How do I drop my highway temp 8°?

[69hugger]

I'm going to suggest a very easy trial. I know many here will scoff at this... a few years ago I would have too.
But after I did this, my cooling issues vanished. It is simply see what happens if you remove the thermostat (gasp).
I have a '69 Camaro, 534" big block making 700 hp. My cooling system consists of the 1000 hp rated Be Cool rad w/ twin 11" Spals, and a Stewart water pump. The fans are ECM controlled to come on at 190, and shut off at 170.
When I ran a 160 deg. stat, it would run hot (210-220 +) only if stalled in traffic on a hot day, and take forever to cool down when I'd get moving again.
My very old school engine builder kept telling me to ditch the stat. I thought he was crazy. I'd cite every article ever about how doing so would speed up the coolant flow so the coolant was not removing enough heat from the engine, needing pressure in the block, etc. I was chasing all the stuff you are talking about here. Fan CFM, sealing air leakage cracks, water wetter, blah blah blah.
A few years ago, I was beating on the car pretty hard, and the cooling system blew. Coolant exploded everywhere. The engine bay was drenched. Only after detailed inspection did I discover what happened. With that flow restriction, the cooling system had created so much pressure the rear seal on the water pump had blown out.
I finally tried his suggestion. I have not run a stat since. And the car has not seen 200 degrees since. It normally runs almost exactly 100 deg. hotter than ambient. 80 degree days it runs 180. 50 degree day it runs 150. And makes no difference whether I'm on the highway or sitting in traffic with the A/C on.
I know it sounds crazy. I know the experts will scoff at this & cite why it won't work. And it probably won't work in every case. But in 1/2 hour you can try it. What do you have to lose?

[Vegas69]

A high flow t-stat may be a good compromise to none. If the coolant temp is 150, oil temp could be 150-170. Far from ideal. The moisture won’t burn off very efficiently and your oil pump will work harder. That can lead to distributor gear wear and failure. Lubrication is typically superior with reasonable oil temps. No stat will lead to a long warm up cycle too. A reasonably light synthetic would be my choice if you try it.

No stat in the summer is another option. I can see the benefit of the flow assuming the radiator can take advantage of the extra volume.

[Beechy]

Mike.
A few observations from my daily driven 68 Camaro, mild cam 350 auto, p/steer, no air, no oil cooler, stock brass radiator with trans cooler ports, some kind of Ford v8 electric fan with shroud and flaps, Davies Craig electric water pump with no thermostat. Travelled 120,000 miles so far, mild San Francisco type climate.

Maybe dumb luck with radiator sizing/water pump output (EWP80 running ALL THE TIME) but warm up times are normal despite NO thermostat, coolant temps always normal .....180 most days at all speeds, 200+ in stop/start.

Oil temps are mostly ALWAYS a few degrees cooler than coolant.
-Exception to this is starting quickly on cold morning and driving conservatively at freeway speeds, the oil can barely crack 120 = BAD. As soon as you get on the gas the oil temp will catch up.
-Also, getting on the gas at any time will see the oil HOTTER than coolant quite quickly, as much as 250, and take forever to come back down but will stay 5* hotter than coolant.

Oil has to be approx 180 to do its job, eliminate water and warm the crankcase......just like Todd said ^
Oil starts to break down 260+.

Every carb equipped car should have a 4-wire fuel/air meter, $200 will save you the first unnecessary tune up. Check timing at cruise rpm.
Normally a thicker radiator creates issues in traffic because fans struggle with heat soak but ok at speed because airflow, so not always a happy solution.

NEVER use a pusher fan, they're an expensive way to block airflow.

A/C condenser should be 3/4" clear of rad core.

You have done great with flaps and foam seals but fans for 200 h.p. does not compute.
I hope your first post is a typo where u say BBC with 1.25" rad outlets.....stock SBC is 1.5".

FYI.....Covid boredom got the best of me and I moved that stock radiator under the trunk and added an EWP130 under rear floor.
17 years ago I had built the trunk floor higher to accomodate the rad but never had time to do it.
Why? Because race car.....corner weights.
Outcome? NIGHTMARE....don't do it.
It runs cooler so far but spikes in cylinder head temps take a few miles to settle down