I have a 1972 cutlass with a 455 in it that is overheating like crazy. I got this thing in February. Drove it once then and it got up to about 210, nothing too hot. Then I broke it down for the next few months, rewired it, redid the interior. Then I finally took it for a spin this weekend, and it very quickly went up to 260 degrees and held steady. I read through all the other forums on overheating, and am going to systematically replace/fix everything mentioned. My question is this.... I know that my vacuum system is funky. I still have the 3 main hoses attached to the "vacuum tree" on the front of the manifold, but the wire harness attached to the top looks like it had melted for one reason or another, along time ago, and when I redid the wiring, found it wasent even hooked up. The engine itself runs pretty good, but the whole vacuum thing is something I have not gotten into yet. So before I wipe out my favorite credit cards and replace every element of the cooling system, is the possible vacuum system problem a very real reason for my engine going close to supernova?

 

Indirectly maybe...
I mean if the vacuum leading to your distributor's vacuum advance is leaking and your timing never advances as the rpms climb...AND you're timing's already a bit retarded...it can cause over heating...

Retarding the timing will cause overheating is what I'm trying to say.

Ever put a timing light on it?
Does it over heat at idle?

This sounds like an interesting theory, but, I've got a feeling something else is amiss.

 

We have a '72 350 that was running hot. It was running very lean and turned out to be the carb. Lean engines run hot. Our plugs were very white which is another indicator of a lean engine. If you put your hands over the carb and try to choke it off it will actually increase in idle speed before it dies. The 3 port switch is the TCS (transmission controled spark). One thing it does is change the vacuum source to the distributor from ported to manifold vacuum (or visa versa, I can't remember right now) when the engine gets too hot. I believe the wires go to the transmission. If your running that hot I doubt this would do it unless your sucking air through a broken hose, but even then I don't think that would do it. Check to see if it is even lean before anything else.

 

Did the system have the proper amount of coolant?

Did it puke coolant out of the overflow? If not, the problem is most likely a faulty temp gauge/sending unit.

A proper tuneup, to factory specs, would be a good start.

Based on the information you've given, and assuming it is actually overheating, the vacuum advance would not be the cause.

Norm

 

Thanks for the responses. First off, the car is definetly overheating. Hooking up the factory overflow tank has been one of the few things I have actually done in the engine bay. Just idling in my driveway, with the air temp around 80 degrees, it took only about 10-15 minutes to get up to 240. I let it cool down, then took it down the street for a mile or 2, when I got back, it was steady at 260, and the overflow tank was filling up steadily till I cut the engine. I have yet to do a tuneup, but that will be one of the first things I do. One thing that I have bought but not put on yet is the missing shroud, and a new aluminum rad to replace the old one that looked like someone took it out, put it on the ground and stomped on it. Im sure both of those have something to do with it. But a good tuneup sounds like HOPEFULLY it will do the trick.

 

Check your Distributor. Was a HEI added? if so check your timing and advance against factory specs..the HEI will have a different advance unit than stock...

 

Does the car have the correct four row radiator? Is it new, or at least free flowing (I once had a radiator that was plugged in the lower half, which you could tell because the lower portion was cool to the touch). Does the car have a clutch fan and does the clutch work correctly (I've had the silicone leak out, preventing the fan from turning). Is the t-stat opening? Drop it in a pan of boiling water and watch for it to open. Are all the hoses in good shape and not collapsed or blocked internally? Is the fan belt properly tensioned and not glazed?

A stock 455 with the correct cooling system parts will not overheat like this. Start with the basics.

 

No I discovered last night that when the former owners put in the 455, they didnt upgrade the rad. So I got a new aluminum rad coming later this week. The clutch fan also felt really loose, so I got a new one of those to put in. I also got a new 165 thermo to put in also. The fan looks ok, just needs a new paintjob. Speaking of paint, when I get my new aluminum radiator, will painting it like the stocker enhance/degrade/not do anything to its cooling effectiveness? I would like to black it out to make it look stock, but not if its going to inhibit its cooling-ness

 

Also to 442scotty, no it is not YET an HEI, stock distrib. It does have the vaccuum advance hooked up to it, hopefully correctly. HEI is one of my first upgrades I am looking to do though.

 

Theoretically, flat black should reject heat more quickly. I doubt, however, that you'd be able to measure the difference.