It took me a little while to figure out why the plywood mocking brackets in a previous post didn’t fit the A/C compressor properly. CAD mistake? Error exporting the file? Laser cutting error? Nope, nope and nope. If you look at the dimensioned drawing below, you’ll note that the distance between the two mounting points is 5.787”. I assumed that the shaft would be located midway between those points, but if you look closely you’ll note that the left mounting point is further from the shaft. Vintage Air should have split that dimension into two to make the nuance clear and not require someone to figure out what the dimensions are! If anyone else is making a bracket, the left dimension is 3.030” and the right is 2.757”.
Misleading dimensioned drawing of the A/C compressor (left) and version 1.1 of the front accessory plate (right)
After installing the engine with the plywood brackets I realized that I needed to tweak the orientation of compressor. I had oriented its ports horizontally so that they pointed directly at the tubes in the side pods. After mocking the flex lines I realized that they would be straight and wouldn’t have slack to actually flex. So I rotated the compressor 10 degrees counterclockwise (red line in image above) to create a slight arc and some slack in the lines.
The next step was to finalize the amount of space between the front and rear mounting plates which had been cut from 1/4” mild steel. The A/C compressor has a clutch that’s integrated into the pulley which means that you can’t just swap or shim the pulley to align it. So in terms of front-to-back alignment, it has to go where it wants to go. I bolted the compressor to the front mounting plate and aligned its pully with the accessory drive pulley. This determined that the front plate needed to be 3.650” in front of the rear plate. Now that the distance was set between the front and rear plates I looked for aluminum spacers that I could trim to size for the M10 screws that go into the block. I wasn’t able to find any that were long enough, so I fabricated five of them from 20 mm 6061 rod.
The required through hole is fairly deep. When hole depth reaches 4x hole diameter, you should “peck” drill. It’s a simple process where you drill a little ways into the material (the peck distance), withdraw some distance to evacuate the chips from the bore, and then plunge again to take another peck. The motion is not dissimilar to a woodpecker. When the depth exceeds 8x the diameter you want to use a parabolic-flute drill bit. Parabolic flutes have a flute geometry with a faster/wider spiral that improves chip extraction vs. a standard twist drill. So I ordered a10mm parabolic drill bit from McMaster.
I used my lathe to cut, face and drill the rod. I withdrew the bit all of the way on each peck and used a brush to clear the chips from the spiral and to apply some cutting fluid.
The compressor’s rear tabs have flanged steel bushings that hit the rear plate so I knocked them out with a hammer and punch. This left a gap between the mounting tabs and the rear plate. After measuring the gap I realized that it was only 0.020” more than the flange on the bushing. So I ordered 0.020” stainless steel shims from McMaster. I then slipped the shims over the bushings and knocked them all of the way in. This is a perfect solution because the sleeves capture the shims — the last thing that I need are two more small things to lose.
Not so fast. When I tapped the bushings all of the way they protruded past the other side of the mounting tabs which prevented the nylocs from binding on the mounting tabs. So I knocked the bushings out again, trimmed them and knocked them in again.
Modified bushing (left), stock bushing (right) and stainless steel shims (top)
A/C compressor installed between the front and rear mounting plates. The brushed cylinder is one of the custom spacers that I fabricated on the lathe. If you look closely at the rear mounting tab with a “C” on it, you’ll see the shim and the bushing’s flange pinched between it and the rear plate.
As far as I can tell, the compressor pulley is within 2-3 thousands of the drive pulley. Next up is the alternator, the automatic tensioner and another version of the mounting plates.