Cooling, Heating and A/C

The car will be civilized and have both heat and air conditioning (A/C). Cooling systems are deceptively simple, but devilishly complicates as described in this article (which I've read twenty times).

Heater Control Valve (HCV)

I keep stumbling into little things that are different with a mid-engine car and I found another one. In a front engine car, the engine (the heating source) and the heater core are very close to each other. In a mid-engine car, the cockpit is between the two. Since it's important to keep the cockpit cool, the last thing I want to do is pump hot water from the engine, through the passenger side of the car, into the heater core under the dash and then have if flow back unused. To prevent this from happening an electric heater control valve (HCV) is installed in the tail section. However, it has been reported that the LS engine can overheat if you start your engine with the A/C on and you have a heater control valve that simply closes the water pump's heater outlet. In other words, LS engines need a constant loop of coolant flowing through the water pump's heater outlet.

To solve this issue, several other builders have used this heater control valve made by Old Air Products which allows coolant to flow even when the heater is turned off. The business end has four 5/8" hose barbs and a valve. Connected to the valve is a servo which is wired to a separate servo controller which is in turn wired to a potentiometer. This provides continuous adjustment from closed to fully open. There are five wires (two for power and three for the position feedback potentiometer) so it's a closed loop control system.

A quick search on the name on the actuator turned this Voltage Control Actuator from Newbase, a Chinese company. The only moderately useful information on that site is the pin out and that it draws a whopping max 300 mA. There is a dimensioned drawing of the locations of the screws that attach the actuator to the valve. Well, the drawings are wrong... I get that it's hard to translate from Chinese to English, but the dimensions were in millimeters!

I considered controlling the HCV via MoTeC by replacing the potentiometer with a digital potentiometer controlled by an Arduino which would then be interfaced to the MoTeC. It would work, but it's a fair amount of work, introduces a bunch of things that might break and I don't really gain anything... nah, not worth doing.

The HCV is awkwardly shaped and there is no easy way to mount it. While pondering the best way to mount it I noticed that the actuator fit perfectly in a triangular dead space in the 2" x 6" chassis. I then realized that I could remove the three screws and and spacers connecting the actuator to the valve and sandwich an aluminum bracket and replace the spacers with shorter ones... OR I could just print a panel large enough to seal the hole (something that was on my to do list) and mount both the motor controller and wire connector. 

The panel is sandwiched between the valve and actuator, thus replacing the standoffs. It was made large enough to cover the hole and mount the motor controller and a new wire connector. There wasn't a way to mount the motor controller so I simply drilled the cover plate mounting holes all of the way through and used stainless 4-40 screws and nylocs. Since heat rises, I decided to print a heat shield between the heater lines and the motor controller and to put Reflect-a-GOLD (aka TRUMP TAPE) on it. I cut 80% of the harness off and terminated one end into a Deutsch connector. I removed the connector to the actuator, fed the wire through a vinyl grommet and re-terminated it on the back side. Since I couldn't figure out what type crimp connectors were used I carefully cut the old ones out of the harness and soldered them on.

Actuator Connector

Wiring map: [Deutsch connector] : (test harness)

  1. Black (Ground)

  2. Red (Power)

  3. White (Potentiometer)

  4. Blue (Potentiometer)

  5. Green (Potentiometer)

Qty.Part NumberDescriptionUnit Price
1   Custom Onyx 3D-Printed Mounting Plate  
1 OAP50-1555 Heater Control Valve - Electronic $99.50
1 DT04-6-2P Deutsch DT Series Six-Pin Receptical Connector with Solid Contacts $8.00
1 1011-0260-0205 Deutsch Mounting Clip $0.70
1   Vinyl 3/8" Grommet  
1   Piece Reflect-a-GOLD  
3   6-32 Stainless Steel Nylocs (for actuator)  
3   10-24 x 1" Stainless Steel Hex-Drive Rounded-Head Screws (for plate)  
3   10-24 Stainless Steel Washers (for plate)  
2   4-40 Stainless Steel Hex-Drive Rounded-Head Screws (for ECU)  
4   4-40 Stainless Steel Washers (for ECU)  
2   4-40 Stainless Steel Nylocs (for ECU)  


Qty.Part NumberDescriptionUnit Price
1  VPE-2044 20' 5/8"Vibrant Performance Reinforced Silicone Heater Hose $70.05
1  VPE-20455 5' 3/4" Vibrant Performance Reinforced Silicone Heater Hose  $24.75
8 54205K11 9/16" to 1-1/16" Stainless Steel Constant-Tension Clamp  $5.25
  • Our A/C insulation tape is a must have when restoring classic vehicles or replacing auto air conditioning components. For use on Expansion Valves, Heater/ Evaporator Case, Low Side (Cold) Lines.

  • Hoses and Clamps:


Qty. Part Number Description Unit Price Ext. Price
1 n/a Custom Coolant Expansion Tank    
1 CHAOGSXH-0163 Primecooling Black Billet Radiator Cap Large Style

1 n/a Custom Stainless Steel Water Pump Outlet Tube $200.00 $200.00 
8 CBM-10924 1.5" Tube Clamps $14.99 $119.92 
8 TB-175 Stainless Steel T-Bolt Hose Clamp (For Tube with 1.5" Inside Diameter) $6.34  


A/C System


The kit comes with a Sanden SD-7B19 compressor The primary issue is that it only has 6 ribs and I have an 8-rub belt. The SD-709 has 8 ribs, pumps ~30% and is ~30% larger with a much lower MAX RPM. 

Description    SD7B10       SD709    
Gooves 6 8
Max RPM 6,000 9,000
Cubic Inches 9.5 6.1
Pulley Lip Diameter 4.850" 4.567"
Total Length 8.366" 6.921"
Heigh Rear Body 4.724" 4.114"


Sanden PDF ; PDF with lots of compressors  Concept One Pulley Systems


When I went to install the supplied Vintage Air evaporator / heater core I discovered that it was even close to fitting because I had purchased the optional removable side-impact bars. So I spent a lot of time looking for something that would fit. I even went so far as to purchase the plastic mockup from Old Air Products for their Hurricane series which would fit. Despite having three models with the connections in three different places, it was going to be a nightmare, at best, to connect.

So, I decided to cut a big hole in the top of the monocoque. While this won't cause a structural issue so long as I keep the hole well away from the welds, I needed to emotionally get over the fact of cutting a hole in it. There are several advantages to mounting it this way: 

  • The two A/C and two heater connections are significantly easier because they are on the top of the foot box, not inside it.

  • The heater lines are routed outside of rather than within the foot box.


  • Discharge/ High Pressure

    • Purpose of condenser is to cool, so no insulation helps things

    • However, you may want to insulate while in the side pod

  • Liquid Line:

  • Suction Line

    • Insulating the line between the evap and the compressor will NOT make things more efficient. The whole point of the compressor is to raise the refrigerant temperature high enough to lose a significant amount of heat in the condenser. If the suction temperature is lowered because of insulation, the discharge temperature will also be lowered. After the evap you WANT the refrigerant to lost heat to ambient so that what enters the compressor is fully vaporized.


Scott's heat deflector; A couple of builders have used the system: Bob's build and Rumbles build. Will used this evaporator.

1 Restomod Air Elevate Control; Black Housing; Red LEDs    $400.00

Water Pump


Radiator, Fans and SHroud

The supplied radiator is beautifully constructed and has been proven to work in many cars. However, making the following changes has been an area of debate for the radiator and coolant expansion tank (aka, surge tank):

  • Move radiator inlet from the bottom to the top and radiator outlet from top to bottom.

  • Move the raditaor bleed line be moved from high-pressure side to the low pressure side

  • Move radiator bleed and steam lines from the bottom of the expansion tank to the top

  • Shrink the size of the radiator bleed line

  • Improve radiator's isolation from vibration and shock

  • Add a fan shroud

  • Upgrade the fans


Use an appropriate mixture of distilled water and commercial coolant that contains corrosion inhibitors.

Do not use any brass components - especially fittings screwed into the radiator as brass promotes electrolysis in aluminum


C&R Racing 

The fans are high-end SPAL brushless, drop-ins.


Honeycomb Radiator Protector 

Side Pods

The primary plumbing that needs to run through side pods are associated with the cooling, heating and A/C systems. Since the body needs to slide over what's installed in the side pod, the usable width is about 3". The side of the chassis tube is 6" high and the body and tub are ~9.5" high, but I might want to use that space for storage or switches. Here's the primary space planning:

  • -6 (3/8”) Wall 5/32” (0.313” total)=> 0.688”

  • -8 (1/2) Wall 5/32” => 0.813”

  • -10 (5/8”) Wall 5/32” => 0.938”

Left Side

Purpose OD Notes
Radiator Supply 2.0" 1.5" stainless steel pipe with two wraps of 5 mm Space Blanket aerogel is ~1.9", allow 0.1" for outer wrap.
A/C Suction 1.0" #10 rubber A/C line, no futher insulation planned. Compressor is on left side due to dry sump.
A/C Discharge 0.9" #8 rubber A/C line, no futher insulation planned. Compressor is on left side due to dry sump.
Radiator Bleed 0.43" -4 Aeroquip Starlite.
Fire Supression    
Rear Brakes 0.2" 3/16" stainless steel brake line.
Electrical ??? TBD

Right Side

Purpose OD Notes
Radiator Return 2.0" 1.5" OD stainless steel pipe with two wraps of 5 mm Space Blanket aerogel is ~1.9", allow 0.1" for outer wrap.
Heater Supply 0.9" 5/8" rubber heater hose, no futher insulation planned.
Heater Return 0.9" 5/8" rubber heater hose, no futher insulation planned.
Air Jack   -6 AN (need to decide what type of hose)
Clutch 0.2" 3/16" stainless steel (Ricardo clutch input is on right side).
Electrical ??? TBD

Other considerations:

  • Primary ground wire

  • Primary power wire

Cooling Tubes


  • 8x CBM-10924 1.75” Billet Bolt on Clamp $14.99 — CBM Motorsport

Electric Cooling Pump

  • 966542 MMR Inline Thermostat Housing / Bypass Line delete $57.99 (1/2” NPT Port; Uses any traditional Chevrolet thermostat and gasket)

  • 551564 ICT Billet LS Remote Mount Water Pump Adapters with -12 An Fittings $49.99

Pierburg CWA200 Specs:

  • Operation voltage: 8-16 volts

  • Weight: approx. 2.15 kg

  • Current consumption: 15A (16.5A max.) / (approx. 0.2mA in standby mode)

  • Nominal diff. pressure: 0.45 bar *

  • Flow rate: ca. 116 l/min @ 0.45bar / 166 l/min @ 0.30bar

  • Max Speed: approx. 4500 rpm

  • Temperature range: -40°C – 128°C (water) / -40°C – 140°C (ambient)

  • Protection: IP67