Hi All,
Quick question for all. Back story: I've got an all original 1976 Cutlass Supreme, with the 350 pair. The engine has not been rebuilt, but cared for and it runs beautifully! I've recently worked the AC back to health, blows cold air nicely in this Arizona heat. When I switch on the AC, it seems to really put a load on the engine, as in it sounds like the AC bogs it down when the clutch kicks on, and the engine temperature drives up quickly! Admittedly, I'm a bit skittish when it comes to letting the engine get hot, and the AC seems to drive the engine temp upwards of 205, maybe higher. Everything runs fine, but my question is this behavior normal? It's a new AC compressor, fairly new radiator and no leaks. Runs nicely when the weather is cooler, but now that the temp here in AZ has reached 100, I'm worried about pushing the engine too hard/hot by also running the AC.

Any advice is appreciated!
james

 

Seem to remember the a/c cars had a solenoid to boost the idle mounted in front of throttle linkage.

 

Yes, it is normal for that type of AC compressor to load the engine. Back in high school we used to joke that it must take 50+ horsepower to drive the compressor.

Whereabouts in Arizona are you?

 

It sounds like what you have is reasonably "normal". The A6 compressor does require significant horsepower to drive it. When Frigidaire initially developed it they rated it as a 3 ton compressor. An engine temperature of 205F is not unusual when it's 100F ambient. Be sure that the A/C is charged correctly so the compressor is not experiencing excessive high side pressure. Be sure the compressor is not on the verge of seizing. Such a condition will drastically increase the required horsepower and will likely result in destruction of the clutch and/or drive belt. Try to maximize the vehicle's cooling system capabilities. Continue monitoring the engine's temperature. If it goes to 220-230F about your only remedy will be to turn off the A/C. Keep a high quality engine oil with sufficient zinc in the engine and use a viscosity that is appropriate for the high temperatures.

 

How did you determine the engine temp gets up to 205*? Do you have an aftermarket gauge or IR thermometer? If the AC blows cold and the cooling system of the engine is in good repair there's no need to worry.

 

Thank you all for the excellent responses! As always, knew I could count on you guys! I feel better about running with the AC now (although I'll still get a bit nervous when I see the temp gauge approach 205!).

Olds64; yes, I've installed aftermarket gauges in it. don't really like the "oops too late" lights that the car came with, need better details on how it's running.

Ozzie: Thank you for the excellent advice! I've heard some about the zinc additive in the oil, thought it was mostly for the older cars (pre-60's), but should I consider it for mine as well?

Fun71: Yeah it sure sounds like about a 50HP hit when that thing kicks on! I live in Mesa, and work in Tempe. I'm a member of the Olds Club of AZ and have been to Pavilions few times.

ClassicMuscle442: Haven't seen any sign of a solenoid for the car, but that would be a great idea to compensate when the car is idle!

Many thanks again!
james

 

Other than any mechanical issues maybe just a thorough blasting with a pressure blaster on the condesor core and radiator might help.

 

Yes; any engines with flat tappets, including yours.