacuum acting on the metering pump at part throttle
conditions. The system works like this: Oil from the metering pump goes though the lines to a
small chamber within the oil metering "nozzle." To get into the engine, the oil must pass through
a small orifice. On the rotor housings, the orifice is already installed in the housing. On the
intake manifold, the orifice is built into the nozzle. (Note that the third gen engines supply oil
only through the rotor housings.) The chamber is vented upstream of the throttle valve via the
check valve. The orifice restricts the vacuum such that the chamber in the nozzle is operating
very close to the pressure that exists upstream of the throttle plates. On a non-turbo car, this
pressure will be very nearly atmospheric pressure. On a turbo, the pressure will be whatever the
pre-throttle boost pressure is.

Why do they do this? Because the oil metering pump and lines are sensitive to vacuum. If you plug
the air supply to the check valves (nozzles), and blip the throttle, you can see the oil get
sucked out of the metering lines when the manifold vacuum gets high. Then, when the engine is
revved again, there is a significant lag time while the metering lines fill with oil again. The
metering pump is not particularly sensitive to boost pressure, it will deliver the same amount of
oil against fairly high outlet pressures.

Another note: If you trace the "vacuum" line from the oil injector check valve/nozzles, it looks
like it goes to the downstream side of the throttle. The fitting for this line is on the side of
the throttle body, and from the outside it looks like it is downstream of the throttle. Inside the
casting, however, the passage is drilled to the upstream side of the throttle.

The check valve prevents the oil from going into the vacuum lines instead of directly into the
engine.

My opinion (carefully chosen word!) is that a failure of the check valve is a relatively soft
failure mode, especially in applications where the manifold pressure does not change very rapidly,
nor go very low (such as coasting downhill in gear).

Jon Lauter
Rotary Power Marine Corporation

 
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