Hi,
You've added more good info! I'd forgotten about the crank hole in some TR3/3A radiators (and a few TR4). That will definitely make a difference since it probably reduces the rad's capability by 10 or 20%. Of course, it's usually not a cheap/quick/easy fix to swap out a radiator, so maybe that's why I didn't think of it to include in my earlier post.
Are you sure about the reduced anti-freeze ratio? I'd heard 50/50 was optimal for cooling (as well as reducing the chance of a frozen system in colder climes, of course). Do you have any concerns about reducing the anti-corrosion and lubricating properties of the coolant mix, with the lower AF ratio?
Although anti-freeze increases the coolant mix's boiling point and helps reduce overheating, some racing venues prohibit its use in cooling systems, to prevent slippery spills on the track in the event of a crash or other radiator failure. I think that's where Water Wetter originally came from, since water by itself is less efficient than the anti-freeze mixture. (Personally, I'd only use plain water with or without Water Wetter if I were absolutely certain the figure 8 gaskets were aluminum or copper, not steel, *and* if the system was drained and flushed often... like after each race weekend.)
Yes, the long header tank was carried over from the TR3/3A on the first 9552 TR4s. It's helpful keeping air out of the top of the rad/top hose. If completely topped up, expansion will push some coolant out of the tank and onto the driveway, unless an overflow tank is installed. Coolant in the neck is usually, what, 1/2" to 1" below the top?
With a true expansion tank, fitted slightly above the top level of the radiator, you eliminate that airspace, to help insure all air is kept out of the system and modestly increasing the overall coolant capacity. On TR3s I've usually seen tanks mounted on the firewall, on the passenger side. Unfortunately, this certainly doesn't look very original.
I also forgot to mention that there are at least two types of expansion tanks on later model cars. One has smaller inlets/outlets, usually about the same size as the overflow hose barb on the TR's radiator. The other type takes a larger hose, approx. 3/4 to 1" diameter. This latest type tank would probably require a fitting of similar size be brazed or welded onto the radiator.
Again, when adding a true expansion tank (as opposed to a simple overflow catch tank), the radiator's cap is removed and replaced with a type that seals on the top edge of the hole, allows free flow of coolant to and from the tank. And, the tank itself uses the pressure relief type cap that was formerly fitted to the radiator.
Now that you mention it, I think my TR4 has had a TR3A round-end fan on it all these years! Never gave me any problems (whew!). Broken fans that holed the radiators knocked two out of three TRs out of LeMans during one of the early factory efforts. They finally got smart during a pit stop and removed the third car's fan, since it really served no purpose at an average speed of 110 mph!
Other cooling improvement options I didn't mention before:
Wrap tubular headers and/or exhaust pipe to help reduce underhood temps. This is relatively low cost and easy, but will likely make covered areas of header/pipe run hotter and wear out a lot faster. Stainless exhaust components will last longer and can be more completely and effectively covered, but add a lot more cost.
Along the same lines, ceramic coating on an exhaust header, if one is being used, can help keep heat in the pipes and reduce underhood temps. This adds $100-150 to the cost of a header, but increases it's life expectancy. It can be done to older, used tube headers provided they are reasonably sound and has the added benefit of improved exhaust flow due to smooth-coating the inside, as well.
Improved venting for the engine bay can help alot, too. Old TR4 racers used to use hood pins and/or spacers to create a small gap at the rear of the hood, but that looks pretty funky and may cause other problems (oil on the windshield for example!) The "factory" method was a pair of triangular vents just behind the 4's front wheel arch on each side. I've never liked the looks of these, so am planning fender louvers a bit farther up and back on my TR4 restoration project. These will be less obtrusive and should give about as good, maybe even better cooling.
I'm not sure if this sort of thing could be done on a TR3/3A, though. I have seen hood louvers used on 3s, but that has to be done pretty carefully and not overdone, or it might cause more problems than it solves.
An aluminum radiator is quite a bit more efficient than the stock brass type, plus offers weight reduction. But it's usually pretty expensive, may not look original and you have to be sure to use compatible anti-freeze (thankfully most is safe with aluminum, these days). Copper is even more efficient, but rarely seen and heavy.
There are high performance water pumps or impellors available, improved to move more coolant. Check with the British vendors like Cambridge, Revington and Racestorations. Someone is probably importing them into the US, maybe British Frame and Engine. This might not be too expensive, if just the impellor is replaced in your existing water pump. Also, water pump bodies are also being produced in aluminum, intended for weight reduction primarily, but will transfer more heat itself.
A side note about installing a TR water pump: Assuming an original-type ceramic seal is being used in a new or rebuilt pump, the coolant should not be fully replaced immediately. The water pump is supposed to be run dry for 30 or 45 seconds, to give the seal a chance to properly seat. If this is not done, i.e. the coolant level is completely topped up before the engine is started and the ceramic seal has seated, it will probably never fully seat and likely will seep a bit of coolant for all it's useful life and possibly shorten bearing life.
An exception to this is a pre-seated seal, where the water pump has been briefly run on a bench before installation, or if a different type of seal is used (check with the vendor). I have to admit I learned this trick the hard way, spoiling a freshly rebuilt water pump in the process. That was back in the days when we bought them cheap from the local Massey Ferguson dealer!
Another option is an oil cooler. Oil contributes a lot to keeping engine temps under control. A 10 or 13 row model will do on all but the most highly modified TR 4-cylinder engines. Kits are available from the major US vendors, but I've found it's usually cheaper to just pick up a Mocal unit (that's what is in most kits), the hoses of your choice and a sandwich plate. This does require you remove the stock oil filter cannister and replace it with a spin-on adapter and filter. When using a cooler, an oil thermostat is pretty much mandatory. Otherwise the oil can be overcooled to the point where contaminants aren't properly boiled off and vented during driving. I see where Mocal has a sandwich plate now with a built-in thermostat... a great idea! Racerpartswholesale.com, Summit Racing and Pegasus Racing are good sources for these items.
Revington TR has a passive alternative to an oil cooler. They weld a couple air tubes into the stock sump pan, running from front to rear. These allow air to pass through whenever the car is in motion and help keep the oil temperature down. Two possible drawbacks of this setup are that there is no way to thermostatically control the cooling effect (unless you really complicate matters with some sort of "gate" controlled by a thermostat). And, to be most effective, matching air pipes need to be installed in the frame cross member directly in front of the oil sump. Still, it's an elegantly simple idea and creative alternative!
I mentioned a pusher fan hidden under the radiator duct. Looking up R. Williams' ideas in the "Improving TR" book, he likes rear mounted puller fans better, feels they are less vulnerable. Of course, an electric puller fan doesn't look very original and installng one means the original fan must be removed from the front of the engine. Note: If that's done, only the fan itself and its hardware should be removed. The hub extension should probably stay in place because it provides some dampening on the crankshaft.
Cheers!
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