Not sure if I have a cooling problem or not. What say you
69 225 slant
Radiator/Heater core flushed
New super stant 180 degree tstat
New hoses
Added a sunpro temp gauge
Toyota fan with clutch

Gauge seemed to hit this temp also on long rides before adding the fan and new thermostat

The yellow circle shows where the gauge is
While driving this am in 90 degree super humid temps the gauge, after car was warmed up and driven a bit (about 35 minute drive). It eventually reached a peak temp of 215
Using an IR thermometer I logged these numbers
At gauge screw in 180
Upper hose 183
Radiator top 224
Cast iron t stat housing 227
Heater hose inboard by front of engine 201
Heater hose outboard by front of engine 192
Lower radiator hose 187


So what do you all think. Gauge issue?
Pull the gauge and test it on the stove?

If you are pulling 187 degree water into the engine (lower hose) then it's gonna be hard to cool the engine to 180 degrees. That's one of the facts of life they don't talk about behind the bleachers...

So the question is why is you radiator not lowering the temp of the coolant? I suggest you take a bunch of readings on the core of the radiator itself. The top should be hotter than the bottom as the water makes its way to the lower hose (since the water flows from top to bottom hose). If you are not seeing a temp drop across the radiator, that probably explains where your issue is. Maybe you have a bunch of clogged up tubes. When was the radiator last rodded out? Flushing alone is not adequate.

Uhhhhh. My guess is it hasn’t been rodded out...ever. In an earlier thread someone said it was a post 72 radiator. So.... I’ll get more readings

I wouldn't try to compare temp readings between rubber hoses and metal parts on the engine or radiator. You've got 227 at the iron T-stat housing and 224 at the top of the radiator, so there's no way the water inside your upper hose is at 187. The rubber wall of the hose is providing insulation. I'd follow Greg's advice and take some more readings across the radiator, especially at the bottom tank.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing

The top tank was around 206
Bottom 186. So 20 degree difference

The thermostat determines the minimum operating temperature, not the maximum. Go here. I don't see a problem with your numbers.

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Too many people who were born on third base actually believe they've hit a triple.

THanks dan, so what is the danger zone for a slant 6. What is the “keep an eye on The gauge it’s a lil warm and uh -oh....?

You're not dropping enough through the radiator....IMO you should see around 140-150 degrees by the time it reaches the bottom near the hose. that allows you to heat the water 30 degrees before it goes back through the radiator. Keep in mind the water going in to the radiator is hotter than it will be if you cool engine with cooler water. It's a vicious circle type of thing...

Those are all rough numbers but they're typical of what I see on an engine that's cooling properly.

One other point...that 155 degrees you see dead center sounds good but there's a fair chance it's colder than the rest because the tubes there are plugged solid and aren't getting any hot water to make the temp read higher.

But I stand by what I said first...your inlet water (lower hose) is too high. Bring it down and you'll see a cooler engine and a cooler top hose as a result.

So acceptable but get the radiator looked at to get it better.

If you are not seeing boiling in hot weather and it runs well, you are probably good to go. That said, it would not hurt to clean/recore/upgrade the radiator. I have run these engines at 215-225 sustained temp on the gauge through deserts and up hills and on road courses and not seen any long term problems.

Lou

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