I have not actually operated a Sigma-Tec AEON pump, as it will not fit in my Sierra. The combination of the engine mount tubes, the IO360-A1B6, and the large Bendix 1200-series magnetos leaves too little space for the AEON, regardless of its orientation. It may, however, fit in some installations.

What follows is a series of dimensional descriptions by fellow BAC member Dave Cunningham. When coupled with the photos on BAC under Photo Gallery/Maintenance Photos, you may be able to judge where you can use the AEON in your application.

The AEON is certainly a much improved design over the conventional carbon-vane pump, in many respects, and should have a much longer reliable life. The warranty on it is 2,000 hours and five years, and unlike the traditional pumps, it is fully repairable. Dave Cunningham, pump photos: I just took four dimensions down that might be useful. The first is the height of the pump chamber cover (the black part; everything above the hogged-out aluminum piece); I came up with 1.875 inches (1 7/8″). The second is the distance from the centerline of the splined shaft to the top of the pump chamber cover; 3.75 inches (3 3/4″). The third is the width of the piston pump main body at the widest part of the top; 3.125 inches (3 1/8″). The fourth is the depth of the pump, which I think of as the distance from the mounting flange (which makes contact with the mounting gasket), to the aft-most part of the pump (where the ports are); 4.062 inches (4 1/16″).

Here is a verbal outline of the photos: One lines up the splined shafts reasonably close (less than a tenth of an inch offset, I’d guess). One shows the small difference in width between the new and old style pumps; no attempt made to line up anything. They’re both just laying there. One lines up the splined shafts, with the shafts out of frame. It gives you some sense of the difference in height; but more importantly, it illustrates the amount of mass in the upper right quadrant of the AEON pump. This is what most installations will have problems with.

Two photos are very similar; just taken from slightly different positions. If you speak Photoshop, you could cut one image and superimpose a transparency of it over the remaining one, to simulate a cutout. Scale it appropriately for your printer, print it out, and you’d have a template of sorts. One butts one splined shaft up against the other. The scale allows one to approximate how far up and out (or over and out, depending on the orientation) the pump would go. As you can see, the bottom isn’t an issue; it has the same clearance as the RAPCO. Even the depth, from mounting flange to the ports, isn’t a big deal; it’s the manifold and piston/cylinder assembly on top, that are the interference culprits. Three photos place the pumps one on top of the other, lining up the mounting flanges. There are three different positions, for perspective. And finally, two photos show the pumps placed one on top of the other, with the splined shafts lined up axially. This gives you some sense of what you would accomplish if you could overlay transparencies.

Dave Cunningham, installation area photos: One is taken from the right side of the plane, showing how the vacuum pump mounting pad lines up with the tubular engine mount frame. You can tell that the plane of the mounting pad surface is well forward of the main (curved) piece of steel tubing that runs above and around the vacuum pump mounting pad. One is from slightly right of directly overhead, showing the same layout, but also beginning to show that, at least in my installation, the fuel distributor pressure gauge line penetrates the baffle directly over the mounting pad. One is taken from right of overhead in the plane of the mounting pad surface, showing the alignment of the mounting pad surface and the engine mount frame. Bad interference area. One is taken from far left of overhead in the plane of the mounting pad surface, showing the alignment of the mounting pad surface and the engine mount frame. Still bad. One can also see the relative placement of the fuel line. I suspect that with a little effort that could be moved, but it’s not the most severe problem. One is a general shot, intended to illustrate the proximity of the plate on which the actual (rubber) engine vibration isolator mounts, relative to the vacuum pump mounting pad. One shows one of two conceivable mounting orientations, this one rotated 90 degrees right as viewed from the cabin. Although you can’t tell it from this picture, the pump mounting holes are pretty closely lined up with the studs (I’d guesstimate they are no more than 0.25 inches low, likely less).

The pump is as far forward as it will go, with the socket head cap screw (the right-most one in this picture) being hard up against the place in the mount where the diagonal brace is welded into the main frame. In this orientation, there is no possibility that the pump can be moved forward the required one inch plus; it won’t clear the frame tube nor will it get past the absorber mounting plate. One is another shot of the same placement, but from just right of overhead. One is another shot of the same placement, but from the left, showing the contact with the frame at the aforementioned weldment. One is another shot of the same placement, but from very nearly overhead, again showing interference with the engine mount. One shows the other conceivable mounting orientation, vertical as viewed from the cabin. As you can tell from this picture, the pump mounting holes are three quarters to one inch below the mounting studs and the pump would need to be moved another inch and a quarter or so forward. You can see the height problem, with the top of the pump clearly being too high for the engine mount. One illustrates the previous point from the perspective of the pump mounting flange. The pump still needs to be moved as outlined above, but the top of the frame would pretty clearly prevent that.

Submitted by Mike Rellihan


Thank you for adding to the resources available for your Fellow BAC Members.