If you can run a 16# radiator cap, and 50/50 coolant, you should be good with a 195* HI-FLOW stat.  Get a good electric cooling fan, too.  It will pay for itself because it doesn't run all the time (unless you have the A/C on).

If your iron heads can't transfer heat fast enough, you will hear pinging and knocking.  Sometimes wrong ignition timing or lean jetting will cause excessive heat.  So will a stuck heat riser valve on your exhaust manifold (you don't need one if you live in FL). If you can't rid the knock, drop down to a 180* stat.

Properly set up, the higher you run your engine temp, the more complete burn your fuel will get, and the longer your engine will last.

Look at today's cars.  They all last 2-300k miles and they all have 195* stats.  They also have aluminum heads (which transfers heat second to copper), moly rings, and some engines use hyper-eutectic alloy pistons (which send heat through the rings).

Hope this helps.  -  Dave Dare

Lon

Some of the common thermostats use the itty bitty hole for a scrub motor - and then surround it with sheet metal to make it fit the larger port and hoses of the Y. The NAPA 170° #6 mentioned earlier has the 1-1/2 poppet size - many of the others have the 1 inch poppet. 

The one on the left flows way less than the one on the right.

As shown here this one is modified by drilling three 3/16 ports around the nose - which adds flow and creates water movement over the "pill" that operates the poppet. This modification is the suggestion of Stewart Components - and they can supply the modified part if someone wants to order one. Otherwise i just drill my own holes in a Mr Gasket "high flow thermostat"  - just be sure you order the one for the big block Chrysler to get the right size for a Y.   

I've heard, there's a reason why stat openings are restricted to ~one inch.  Really?  Then why are all the rad hoses so large?  When your cooling system is maxed-out, and the radiator can't transfer any more heat, a high-flow thermostat makes perfect sense as a last-ditch effort.  It offers more flow at the same pump pressure, which puts as much heat at the radiator as possible.  If hot water isn't cooled by the rad, then the rad has a heat transfer problem, not your thermostat.

Last week I was in Mississippi for my first time.  I saw two things I couldn't believe:

*  A motorcycle had a CHEVY 350 cu in V8 engine.  (The giant radiator caught my attention.)  The drive chain was HUGE (probably an 80).  I asked the guy if insurance was killing him.  He said, "Not really.  When they asked what size my engine was, I told them it was 'a 350'.  They must have thought I meant CC's!"  The tank spread was so wide it would give me rickets.

*  A stock water pump on another Chevy 350, driven by an electric fan motor mounted above the water pump.  (That blew me away.)  It had a small v-belt between the pump and motor.  I'm sure the motor was thermostatically controlled.  After thinking about that for a while, I wonder why anyone needs a thermostat.   The motor was from a stock Dodge electric radiator fan.

The cooling system of the bird is pretty inefficient due to the one inch "spacer" Ford put behind the water pump that leaves the impeller spinning in "no-mans land". Small radiator face too. Very dumb. Anyway - equipped as I described, the bird runs almost exactly 100°-110° over ambient. The temp rating of the thermostat simply controls the opening minimum. At no roadspeed idle -when the ambient temp drops below 60° F temp, the engine water outlet stays at about 160°/170° and regulates. It will tolerate ported manifod vacuum to the distributor in winter - but not in summer.

This 110° rise situation can get pretty uncomfortable in summer at stopped idle. I've run a considerable number of "burndown" tests. Only the pressure cap and antifreeze boiling point are on your side. So far - knock-on-wood - the tanks have stayed connected with a 13 psi cap. My local rebuilder removed the radiator tanks, rodded it out and claims to have put the "super-seal" on the solder job - and he has an excellent reputation for keeping desert radiators intact. Fingers crossed here. 

A large percentage of drag racers have been running electric motor driven water pumps for some 25 years.  Many buy a kit with the motor, timing pulleys, and a timing belt.  I drive mine with a small V belt.  It and the blow through cooling fan are on a thermostat, so they cool the engine down after a run, then shut off.

"...and Stewart Stage 2, 3, and 4 water pumps simply will NOT operate with a regular thermostat because these pumps have no internal bypasses."
 

John, all the parts on the 350 I saw came out of a JUNK YARD!  The guy spent NO money on a kit.  I've seen electric waterpump kits, stand-alone and otherwise.  This one blew me away because it was simple and available to everyone for half-nothing.

I was simply amazed.  It got the juices going, and I thought about two-speed fans and MOS-FET designs I could do with a simple thermistor input for variable speed control.

Dave Dare

Whomever answered the phone at Stewart the day I called, estimated the three holes raised the flow capacity of the thermostat by 5%. Might have been the counter clerk....dunno. Doesn't matter if its a stocker like mine or a race car - I'll take the 5%.

Since I read the June article in "Streetrod" mag I've been toying with the idea of (1) putting restrictor washer in the bypass hose and (2) finding a way to add additional flow capacity by drilling or notching the poppet. 

Steve, IMHO, drilling more holes isn't the answer.  Your poppet thermostat already offered zero coolant restriction before any holes were drilled.  Interestingly, nowhere is this 5% mentioned in Stewart's web site.  Open means open.  Zero restriction = free flow.

I mentioned before, I think an electric fan is your answer IF your radiator is efficient enough to cool your system.  If it isn't, look for a good radiator.  The combination of radiator & fan (heat transfer) are of monumental importance for desert cooling.  I believe bypassing your thermostat doesn't do much to cool because it simply prevents your stat from doing its job.  At times you need heat, other times you need to carry heat away.

There are a couple points I do not agree with Stewart on.  One is, aluminum transfers heat better than copper.  Oh no it doesn't.  Silver is the best (put a silver spoon in hot coffee), then copper, then aluminum.  Farberware's most premium pans have a copper bottoms.  Their 'standard' set has aluminum.  I have both sets.  NO comparison, copper uses less heat to cook because it transfers much easier.  Your thermostat is made of brass (copper and zinc) and it is submerged in water.  It doesn't need holes to transfer heat to that cone.
- Dave

My water pump drive is also zero cost.  I used a heater motor from a '68 Ford I had laying around.