Radiators...unless you are converting to a V-6 engine, your radiator will need to be re-located farther
forward to a more vertical position. Some people have had success with the stock radiator by removing a
pie shaped section from the sheetmetal the radiator bolts to, with the result of swinging the bottom of the
radiator forward. Others have used radiators from different applications, using fabricated brackets. Even
stock LT-1 Camaro radiators have been installed by denting in the sheetmetal “frame-rail” sections of the
RX-7 to make some additional room.
Our radiator and bracket kits require the RX-7's stock radiator mounting points with NO modifiaction. This means that if you installed a different radiator and eliminated or modified the stock mounting points, our brackets will NOT fit.
Our brackets are designed specifically for our radiator's tank design, which features fabricated tanks and an angled/lowered radiator cap location. This allows us to mount the radiator higher so that ot will fit between the hood and the plastic underbelly tray
under the front of the RX-7. Our brackets also feature seal plates in their design to eliminate airflow paths around the core. If you design your own brackets for your own radiator, you will need to pay special attention to sealing air paths in the following areas...
...to the sides of the core
...under the core and at the sides where the wiring harnesses pass thru
...in front of the upper core in the area between the hood latch and the radiator's upper core brace
Air Flow Control...Whatever radiator you decide on, if you live in one of the warmer climates such as Arizona or Florida, you will need to pay extra attention to directing every last bit of air drawn in by the fan THROUGH the radiator, instead of around it. This means sealing off all the paths above, below, and around the rad with sheetmetal, cardboard, or foam. The main objective of airflow control is to MAXIMIZE the pressure differential between the front of the radiator (you want it as HIGH as possible) to the area in back of the radiator (you want it as LOW as possible) to maximize airflow thru the radiator core. A key component vital to accomplishing this goal is to seal the radiator so that the core opening is the ONLY way for air to flow from the front to the back side of the radiator. Any other openings will allow air to pass around the core and will bleed off the pressure differential and ultimatly hurt airflow thru your radiator core. Look for alternate flow path above, below, or around your radiator. This is very important for cooling at ALL speeds, and should not be overlooked. REMEMBER...the RX-7 has a small engine compartment with minimal exit paths for the hot air to escape from. If the air can’t get out fast enough from the rear and bottom of the engine compartment, it will simply go around the rad or fan to the low pressure area in front, reducing the amount of fresh cool air drawn in. Our radiator kits use the largest possible radiator without requiring major modifications, and our radiator brackets are engineered to seal off the paths around the rad without further fabrication.
Thermostat...Be sure to use a new high quality thermostat that features a balanced design. One almost necessary modification to your new thermostat is that a 1/8” diameter hole should be drilled thru the flat area of the disc to allow more thorough purging of any air bubbles when adding coolant. This mod also makes the process much faster, as the bubbles can now travel thru the closed thermostat into the upper radiator hose.
Heater core plumbing...The RX-7’s heater core should be plumbed in using a “restrictor” fitting. The reason is that the heater core can be a short circuit path around the radiator core for the water. In warm weather the heater is turned off, with no airflow through the core to cool the water flowing through it. The effect is that, without a restrictor fitting, a significant percentage of your coolant can circulate through your heater core instead of the radiator.
Hood weather-stripping...another exit path for the hot underhood air is at the rear of the underside of the hood. The weather-stripping there can be removed, allowing some of the hot underhood air to escape upward during slow speeds in stop and go traffic. WARNING... although this mod will result in additional removal of hot underhood air, this path will also allow underhood substances a direct path to the surface of your windshield. Oil film or steam from a blown hose could result is severely reduced visibility. Remember...this modification is only effective at low speed "stop-n-go" conditions. At higher speeds, it can work against you, as hi-speed aerodynamics cause pressure to build up at the base of the windshield, which will cause air to flow BACKWARDS into the area under the hood, pressurizing the engine compartment, causing reduced airflow thru the radiator core.
Ignition Timing / Idle fuel mixture (carbureted engines)...common causes of high cooling system temps in low speed/idle situations. Insufficient ignition advance and a lean idle mixture both contribute to high exhaust temperatures (charge is still burning when the exhaust valve opens). Connecting the vacuum advance to a manifold vacuum source is preferred. Advance should be between 12 and 18 degrees BTDC at idle. A lean idle mixture can be as simple as improperly adjusted needle screws in the carburetor, or as puzzling as a hidden vacuum leak in the manifold or carb base gaskets. Make all efforts necessary to eliminate any existing leaks.
Bleeding Air From The Coolant...It is VERY important to bleed ALL air from the cooling system. This often means searching out any internal high spots that are likely to collect air, forming pockets. It is also important to have an effective coolant recovery tank to collect excess coolant as it comes up to operating temperature, and return liquid coolant to the system as it cools off and contracts after shutdown. The pressure cap is a vital component here, forcing expanding coolant to build pressure but relieving excess pressure to the recovery tank. The cap also has to have an effective secondary seal to the upper part of the radiator neck so that the contracting coolant in the system can siphon make-up from the expansion tank instead of air from the outside. If air gets in the system, the expansion of the coolant will not build up much pressure (remember that air is compressible), resulting in a lowered boiling point. Pressure from liquid coolant expanding up to the releif pressure of the radiator cap is a good thing. Pressure from low pressure coolant flashing to steam results in a downward spiral that can only be stopped by shutting off the engine. Aviod air in the system at all costs.
Fan Shroud...If you are using an electric fan you probably already have an effective shroud. If the electric fan cannot effectively cool your engine in your climate, a mechanical engine driven fan may be the only answer. Mechanical fans normally take more horsepower to run because they move much more air. A mechanical fan placed near the radiator core may be enough to meet your cooling needs, but the addition of a shroud will make it much more effective. A simple shroud consisting of a ring of sheetmetal around the circumfrance of the fan (attached to the core with tie straps similar to those used to attach trans coolers) will probably be enough to do the job (these are commonly available in kit form thru street rod parts suppliers). If you operate in the hottest of climates, a custom fabricated full shroud may be necessary.
Chin Spoiler or Air Dam...in addition to the tips on airflow control above, an effective "chin spoiler" or "air dam" is an important tool to help maximize the radiator core's front-to-back pressure differential. The main advantage here is that the spoiler or dam keeps air in front of the car, increasing pressure to the front side of the radiator. It also keeps air from getting under the car, where it could pressurize the engine compartment and kill airflow thru the radiator core.
2....Considerations & Requirements....
4....Engine / Transmission Installation....
5....Exhaust / Throttle Cable / Accessory Drive / Pulleys....
6....Cooling / Fuel Systems....
7....RX-7 Wiring Harness Connector ID and Circuit Locations....
8....Electrical System Modifications By Circuit....