Nice build! Start with the simple things first.
The first thing I would do is buy or borrow a temperature gun.
http://www.ebay.com/sch/i.html?_from=R40&_sacat=0&_nkw=temperature+gun&_sop=12You need to verify what the temperature actually is…….you don’t want to spend a bunch of time, money and aggravation hunting for a problem that turns out to be an inaccurate temperature gauge (over the years I’ve run into this three times so it does happen). You want to check the temperature at the thermostat housing to see what the temp of the coolant coming out of the engine actually is.
The next step is to get a thermostat in the engine. Besides its function of quickly bringing the engine up to operating temperature, the thermostats’ most important function is to act as a restriction in the cooling system. That restriction is vital in keeping the coolant in the radiator long enough to transfer heat from the coolant to the outside air.
Thinking on what is an ideal operating temperature has changed considerably over the years. In the old days we felt that a car was running hot when the temp gauge hit 200 degrees. For most modern engines that could actually be considered on the cool side. Personally I’m perfectly happy seeing any of my cars run in the 190-210 range and can even live with 220-230 if I can’t get it any better. Keep in mind that the coolant mix (anti-freeze and water) will raise the boiling point of the coolant and the radiator cap further raises the boiling by 3 degrees for every pound of pressure added to the cooling system. As long as your cooling system is in good shape (hoses, clamps, radiator etc) running a 16 pound radiator cap is no big deal.
That being said personally I would start with a 190 degree thermostat and feel perfectly comfortable seeing an operating range in the 190-220 degree area.
If you feel that that is too high then your alternatives boil down to increasing coolant capacity or increasing air flow thru the radiator.
Increasing coolant capacity means a radiator with a more coolant tube surface area. Brass/copper actually transfers heat more efficiently than aluminum. The problem is that the brass/copper is relatively weak limiting the size the tubes to a small size. Cooling capacity was added to these radiators by adding more rows of tubes (i.e. 2, 3 or even 4 row radiators). Aluminum is a more rigid material than brass/copper and because of this the tubes can be made much wider exposing more surface area and allowing a more efficient radiator. The reason I bring this up is that many aluminum radiator companies have started producing radiators with 3 and even 4 rows of tubes. The problem is the tubes are much smaller (usually 3/8”). If you are currently using a 2 row radiator with 1” tubes(2" worth of surface area), going to a radiator with 3 or 4 rows may actually end up decreasing the cooling capacity rather than increasing it. (A 4 radiator with 4 3/8" tubes actually only gives you the equivalent of 1 1/2 inches worth of tubes). Basically I don’t think you are going to get much more coolant capacity than you already have.
Increasing the airflow thru the radiator is also going to be problematic with your space limitations. Most of the aftermarket electric fans just do not move a huge volume of air. The problem is 2 fold…keeping the fan slim means limiting the pitch of the blades (less air flow) and thin motor (less power/speed). Using a bigger more efficient fan to the front of the radiator might be an option but I suspect you run into space issues there too. moparx is absolutely correct about the factory fans, if you can fit one in.
One final option is to slow the engine down. 3.55 gears are fun, but the faster the engine is turning the more heat it’s producing. A few years ago I gave my wife a car I had built several years before as my DD. She doesn’t drive a stick, so I pulled the overdrive 4 speed out and installed a non-overdrive automatic……operating temperature went up 10 degrees. Just say’n.
Sorry about being so long winded.
