costpenn

OK - am worried about engine temp. Can has a 455, no air, H/D cooling, 4 row Harrison radiator, new water pump. blah, blah, everything. The temp on the gauge - today with outside air being around 100 degrees and idling for 10 minutes after about 5 miles of hard driving - is reading at the 3/4 mark. It always been rocket lore to me to be worried about anything over 3/8's on the gauge, so I bought one of those laser temperature gauge thingies from Harbor freight. Actual temperatures - with gauge at 3/4 are:

Thermostat housing - 208
Valley between timing cover and front of intake - 195
LH cylinder head (there the big letter is ) 211
RH cylinder head (same location) 205
Radiator by the inlet hose 197
Radiator by outlet hose 180
Temperature sender 218
Intake by sender 208.

Are these temps dangerously high? Or is it a 40 year old gauge out of calibration? My tach reads ridiculously high - I'm going to send it in to be recalibrated soon.

Also, immediately after shut down, the fan clutch is not locked up at all - I can easily move it. Should in not under these circumstances be almost completely locked?

Thanks

costpenn

oldcutlass

I suppose your using an IR gun of some sort. I would buy a mechanical gauge and install it temporarily in place of your stock one and see what it reads. I'm willing to bet your temps are fine for an ambient 100 degree Texas day.

On the fan clutch, if you feel it's in need of replacing replace it.

72 w29 all green

The temperatures you got almost mirror what i got Saturday using an "el cheapo" Cen-tech digital thermometer (biggest difference: i got a reading in the 160's at the radiator outlet). Rocket Rallye Pac gauge reading on mine: needle pointed to the "halfway" mark, and will read just below that mark while driving. By the way, before my engine was rebuilt, the needle got no higher than about 3/8 .

For the fan clutch, what do you mean by "not locked up at all"? You should feel some resistance, a soft drag of sorts, when you try to spin the fan. If the fan spins freely, replace the clutch.

The temperatures we are getting aren't dangerous but i'd certainly be happier if they were a good 10-15 degrees cooler.

Lady72nRob71

These are not dangerously high but it is worth attention.
I have one of the cheapo harbor freight IRT's and it is withing 2* of my expensive one. So the readings should be adequate.

You can only test a fan clutch engaging by popping the hood at idle while the temp is up there.
You should hear a roar of air being blown.
As a quick test, take an 8x11 sheet of standard weight copy paper (not the rice-paper varieties you may have at the office!), fold it in half on the long edge, and hold as in the picture below.
The air should whip it around and fold it back immediately.

I had a bad clutch on Lady and it did similar as yours.
If you want a clutch to try out, (or buy for cheap if it works), let me know.
It is an almost-new-in-box heavy duty Hayden that I replaced with an AC delco. It has 200 miles on it...

oddball

The clutch may or may not be locked up when you shut down. Not a great test. The fluid will be nice and hot, so the fan will turn quite easily if the little bimetal strip doesn't have the valve engaged. Over the past couple of weeks mine has engaged when pulling away from a red light then released after a half mile or so. So if yours hasn't engaged at all on these 95deg days, then it's probably bad.
I don't trust IR thermometers for anything other than comparisons between readings. Their reading is very sensitive to the material reflectivity, so may not represent the actual temp. I'd throw on a cheap mechanical gauge for a little while just to verify the real temp. As long as it's within 20deg of your thermostat then it's doing fine. IMO, going up to 220 is not necessarily bad, but I wouldn't be happy.

jpc647

Really? I always was told anywhere between 190-210/215 was perfectly normal. Especially on a hot 95* day.

My442

The Rally Pack temp scale is non linear.

The first hash mark (at 1/4) is 180 degrees.

The middle hash mark is 210

The third has mark is 230

Pegged is 250.

dc2x4drvr

I took my 442 out yesterday, drove it 20 miles, 190 on mechanical gauge, A/C turned off.

Lady72nRob71

As much as this is said, I find the IRT's to be pretty darn accurate on anything but chrome or clear surfaces. I have checked them against mechanical engine gauges and they are within 5*, close enough for this type of checking.
Just make sure the unit is within half an inch of the test subject and held steady for the shot.

costpenn

Thanks Rob for the help in the sampling technique. Going to check them again - I was not consistent in how far I held the device from the surface being sampled.

Lady72nRob71

Great - let me know how it goes.
However, if the gauge rises at idle, I would be suspecting the clutch.
I will be at a car show this Saturday in the town of Murphy, just down 190 from you. At the Country Burger at Murphy road and 544 (Plano Parkway).
Come if you are bored - the more Olds the merrier!
A friend of mine will be bringing a very nice surviving 73 Pinto wagon as comic relief!