PLASTIC/ALUMINUM RADIATOR

This is what we feel is the best radiator for the V8 ZX. It also works well on the six-cylinder ZX car, and it weighs about 5 lbs less (including mounting brackets) than the stock 6-cylinder ZX radiator.

This radiator is made for Stealth Conversions. It is the base radiator for the 1984-1986 V8 Camaro’s, but with a thicker core (1-3/8" thick, compared to 7/8" for a stock radiator).  It is light, inexpensive, and does an excellent job of cooling. It has the correct overall dimensions to fit in a ZX car, and it has an automatic transmission cooler in the passenger’s side tank. The heavy-duty radiator for a 1984-1986 Camaro has a 1-3/8" thick core, but it has an overall width of about 30" (compared to 25.25" on the radiator shown above) which is too wide to fit between the frame rails in the ZX car.

The radiator can be purchased separately as part #ZX-121.

WEIGHT SAVINGS

The radiator shown above weighs less than 10 lbs pounds (empty). The side tanks do not hold a lot of coolant, and this also saves weight. When the radiator is filled with coolant, it weighs 15 lbs. The brackets which hold the radiator weigh 7 lbs, for a total weight of 22 lbs.

By comparison, a stock 280Z radiator weighs 19 lbs (empty), and 27 lbs full of coolant.

The radiator is positioned about 18 inches forward of the front wheels, so the actual weight reduction off the front wheels is about 6 lbs, and about 1 lb is added to the rear wheels.

RADIATOR CAP

The radiator cap on the Datsun Z will fit on the Chevrolet style radiator

Radiator Cores, above

The radiator core on the left is used on the base radiator for the 1984-1986 Camaro. The core width is 7/8" (.88"). The tube width is .800".

The radiator core on the right is used on the radiator sold by Stealth Conversions. The core width is 1-3/8". The tube width is 1.20".

The genuine Camaro radiator with the thin core does a good job of cooling the V8 Z, but some people returned the radiators without ever using them because they felt the radiator was too thin to cool well.

Radiator prices have dropped over the years and Stealth Conversions can sell the custom made radiators for less than the wholesale cost of radiators 10 years ago.

One of the reasons radiator prices have dropped over the years is due to the low cost of aluminum (Russia is now a large source of the ore used to produce aluminum). Another reason for the cost reduction is because of competition from radiators manufactured from overseas. The quality of the American made radiators sold by Stealth Conversions is first rate.

Radiator Core Designs

There are a lot of different radiator designs and different materials: Copper-brass, aluminum, 1-row core, 2-row core, 3-row core, continuous fin, louvered fin, straight fin, serpentine fin, dimpled tube, cross flow, down flow, high-efficiency core, 1-pass core, 2-pass core... etc.

A lot of the different designs have more to do with marketing than actual cooling ability.

On the left is a modern style radiator core used in everything from new Corvettes to new trucks. The tube width is 1-1/4", and the tubes are spaced at 7/16" interval. The wide tube has more surface area that contacts the cooling fins than the radiator cores shown to the right. The greater surface area results in better heat transfer.

The center radiator core is a two-row copper-brass design that is used on a lot of cars built in the early 1980’s. The tubes are 3/8" wide and they are spaced at 7/16" intervals. The core on the right is also a two-row copper-brass design. Its tubes are 1/2" wide and they are spaced at 9/16" intervals. This design was used through the 1970’s, and is similar to the stock radiator core in a ZX.

The one-row core design is the best for cooling and the lightest weight of the three radiators shown. Copper has better heat transfer characteristics than aluminum, but the aluminum is more easily formed into wide tubes, and it is lighter and less expensive than copper.

Custom 4-row core radiators do not cool the ZX as well many people believe because it is difficult to get air through the thick core due to aerodynamic restriction. Also, once the cooling air has gone past the first row, the air is heated up so that it cannot cool the second row as much as the first row, and this pattern continues to the fourth row, which does not provide much additional cooling. The aluminum one-row radiator is the best radiator we have found for the V8 ZX, as well as the 6-cylinder ZX.

RADIATOR MOUNTING BRACKETS

For durability, it is important to completely rubber mount the radiator using Chevrolet radiator pads, and making sure that nothing rubs on the radiator core.

The aluminum radiators need to be rubber mounted to protect from vibration and from electrolytic corrosion. One of the reasons the all-aluminum racing radiators don’t last long on street cars is because they are often mounted metal-to-metal.

The Stealth Conversions brackets shown above, use Chevrolet rubber mounting pads (from a 1986–2004 S-10 Truck) that isolate the radiator from vibration and electrolytic corrosion. The brackets come with the rubber mounting pads (GM part #12338053).

The brackets have alignment holes which hold the rubber pads in place for installation purposes, but silicone sealant must be used to hold the rubber mounting pads to the radiator brackets.

The brackets shown are made from Zinc Plated steel to prevent rust. Other parts included in the mounting kit are aluminum reinforcement brackets (see below), and the hardware (nuts and bolts).

The mounting kit can be purchased separately as part # ZX-625, and also includes the aluminum reinforcement brackets (see below).

LOWER RADIATOR BRACKET INSTALLATION

The lower radiator bracket is installed first, using the stock radiator mounting holes. The original ZX radiator bolts are used with the supplied flange nuts.

After installing the lower bracket, install the radiator onto the lower bracket and check for clearance between the passenger side frame rail, and the radiator side tank. There should be 1/8" to 1/4" clearance. If the clearance is not correct, remove the radiator, and move the lower radiator bracket for proper clearance, and then tighten the mounting bolts.

The reason to keep the radiator close to the passenger side frame rail is to improve clearance between the upper radiator hose and the air flow meter. It will also help with mounting the fan shroud (if used).

RADIATOR MOUNTED IN CAR

The radiator is mounted in this car as a bolt-in.

Two aluminum flat bars hold the top and bottom radiator brackets together as a rigid structure, so that thinner metal can be used for the mounting brackets, and reduce weight.

The flat bars can also be used to hold an electric cooling fan. The upper and lower brackets can be drilled to reposition the aluminum flat bar so that an electric cooling fan can be mounted to the flat bar (see below).

Upper Radiator Hose and Air Flow Meter

On the 280ZX, the air-flow meter interferes with the upper radiator hose — the air-flow meter must be repositioned. On this car, the bracket holding the air-flow meter was moved over about 1/2" and two 5/16" holes were drilled to mount the bracket to the car.

Also, the flexible rubber air ducts attached to the air-flow meter must be re-adjusted to compensate for the relocated air-flow meter.

Relocating the air-flow meter as shown will probably take about 1/2 hour, which includes a lot staring at the parts. If you do a second car, the job will take less than 5 minutes.

On this installation, there is about 1/2" clearance between the upper radiator hose and the air-flow meter.

Fan Shroud

The only difference in the cooling system between air-conditioned ZX cars, and non-air-conditioned ZX cars is that a fan shroud and coolant recovery tank came on air-conditioned ZX cars. The fan shroud improves cooling efficiency, and makes the air-conditioning work better by drawing more air through the condenser (which is mounted in front of the radiator).

On air-conditioned ZX cars, the stock fan shroud is extremely important. A shroud is not necessary with the Chevrolet style radiator in a Datsun ZX that does not have air-conditioning.

The fan shroud can be installed onto the Chevrolet style radiator, but it needs to be trimmed to clear the upper radiator hose, the lower radiator hose, and the probe on the passenger’s side of the radiator. Trimming can be done with a band saw, or a grinder.

There will be a gap between the radiator and the sides of the shroud. Foam can be glued to the sides of the shroud to seal the gap, but it is not necessary.

It will probably take an hour or two to test fit and modify the fan shroud, and install brackets, but if your vehicle has air-conditioning, and you don’t want to run an electric cooling fan, installing the fan shroud is worth the effort.

Radiator Hoses

The three hoses shown above are listed as the upper radiator hose for a Datsun 280ZX.

As you can see, they are all different. The hose on the left was purchased from a Nissan dealer, and the other two hoses were purchased from local automotive stores. The hose on the right is a Goodyear brand, part #61267, which works well for the aluminum radiator conversion.

The purpose of showing these hoses is to explain why it is often necessary to cut and splice hoses to fit an application, and why parts that are suppose to work for the same application sometimes don’t work.

Lower Radiator Hoses

The hose on the top is a stock 280ZX lower radiator hose. The Goodyear brand of hose (Goodyear part #61167) is an exact match for the Nissan.

The stock hose (or Goodyear #61167) is cut off to at the dotted line. The upper section is then attached to the elbow with a splicer and a hose reducer bushing. The elbow is a section of the lower hose from a 1998 Chevrolet Truck with a 350 V8.

The finished hose is shown on the bottom of the photo.

Note: The lower section that is cut off is used on the upper radiator hose where the hose connects to the radiator. The tight bend will help with the clearance between the upper radiator hose and the air flow meter, and it curves upward from the upper radiator fitting, which will provide clearance when using the ZX fan shroud.

Lower Radiator Hose Installation

The stock 280ZX lower hose connects to the elbow with the hose splicer and the 1-1/2" to 1-1/4" hose reducer bushing.

Installing the rubber elbow onto the radiator is slightly difficult. To make the installation easier, put a little liquid soap on the radiator outlet, and the hose should slide on easily.

Upper Radiator Hose Assembly

The upper hose assembly is made from a section of the stock 280ZX lower radiator hose (Goodyear part #61167), and a replacement upper radiator hose (Goodyear part #61267).

The two sections of hose can be connected with a 1-5/16" diameter hose splicer, or for people who want to quickly purge all the air from the cooling system, a splicer with an air-bleed valve can be used to splice the hoses.

Radiator Hose Splicers, and Hose Reducer

Hose splicers and a hose reducer bushing are required when connecting hoses to the Chevrolet radiator. Assembled hoses are shown here: upper, and lower.

If you want to use your existing hoses, or you can purchase hoses cheaply, Stealth Conversions sells a hose splicer kit which includes two 1-5/16" brass hose splicers, and one 1-1/2" to 1-1/4" hose reducer bushing as part # ZX-502. Shipping weight is 1 lb.

The 1-1/2" to 1-1/4" hose reducer bushing will stretch onto the 1-5/16" hose splicer.

The reducer bushing should be trimmed so that it overhangs the splicer by less than 1/4" so that it will not obstruct coolant flow.

The splicer with the air bleed fitting part # ZX-129. (shown immediately above)

AIR-BLEED VALVE
Part # ZX-129

The air-bleed valve mounted in the upper radiator hose, as shown above, allows all of the air in the cooling system to be quickly purged out. After filling the radiator and coolant recovery tank with coolant, install the radiator cap. Then, squeeze the lower radiator hose, and open the air-bleed valve. Any air in the cooling system will leave through the air-bleed valve. While still squeezing the lower radiator hose, tighten the valve. As the lower radiator hose expands to its normal size, it will draw coolant into the radiator from the coolant recovery tank.

Repeat as necessary until all air is purged from the cooling system.

Chevrolet and other manufactures use air-bleed valves on production cars. As an example, the LT1 Camaro and LT1 and LS1 Corvettes come from the factory with air bleed valves mounted at the highest point in the cooling system.

ELECTRIC COOLING FAN AND MOUNTING

A thin electric cooling fan can fit between the engine and the radiator, but it must be offset towards the driver’s side to clear the water-pump pulley. The fan shown is a flex-a-lite® model 116, which is 16" diameter and 3-1/4" deep. It draws about 10 amps. It is about the largest fan that can be used in the 6-cylinder ZX.

When using an electric cooling fan, it is important to protect the radiator by not attaching the fans to the radiator core. The bolts that attach the fan to the aluminum bar stock are 1/4-20 UNC, by 5/8" to 3/4" long and need to be secured with Loctite® or some other bolt adhesive to prevent loosening because the plastic brackets will break if the bolts are tightened too much.

The aluminum flat bar must be tapped for a 1/4" - 20 UNC thread for the bolts because there is little room between the radiator and the aluminum bar. Using nuts is not a good idea because they may protrude into the radiator core. Fine threads (1/4-28 UNF) do not work well in aluminum.

With the radiator and fan combination shown above, the fan will only run in stop and go traffic. Once the car is moving over 15-20 mph, the radiator’s efficient core design allows enough air to go through the radiator for adequate cooling.

The fan should be wired to turn on automatically when the coolant gets hot. We don’t like to see the coolant get above 200° F. Adjustable thermostats are available at many auto part stores.

ELECTRIC COOLING FANS AND AIR-CONDITIONING

If the car is air-conditioned, the fan should be wired to turn on whenever the air-conditioning is turned on, unless a pressure switch is installed in the air-conditioning hoses to turn the fan on when the pressures get high. For most people, it is easiest to wire the fan so that it turns on whenever the air conditioning is turned on. Most electric fan kits have instructions for wiring the fans when using air-conditioning.

ALUMINUM RADIATOR

This is the finished installation in a 1981 280ZX, with the fan shroud installed.

The stock Datsun Z radiator cap fits on the Chevrolet radiator, and the hose to the coolant recovery tank was shortened, and connected to the radiator.

AUTOMATIC TRANSMISSION

If your car has an automatic transmission, the Datsun transmission cooler hoses will have to be cut, and spliced to the Chevrolet radiator using transmission cooler fittings available from automotive stores. The Chevrolet radiator uses 5/16" inverted flare fittings.