Radiator Relocation Pros & Cons
I have a question about relocating my radiator to my bed. It seems that every time I go out wheeling, the first thing that happens is that I bury the front end right in a big mud hole. I can even hear the mechanical fan hitting the water. I always make it back out of these big mud holes, but it leads me to believe that having my radiator in the bed would be better than right up front.
I drive a '70 GMC 3/4-ton 4x4 with the 350/TH350/NP205 combo that was a longbed, but I did a custom shortbed conversion which only cost $350. If I put my radiator in the back, should I run a stock pump? How about an auxiliary pump? Could you refer me to a good source that knows this stuff?
Mounting the radiator in the rear isn't going to be as easy as it first appears to be. The mounting system is going to have to be well engineered and one that will allow some radiator movement to prevent it from cracking any seams. You will need a very large electric fan for proper cooling and a properly designed shroud. A lot of off-road race trucks mount the radiator in the rear for both radiator protection as well as weight distribution. They also use some very expensive aluminum shrouding and duct work to get the air in as well as out. However, your stock engine doesn't have the heat exchange needs of a 600- to 800hp race motor, so you won't need to go quite as high-tech.
I spoke with Jack Wilson, the tech guy at Stewart Components (www.stewartcomponents.com). The company makes some great high-volume mechanical pumps as well as inline electric booster pumps. He confirmed my thoughts that you must focus on maximizing coolant flow and/or velocity at all times. He feels that adding the inline booster pump is a must to help achieve this. Using the largest connections possible with the fewest bends and turns will help as well.
Whatever you do, don't try to run rubber hose the full length between the engine and radiator. For one thing, it causes way too much friction loss, and secondly, it will be subject to abrasion. Use only rubber hoses at the connections between the radiator and the supply lines. I would start out with the pump that you presently have and see what happens. You'll probably find that you will have overheating problems because there just isn't enough flow due to all the restrictions of the longer coolant travel and the friction loss involved. Stewart makes a really great electric pump that goes on the suction side of the radiator. This is a very quality pump made for racing, and while a bit on the expensive side, it will most likely outlast your truck.
Tech Letter Of The Month
Multi Generation Chevy
I am building a '55 Chevy 4x4 pickup. I used '76 Chevy running gear on the '55 frame. With the front axle mounted on the original springs, the knuckles are tilted forward (negative caster?). On the '76, they were tilted to the rear. Is this a problem? I know the OEMs use positive caster to aid in tracking and re-centering the steering, but the truck seems to drive alright. I have seen other trucks with the axle mounted this way. Did they cut and rotate the knuckle? Would you in this situation? I would rather not change the spring mounts, as I would have to lower the rear mount excessively.
I used a Nissan steering box ('80s Pathfinder) because it mounted the gears above the frame. It works okay, except when you're stopped-it will not turn at all until you start moving again. Is this a pressure problem? I'm using the Chevy steering pump. Any ideas/help will be greatly appreciated.
The tilt of the steering knuckles is what is referred to as the caster angle. For the best handling, the top ball joint should be tilted to the rear of the vehicle or in a positive position. Caster angle usually is between zero and 8 degrees measured from vertical. With the negative caster angle you now have, I am really surprised that the truck goes down the highway in a straight line instead of like some well-used shopping cart.
You don't have to remount the springs to fix this. You can place special tapered shims between the spring pack and the housing mount to tilt the steering knuckles rearward. These shims are available from any suspension company. When doing this, keep in mind that the pinion yoke will be turned downward, so make sure you don't end up with the U-joint binding on full axle droop. In reality, the operating angle of both the axle yoke and the transfer case yoke should be within about two degrees.
As to your steering problem, yes, it sounds like lack of proper pressure and/or volume. This could be because the steering pump you're using is worn out, or that the pulley ratio is not correct and the pump at low engine speed is not turning fast enough to provide proper volume/pressure. Or the Chevy pump works at a lower volume/pressure than what the Nissan pump takes. Take a look at the West Texas Off Road website (westtexasoffroad.homestead.com). There you will find instructions for some simple modifications to your pump that can increase both volume and pressure.