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1972 Corvette Scarlett Project Car - Vintage Air Gen 4 Underhood Components

No Sweat - Part 1: Installing the underhood components of Vintage Air’s Gen 4 system

Jeremy Clough Oct 13, 2014
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Those who have been following Scarlett, our '72 coupe project car, may recall the ill-starred road trip we took in her to the Georgia coast in search of barbecue. After driving several hundred miles on backroads, at the very height of a brutal southern summer, we told the story as The Pig Tour (Dec. '12), which should have amply conveyed the misery resulting from the car's lack of functional air conditioning. In the end, we found our barbecue, and it was us. After that experience there was no question Scarlett would get new air conditioning, and there was similarly little question that we would use Vintage Air for our retrofit.

Well-known for their high-performance air-conditioning systems, Vintage Air offers everything from their universal-fit Gen II system, which can be installed in virtually any car with room for a condenser, adequate airflow, and an engine that can drive a compressor, up to their sophisticated Gen IV system, which is what we installed. Available in either an evaporator kit, or the complete kit we ordered, the SureFit Gen IV system completely eliminates the problematic cable-and-vacuum operating system of the factory air conditioning, replacing it with a fully electronic control system. For those who, like me, want to keep factory-appearing controls, the system still uses the factory control panel, with only fairly simple internal modifications.

There are two important stages in installing the kit: the physical components that have to be installed to actually create the cold air, most of which go under the hood, and the parts that go under the dash (including the wiring, controls, and vents) and get the cold air into the passenger compartment. We'll start with the underhood parts in this installment, and follow up with the dash side of things next month.

The installation actually begins during assembly of the front accessory drive on the engine, when the compressor is installed. This was a task we chose to do while the engine was still outside of the car. Since we located the compressor low on the passenger side, in the standard location for an LS-powered Corvette, we had some interference issues with the frame and suspension components, and had to modify them to clear the compressor, as well as weld up custom fittings for the hoses that would bolt to the compressor. For those interested in a slightly less-involved installation, Vintage Air's FrontRunner pulley system will mount the compressor higher, about where we put the alternator.

That'll make the hot air cool. Next month we'll get the cool air into the interior and tell it where to go.


01. We started the Vintage Air installation by bolting the polished compressor into place on the front of our LS3 416. While there are other serpentine systems available that put the compressor in a higher, and frankly easier to deal with, location we used a Street Shop accessory drive that mounted it low in a factory type position. This system also utilized a dedicated drive belt.


02. Part of what we had to do to make the compressor fit, without interference, was to modify the compressor fittings so the hoses could be routed around the front suspension components. While we simply used an extension at the rear, we welded up a tight 90-degree elbow for the front fitting.


03. Here’s the evaporator unit from Vintage Air. When installed, what you see is the top. No doubt, it looks pretty daunting, but a mix of mocking things up with both the dash and engine out of the car, and careful attention to the instructions, made it relatively easy to get it in the car.


04. One of the advances of the Gen IV Vintage Air system is the upgraded electronics that are used to control the system, including these stepper motors. The factory box used a vacuum system for these controls, with all of those attendant difficulties.


05. Because Scarlett was a factory air car, we didn’t have to cut the oval holes near the top of the radiator core support part of the fenderwell that the hard lines pass through as they go to and from the front-mounted condenser, which are shown here in the upper right part of the photo, and with the core support removed. Non-air cars will need to use the included template to do a little sawzall surgery here.


06. Before the evaporator can be installed, it first has to be assembled, starting with the hard lines that will go from the box through the firewall, and which require O-rings that should be lubricated prior to assembly. Once bolted securely in place, the larger suction line will need to be insulated: the yellow-capped lines are the heater lines.


07. The mounting brackets also have to be bolted into place on the evaporator. There’s one on the back of the box that mounts to the firewall and one that goes on the front and screws into the birdcage. I found the instructions a little vague on this part, and installed them incorrectly the first time, but fixed the problem when the box wouldn’t mount properly.


08. You’ll need to drill additional holes around the firewall opening prior to mounting the box. While we had the luxury of drilling these from the engine compartment, since the engine was out when we did it, the template is oriented for use from beneath the dash.


09. The evaporator in place and screwed to the birdcage with a pair of sheetmetal screws. There’s a piece of clear plastic included with the kit that’s supposed to be attached to the top of the box: we used a few dabs of black RTV to hold it in place. The ducting will later attach to the plenum on the left side of the box, and the controller will plug in through the rectangular cutout in the mounting bracket. You’ll also need to drill a drain hole in the floorboard/firewall area and connect it to the box.


10. With the box installed under the dash, the four hardlines protrude through the firewall into the engine compartment. Sealing that up is the next priority. The heater hoses are capped in yellow, and use the familiar nipple and hose clamp arrangement, while the blue-capped hard lines are AN.


11. The fresh-air vent inside the car will need to be sealed in two places: on the firewall and the inside vent near the kick panel. We used the supplied block off cap, and sealed it up with black RTV. It helps to be able to reach this from the rear, so it’s wise to install this before the box, and before the interior block off.


12. To cap off the inside part of the fresh-air vent, you’ll first remove the vacuum-controlled door assembly (and in our case finding a long-lost wrench inside and getting a spider bite) and then install the foam-sealed plastic cap that comes with the kit. Secure it in place with a pair of sheetmetal screws, which is a little bit of a trick in the confined space you’ll be working in.


13. Before we installed the firewall cover, we insulated it with a combination heat/sound deadener, which was carefully cut to shape. With the stout LS3 and sidepipes, the car is going be somewhat unavoidably loud, so there’s no sense in not doing what we can to make it manageable.


14. The firewall with both the cap and firewall cover installed. As with the fresh-air cap, we sealed the firewall cover in place with black RTV. There’s another firewall cap yet to come that will go around the hard lines, sealing them with rubber grommets.


15. We ran the heater hoses, which attach with a hose clamp, when we assembled the engine cooling system. Once all the A/C components are in place, however, you’ll need to assemble the AN-style coolant lines that go between the evaporator, compressor, and condenser. Once we measured the lines and cut them to length, Seth Wood, of Lucky’s Restorations, used a vice-mounted crimper to crimp the hose ends.


16. And here are the complete hoses. When you’re crimping the hose ends, be aware of which way the ends are oriented. Those with fittings that have a bend at either end will need to be lined up correctly relative to each other before crimping, or it will be difficult or impossible to install the hoses properly on their fittings.


17. The hoses installed at the firewall, with the heater hoses on the left, and the coolant hoses on the right. Note the port on the upper suction line, you’ll want to orient that fitting where you can get to it, otherwise servicing the system is going to be a real pain.


18. The radiator-like condenser attaches to the front of the radiator core support using the same bolts that hold the upper radiator clamps in place. We installed the condenser at the same time we installed our DeWitts radiator.


19. The condenser bolted into place on the core support. Note the upper hard line, which will pass through the oval cuts adjacent to the core support. The lower hard line, which is not visible here, goes to the drier.


20. The drier mounts just in front and to the passenger’s side of the condenser using a simple clamp that’s attached to a stud. While it comes with a binary switch, we replaced that with the optional trinary switch that will let us add an auxiliary set of fans to make sure we get the maximum cooling possible.


Vintage Air
San Antonio, TX 78266
Corvette Central
Sawyer, MI 49125
Street Shop, Inc.
Athens, AL 35611



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