My 1977 Still Runs Hot !!!!!

[MacD2469]

Greetings to all,

I have a remanufactured engine with 1200 miles on it, after replacing the air dams, radiator seals. The engine still runs hot, the radiator itself is in good shape, and the front spoiler is new. Also I have tried changing the thermastat to a 160 degree unit, no improvement.
Prior to the new engine the freeway temperature would be 180 degrees, today it ran at 220 on a warm day in California. If I'm caught in traffic 250 degrees appears very quickly.
Would a synthetic oil lower the operating range ?

Any other suggestions would be appreciated

Something I learned the hard way ($$$$)! I did all that has been discussed here with an overheating problem exactly like this for 2 years, I tried everything... My car would run hot if I drove it more than thirty minutes at any speed. Its my daily driver back and forth to work, only 8 miles... I finally found that my timing was not returning to the basic setting at lower RPM! Basically what was happening is the timing was advanced so much at low rpm's that the fire was staying in the cylinder so long it would overheat! Imagine that! I cleaned up the distributor and the problem went away instantly. Now I check it often to make sure I don't have this problem any more.

 

[69MyWay]

This may sound dumb, but are you sure it is actually overheating?

Does it puke coolant out, and boil over with steam at 250?

The reason I ask, is right after I put the hot motor in my 90 Vette, I had a bad temp sender. It was giving me false hot readings. It took me about two weeks of testing and checking to figure it out. $5 later with a new sending unit, and no more worries.

There are several ways to test this. If you have a racing budy, they may have a laser thermal gun to shoot temps right off the upper hose or intake.

You can always put a new sensor in.

Where you get in trouble is when you use a remanufactured engine that has different size holes in the head for the sender unit. If you use the wrong kind of reducer to upsize/downsize the hole you can have the same problem. If the probe tip of the sensor touches the reducer, it will give you huge false positive over heating signals.

 

[venom94558]

I had the same problem on my 78. I put in a flex fan and I have been using synthetic oil as well. This seems to have helped with the over heating problems I was having.

 

[Blue82]

What about air under the thermostat? I have to drill a small vent hole on the outer flange of thermostats before I install them in my 82. If I don't it will intermittently overheat because the water is not touching the sensor on the bottom and the steam is not hot enough to open it.

Also, when I rebuilt my engine I had some work done at an engine exchange machine shop. The had a notice to buyers of their rebuilt GM engines to plug the water pathway on the rear passages between the intake manifold and the heads. It said that you can experience overheating if you do not install them.
I used Vortec heads and an Edlebrock intake so I followed the manufacturers advice and did not install the plugs.

Is this a possible cause and does anyone know why they want that passage blocked?

 

[MaineShark]

You should not have air anywhere in the system. If you have any significant amount of air in your cooling system, you've pinpointed your overheating problem. Bleed the air out of the system and it will probably stop overheating.

The predsure cap should prevet steam from forming.

Joe

 

[Buckskin7T7V]

Since moving to Bakersfield, ca my 77 does the same thing. I cannot keep it from getting to 220. Had the radiator cored and flushed. Installed a Stewart Stage 1 water pump. New cap and 195 thermostat. Still over heats. It is making the fuel in the fuel bowls over heat and the gas boils into the carb. Flooding. There is no room for electric fans or I would install one or two of them. Frustrating.....then again, where is there to drive in Bakersfield?

 

[AKRAY4PLAY]

check the exhaust flapper in the right manifold. mine was rusted and the flapper dropped down over the pipe. restrictive exhaust is something you may want to look into as well. with everything you have already done, that flapper and a plugged cat converter are what i would be looking at. take Chris's advice and get ahold of one of those lazer thermometers, it will make your troubleshooting much easier. Brian

 

[Buckskin7T7V]

Well I found out my A/C compressor is making all kinds of noise. None of which are "normal." I think the insides are about to come apart and this is adding a drag to the motor. Its only three years old. I switched over to the new stuff 132???? Now I need to find a good A/C guy in this small town. There are no good mechanics here.