Q: Colder thermostat worth the budget funds?

Just cut the center out of the thermostat and reinstall the outer ring. This will slow the coolant down enough for good heat transfer to take place, but it will also prevent any stuck thermostat issues. It will take a few minutes longer for your car to warm up, but if it's not anyone's daily driver, who cares?

There are some people who will tell you to throw away the thermostat altogether, but on a few cars this will cause overheating. I don't know about your 'bird.

You definitely don't want to remove the whole thing but taking the center out is OK. Even better would be to find a way to stick it open so you would maintain the right flow balance of the cooling system.

On most engines the thermostat is a calculated orifice that splits the output from the water pump between the block and the radiator. Taking it out completely upsets this balance and as Erik states will cause the engine to overheat. Taking out the center might make it run a little warmer at the end farthest from the pump.

We went to a colder one but that was because we were switching to a fail open style anyway.

Although when it comes down to it the oil cooler we added did drop the engine temps so if your worried about engine temps and haven't done that, its something you should consider.

We run without a thermostat at all - simply as a reliability measure. A stuck (closed) thermostat could be a race ended.

That being said - the temperature at which the stat opens is, for us, fairly insignificant. With a properly operating cooling system, standard stat would be fine. Remember, you should be seeing head temps of about 190 (250 at the plugs). That's the right number to run (colder is not necessarylilly better, btw)  As long at the stat (in-head type) opens at less than that - it's gonna just stay open.

Unless you're making much more power than stock, I think there is a problem. Stock hardware is usually quite overbuilt to make up for bad maintenance and severe duty (racing falls under this). I've had a boost gauge connected to the cooling system before to watch the pressures, and dual water temp gauges (one at head one at radiator outlet), and it certainly helps to see how temperature and pressure are inter-related.

An oil cooler would make a HUGE diference in water temps, sounds like you either have a bypass problem or something making it flow too fast/slow, or not enough/too much pressure.

There are thermostats that have dual circuits (most Japanese cars are like this), where a second little theromstat plate is at the base of the big thermostat. With that open, it would circulate water back through the block/head without moving the water to the radiator.

So you don't mind wearing your engine much more, using more fuel, or making your cooling system not even work properly in the first place, all because you think that it might fail? Its just plain dumb and advised against in just about every racing book I've read.

edit: here's the text from Modern Engine Tuning, by A. Graham Bell (haha)

Our motor is stock, but it is old and we certainly didn't have any problems with the engine running cold. We let it warm up before racing it, which didn't take long, so no problem with all that extra wear-tear.

The oil cooler did not decrease engine temperatures that we could tell, and we ran BW all day a 210-220F (water) and oil temps were about the same. I'm glad it was December.

On the freeway the water temps hold steady at about 150F in cool weather, such as near Monterey, and over 180F in warmer weather, near Sacramento, on the same day/trip, at the same speed, which happens to be near our top speed at a race except on longer straights, 80 mph. So I think there is something about a '69 that never came with A/C having a marginal cooling system. I remember back in the 80's that is was common for stock street cars to overheat on HWY-17 over the mountain to get to Santa Cruz.

we put a transmission cooler on our setup and now I actually fear we may have taken too much heat out of the system as it seems like it'll barely hit 180F even in the heat like Summit. My call would be, that if you're concerned about cooling; replace the water pump, hoses, and get a "fail-open" t-stat. between those two you shouldn't be having a cooling issue unless there's a head problem.

Overheated is such a vague term.....  Just like I say in the video "it was over 220F..but I didn't let it get to 230F".....so I did a good job right?

From a tuner aspect, running a colder range thermo would require you to run colder range spark plugs and be tuned to take advantage of it... just simply sayin...

I also read modern engine tuning, but then i read an FAQ in a PDF  by Davis, Craig a maker of very high quality electric water pumps for race applications

Q- Is the idea that coolant can pass too quickly through a
radiator true?

A- The “pump too fast lose less heat” notion is very popular and
many experienced mechanics are very attached to it but ... it
is a fallacy. Davies, Craig has been carrying out research and
development for over a decade on a number of projects and has
never been able to pump genuine liquid coolant faster and lose
less heat. In all car engines, when the mechanical pump reaches
cavitation speed, coolant turns into a gaseous state which is
compressible (liquid is not), and the real flow rate of liquid coolant
drops even though the mechanical pump has a higher rpm, and
so heat loss drops. The engine temperature then rises. And it only
seems like the flow rate is too fast, and the coolant is spending
too little time in the radiator to lose its heat etc.

I think radiator shrouds are just as important as having the proper thermostat. Having a shroud that seals up nicely and forces the air through the radiator is important. Remember air is lazy just like your asshole brother in law and will go wherever it's easiest.

I think I saw someone mention on here before that they had good luck with garden edging installed below the front bumper as a simple air dam. It keeps the air from going under the car instead of through the radiator.