Overheating 283?

[Ernest C.]

I have 96 miles on a freshly rebuilt 283, 270 HP engine with hydraulic lifters. My temperature quickly goes up to 212 degrees which is alarming. I have purchased an infered thermometer and it reads 125 degrees when my gage is 212. I hope it indicates my gage is the problem as long as infered thermometers are reliable. My question is how much confidence should I put in my thermometer?
Thanks

[Richard M.]

Re: Overheating 283?

Ernest....I'd boil a pan of water and see if it's around 212. That should prove or disprove the thermometer....

Chances are you have a new temp sending unit which may be way off from the originals. I don't have the specs here but I recall past discussions on what the readings should be at various temps.

Rich

[Steven B.]

Re: Overheating 283?

I have 96 miles on a freshly rebuilt 283, 270 HP engine with hydraulic lifters. My temperature quickly goes up to 212 degrees which is alarming. I have purchased an infered thermometer and it reads 125 degrees when my gage is 212. I hope it indicates my gage is the problem as long as infered thermometers are reliable. My question is how much confidence should I put in my thermometer?
Thanks

'Don't know which IR you have but you can test it on something you are certain about temp. by comparing it with another thermometer. IF the IR comes out OK you can check your thermostat in a pan of boiling water. I found a coouple of times my temp gauge and sender was the problem.

Do you have a 270 with solids, a 245 with hydraulics or put hydraulics in a 270 along with cam change?

[Mark P.]

Re: Overheating 283?

You should put a traditional thermometer in a pan of water and heat it up and check with your electronic thermometer at different temperatures.

The way I remember it a couple weeks ago when I brought my 327 up to operating temperatures and shot the thermostat housing with my electronic thermometer near the hose you can almost see right when the thermostat opens. The temperature rose to 180F when it opened and the temp jumped 20 degrees

[Ernest C.]

Re: Overheating 283?

Steven
I have a 270 with hydraulics and a cam change. I will boil water now and see what my IR reads.
Thanks

[Jack H.]

Re: Overheating 283?

Something's rotten in Denmark here. You should be getting IR thermometer readings in the range of the thermostat you installed with the engine warmed up and running at idle for a SHORT period of time. Typically, that would be 160, 170 or 180F depending on the specific thermostat you installed.

A good place to 'shoot' the temperature is at the bottom side of the radiator hose, adjacent to the intake manifold. That's pretty close to where the temp sender is mounted and the hose being rubber, is predominately heated by conduction from the coolant coming out of the engine. The reading of 125F is way to low to be believable...

Once you've got a better handle on what the actual coolant temp is, you can start to trouble shoot the car's temp reporting system.

As others have said, modern service replacement temp senders have a reputation for being 'off'. BUT, it takes two to tango!

The temp sender has to match factory specs AND the temp gauge has to be calibrated accurately. So, you start the troubleshooting process by getting the engine freshly warmed up and measuring the actual resistance of the temp sender.

Disconnect the wire from the temp sender and measure its resistance from the brass contact terminal to ground. Compare that resistance reading to the factory specs of the temp sender. Search the archives and you'll find a temp vs. resistance graph I published long ago. That'll tell you where you stand with the basic sending unit.

Next, check the gauge itself. With the engine running and rev'ed to get the generator up on its 'cut through' curve (battery voltage in the 14-15 VDC range), connect the wire from the temp sender to a 40 ohm resistor to ground.

That will simulate a bona fide engine overheat situation and your temp gauge ought to read in the 225-240F range. Remember, the system was NOT designed to be highly accurate at mid to low range temperatures. That's why there are almost NO temperature gradicules on the gauge face until you approach the 'red zone'.... That's where the system WAS designed to be highly accurate.

[David F.]

Re: Overheating 283?

Update on my overheating: I plan on replacing radiator and fan clutch, but haven't started yet (To Hot to Work at 100F ambient last week). I will be at Carlisle this week to do a little shopping for the parts I will need.
David

[Edward B.]

Re: Overheating 283?

But wait, are you really overheating? Check and recheck the actual engine operating temperature independent from the instrument panel gauge before you incur needless expense and labor.

[Duke W.]

Re: Overheating 283?

IR guns typically read a 4:1 cone, so you need to hold the gun very close to the surface being measured. Otherwise it will pick up surrounding component temperatures whether higher or lower and average the reading.

Dukr