Tech Tips

Radiators & Cooling

This is a little long but hope it might help on some of cooling problems I have read about. After 20 + engine conversions into jeeps, each with its own unique cooling problems, I have developed a few points that may help.

1) Radiators are made of several configuration, the primary thing in comparing cost is to make sure that apples are compared to apples!! The number of rows in the core is the first thing but is no more important than the number of tubes and the fin count. The typical wagon radiator without the tow package was a 2 row 32 tube 10 fins/inch with a flat top tank up to the late 80s. Tow packages was typical a 3 row 32 tube 10 to 12 fins/inch.

A high efficient radiator will generally be a 4 row core with 42 tubes and a minimum of 16 fins/inch. The high efficient radiators will cool approx. 50% better than the standard 3 core unit.

The flat top tanks were very weak and developed cracks on the sharp corners. The newer round tanks will survive high heat and vibration much better. Always a catch, the high efficient cores will run from 30% to 50% more money.

There is a shop here (Colo. Spgs.) that has the new 3 row stock unit with round tanks for $175.00. I posted earler that a high efficient 4 row unit would be around $285.

Other changes:

The trans cooler is in the radiator most may have a additional cooler, but generally mounted in front of the radiator. If this is moved to the rear of the vehicle under the floor it will help considerable. The trany fluid is running about 250°, this is dumped into the cooler in front of the radiator superheating the air going into the radiator. I have mounted a small heater motor and fan so additional air flow can be created on the remote cooler.

Engine oil also adds to the problem as it will generally be in the 225-275° range with water temp around 200°. a remote oil cooler and fan again mounted to the rear will cut cooling problems considerable.

A completely shrouded fan will pull at least 30% more air than a open unit. I have gone as far to glue rubber all around the shroud to prevent any air from being pulled around the sides of the radiator. I am currently using a stock jeep plastic shoud and works great. if you build a shroud the fan should not be into the shroud over 1/3 of the blade width. To much shroud can be bad as extra noise and turblence will decrease its efficiency.

Fan size and pitch are vary crital as to the amount of air is being pulled through the radiator. the pitch on the blades determines the amount of air is moved. this can be checked by simple laying the fan on a flat surface and measuring the height of the blades. I have found that the 19-1/2" 7 blade fan from a GM??? 454 works quite well on the jeep engines. These generally run a clutch and the clutch must be matched to the fan size. if to small it will not lock up and allow the fan to slip when needed the most.

The under hood temp gets very high and the hot air must be allowed to leave the engine compartment. the rubber dust guard on the inner fender well that go, sometimes down to the fram, hinders the air flow. If thes are removed the exhaust heat and engine heat can escape easier. Before modifications, I was actually boiling the windshield washer fluid causing it to spit water out on the windshield.

Hope this has not been to long and boreing and helps some of you with the heat problems