When to Use Custom Engine Cooling System？

asphalt_gundam said:

For starters we should address the plastic/rubbery air dams and ducting that either rots away or nearly everyone foolishly throws in the trash when they work on a car....Yes I'm speaking from experience. This is because a large number of overheating problems I've ever dealt with had to do with air supply THROUGH the radiator. Just air to the radiator isn't good enough. It needs to be forced to go through. This was highlighted for me last year when I traveled to PPIR for a race and had my car setup with no cooling problems....at nearly ft lower elevation. Overheating in couple laps was fixed by taping up any gap in sheet metal and shrouds that was in front of the radiator. Even jabbed a towel in underneath the radiator to seal the gap that the rubber isolators held the radiator up from the core support.

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Another massively overlooked cause is the tune. An engine with too much timing (at cruise or under throttle) or a lean air/fuel ratio is just waiting to overheat. This is especially evident with older carburetted cars that never get properly tuned. Know a guy who just slaps stuff together and "is so good" he tunes timing by ear...yea his overheating is likely a E36 M3 tune. I can't drive this point home enough...Just check it so that you KNOW! A great example here is a car with a great radiator/fan setup and only overheats when cruising after an hour or so, or sitting in traffic (which lack of airflow also contributes to). This particular engine when dyno'd was ok on timing but was near 17:1 AFR...even at wide open. After some tuning adjustments the engine gained 28HP, started easier, ran cooler, and was all around made for a much better car.

Hard parts...Is the system clean of gunk, rust, debris? If you experience overheating after hard pulls...you sure the water pump is working? I've seen an impeller get loose on the shaft when hot and quit pumping! Leaks? Kinked hoses? Restrictions? T-stat working? Head gasket blown? 

Ready for system design yet? I've been looking into this recently. So there is the "closed system" style with cap that vents fluid/pressure into a catch can. Works well and used for decades but not the most effective. Then we move up to more modern style of "pressurized" or "recovery" in which there is a recovery tank with intentional air pocket that acts as a spring in the system. Here the goal is for the system to never let coolant or pressure out unless it exceeds the cap rating. All modern cars are designed like this OEM and it is a much better system. Again....how many people just rip all this "unnecessary" stuff off a car when building it for performance? An explanation here between the two before someone says "but the closed system is pressurized"...yes but in the closed system you often see the coolant level when cold is a few inches down in the radiator. Collapsed hoses is another symptom of this too. The pressurized system with the recovery tank air spring is to keep the radiator full at all times and even when dead cold have zero or positive pressure still in the system. This is evident on newer cars when opening the cap when cold and getting a pressure releasing hiss. These are more efficient due to the coolant being "full" all the time and the maintaining of pressure in the system.

Pressure: Here it is widely agreed that higher pressure makes the system more efficient and raise the boiling point. Over a few hours of searching I couldn't find any real word data on how much efficiency increases or what that means for temps during cruise or on track. Only the increase in boiling point could be found. Some racing runs over 50psi but it obviously takes a very dedicated and properly built system to handle that.

As for the original question of 2JZ and Big Block Chevy i'd bet my money on little or no shrouding and poor tunes.

Steps 1, 2, & 3:

We've installed our 1.8-liter Miata engine in the body of a MGB, and to keep it cool we're going to use
a little local knowledge: -'80 MGBs came from the factory with their radiators mounted a little farther forward in the chassis. We're going to duplicate that cooling system setup to provide a little more room for our transplanted engine. 

While the radiator mounts for these -'80 cars are available from suppliers like Moss and Victoria British, we chose to make our own using a technique called hammerforming. (We detailed this process back in our November issue; visit the Features section of grassrootsmotorsports.com to read the full story.) Note that we haven't drilled holes in our hammer-formed mounts. That step, we've found, is best left for after installation.

While the radiator mounts for these ''80 cars are available from suppliers like Moss and Victoria British, we chose to make our own using a technique called hammerforming. (We detailed this process back in our November issue; visit the Features section of grassrootsmotorsports.com to read the full story.)

Note that we haven't drilled holes in our hammer-formed mounts. That step, we've found, is best left for after installation.

Steps 4 & 5:

After fabricating our new mounts, we used measurements from another MGB to decide where to clamp them in place. We aligned the clamps with each other using some angle iron; an angle finder ensured that the mounts were perpendicular to their base.

Step 6:

We marked the locations of the mounts so we could remove them and drill the holes needed for the plug welds that will secure them.

Step 7:

Once we welded the mounts in place, we clamped the radiator in position. Then we marked the radiator's mounting hole locations, unclamped and removed the radiator, drilled the holes, and bolted the radiator, back in.

Explore more:
What to Consider When Choosing a Cooling Systems Manufacturer?

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Steps 8 & 9:

Time to address the fan, and this is where sticking with our factory parts strategy paid off: We simply ordered a complete set of fan components for a ''80 MGB and bolted them in.

Step 10:

Next we had to hook up the hoses. The Miata's stock lower hose setup features a pipe in the middle, and a previous swap taught us that we could retain it with only a minor adjustment to the length of the factory hoses.

Step 11:

It's hard to get a picture of the whole installation, but this shows how the hose and pipe work their way to the lower radiator outlet.

Step 12:

For previous swaps, we've made a little bracket to secure the pipe's mount to the car itself.

Step 13:

However, this time we had some interference. Thank the air-conditioner compressor bracket that was in the way.

Step 14:

We decided that a band clamp with a spacer could do the job. A 10-32 screw would hold it in place.

Steps 15 & 16:

We used a nut insert tool to put a 10'32 bung into the MGB's frame rail.

Step 17:

The lower hose installation worked out well, and the bracket will do a good job of isolating engine shake from the radiator. By the way, shaky radiators are an issue with a lot of swaps, and at-risk radiator components usually reveal themselves after a few hundred miles with the new engine.

Step 18:

The upper hose setup looked pretty straightforward, as it just needed to cover a pretty short distance. The problem was our strategy of using only MGB or Miata parts: Initially, none of the hoses we looked at could make the link.

Step 19:

Success! We finally realized that a section of a lower hose for a ''76 MGB would do the job. It just barely fit our strategy, but it worked well in the end.

Step 20:

Finally we had to deal with filling the system. We got a bung and cap from Summit Racing and had a radiator shop put them on our MGB radiator.

Step 21:

Our last step: installing the stock MGB expansion tank, which also houses the system's pressure cap. We put the tank on the driver's side fenderwell.

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