Oil Temp Sending unit question

[awdbandito]

I have a '75 2.7L with S cams, RS pistons, and Webers.

No external oil cooler.

It has always run what I thought was hot.
Today it is 90F and I was out driving and it was running around 250 once I got into traffic and only dropped a little on the road.

I got home and started hitting areas with the IR gun and it read much cooler.
IR gun at the temp sender - 220F
IR gun at the oil tank - 218F
IR gun on the sump plate - 240F

All these readings were with the car running at idle and the temp gauge was at 250 or just a tick above.

Could I have a bad sender?
Could I have the wrong sender?


I seem to remember that using the wrong sender with an older gauge shows higher readings but I can't find that post anywhere.

Anybody have some input?

The car needs an external cooler, no doubt, I'm just trying to figure out if it is really running as hot as the gauge indicates.

Thanks

[cabmandone]

Originally Posted by awdbandito

I have a '75 2.7L with S cams, RS pistons, and Webers.

No external oil cooler.

It has always run what I thought was hot.
Today it is 90F and I was out driving and it was running around 250 once I got into traffic and only dropped a little on the road.

I got home and started hitting areas with the IR gun and it read much cooler.
IR gun at the temp sender - 220F
IR gun at the oil tank - 218F
IR gun on the sump plate - 240F

All these readings were with the car running at idle and the temp gauge was at 250 or just a tick above.

Could I have a bad sender?
Could I have the wrong sender?


I seem to remember that using the wrong sender with an older gauge shows higher readings but I can't find that post anywhere.

Anybody have some input?

The car needs an external cooler, no doubt, I'm just trying to figure out if it is really running as hot as the gauge indicates.

Thanks

I had the old style (numbered gauge) sending unit installed on the newer style gauge and it always showed high. I put a thermometer in the tank after getting the engine up to temp and it only showed 180. If you need a sending unit for a 75 style gauge, let me know. I've got a working sending unit I could send you for the cost of shipping.

[awdbandito]

That would be awesome!
I'll send you a pm with my address and I can shoot you a paypal payment.
Maybe the sender is a bit off, or maybe my measurement technique is off.
Thanks.

Originally Posted by cabmando

I had the old style (numbered gauge) sending unit installed on the newer style gauge and it always showed high. I put a thermometer in the tank after getting the engine up to temp and it only showed 180. If you need a sending unit for a 75 style gauge, let me know. I've got a working sending unit I could send you for the cost of shipping.

[javadog]

Just check the temperature rating on the sending unit and compare it to the oil temperature guage you are running. The number is stamped on the sending unit.

JR