It has been driving me crazy since I finished the car 3 yrs. ago. It is an original engine 250hp., 327, in a '62. The engine was overhauled to bone stock and the radiator replaced with a Dewitt's. Of course the block was hot tanked and cleaned out as were the heads. The original water pump was sent in and restored. Distributor was also. Spark plugs read good. It just wants to run warm according to the the gauge, so I bought a infrared temp. unit to check it against the car gauge and they hold the same approx. temp. The temp will climb to near 220º when traveling through a town but will drop only about 5º when you get in the country traveling a steady 55 mph. It has never boiled over, but I do not like to see the temp. up in that range. I was thinking about it today and I remember my friend who was helping me suggested that a small hole be drilled in the thermostat as a way to prevent a stuck thermostat. A hole was drilled in the thermostat for that reason.Now I am wondering if that hole, which is around 1/8" or a little more, is what is causing this temperature. All things else on the car check out OK, as far as tune. Any ideas? Could this thermostat be causing that?

 

How many miles on the rebuild? What is the jetting? Could be running lean, if so, that will contribute to the problem. What are your timing specs? When you filled the cooling did you do it through the thermostst housing? Temp readings should be accurate, not approximate. Dennis

 

Dave, is the timing set correct? Did you IR the upper and lower radiator hoses, as well as the thermostat when it gets up to temp? Sometimes air gets trapped when you refill. Is the expansion tank filled to half full? Does it stay that way after a run? Is the thermostat right side up? Since the block was flushed it should be okay. I flushed mine on the car by pulling both drain plugs on the side of the block just above the oiol pan. I refilled the block thru the thermostat hole and then put the thermostat back in. Is all the fan shroud there. I have seen cars with it missing. I also had the temp gauge recalibrated on one of mine. Others will chime in.

John F

 

becase it dont boil over you may have a bad sender or it's not grounded good

 

Unless the thermostat is stuck closed, it would not cause this. You can confirm (you have a 180* thermostat right?) it's operation by placing it in a pot and heating the water with a thermometer in there and observing it's operation a couple of times.

If it's OK and the radiator is new, what about timing, and the fan shroud, seals, and clutch fan?? Pilot Dan

 

Drilling a small hole in the thermostat has been done for years to help purge air out of the system, it works and does not hurt at all unless the hole somehow damaged the normal operation of the thermostat. Rule this out with a new thermostat but I would drill the new one, trapped air can cause hot spots in the block.
Verify actual block temp with an infra red heat temp tool.
Timing issues stated in previous posts are a very valid possibility.

 

The engine now has close to 2500 miles on it. The carb is the original WCFB that I sent to R.D. Katter to restore. I do not know what the jetting is, he may though. When I say approx. on the temp. I didn't want to confuse the gauge with IR. The IR gives a number and the gauge in the dash really doesn't.It just gives an area range of temp.I took the IR temp. off of the temp. sending unit are in the intake manifold. The clutch fan is new. The fan shroud shroud is complete and is NOS. I had bought it back in the 70's, through my Chevy dealer. There are no seals around the radiator on a 250hp. Timing is by the book, I am running points and of course the dwell is at 30º. The fan clutch is new. I have tried several old temp. senders I removed from GM cars that were of late 50's-early 60's manufacture and I watched the stampings on them so that they matched what an article in the "Restorer" said they should be. They match the readings and marks on the original sending unit. I tried several and they all read the same or so vary close to the same. I guess when the weather gets better, I will start all over and recheck all that was mentioned here. I was hoping the drilled thermostat, would be the answer. I tried several of those also. With the 180º thermostat and the engine warmed up, it will read on IR right in the 215 area give or take a couple degrees. Thanks for the responses.

 

Somebody said the replacement fan clutches don't lock up until a much higher temperature than the originals.

Don't know, I still have the old ones.

 

I tried and used the original clutch fan to start with. Then to eliminate the fan clutch idea, I bought a new one. It made no difference in the engine temp.

 

Good point, and they also make a clutch fan eliminator which allows the fan to turn at full engine speed all the time. One other thought, You did not plug the cooling passages in the intake by mistake did you??

 

What Fan blade do you have, 5 blade, 6 blade or 7 blade.
When the car is hot and overheating is the fan roaring and pulling a lot of air.
I think Mike M has stated many times that it should pull enough air to blow your hat off if you rev the engine with it engaged, this is pretty accurate. An engaged fan clutch should turn the fan close to 90% of engine speed, if you rev it to 3500 rpm it should blow a ton of air. It is possible to mount the fan blade backwards, this should be ruled out.
It is possible to upgrade to a better fan blade that pulls more air.
Maybe your waterpump impeller is not adequate. Some pumps are more of a positive displacement pump than others. The simple paddle wheel impellers are not that good but are on many cheap rebuilds today. Just some idea's hopefully new ground to cover.

 

Vacuum advance unit working correctly and connected to a constant vacuum source?

Jim

 

I have the exact size and engine year you have. What I did was pull the engine, remove heads and oil pan, block the water pump inlet hole with a plate and put acid in the block up to the top and set overnight. Took to car wash and blasted out the water jackets with the power sprayer. All kinds of crap came out. Did the heads the same way. I purchase a 160 degree high flow theromstate. It was modified by drilling (3) 1/8" holes equally spaced. Did not get engine back together till nov so I do not know about summer heat but now it never gets above 160 degrees. Of course it's winter now so it should run cooler. You said 250 HP did not have radiator seals to block air. I'm sure you are refering to something else and not the 3 piece rubber seal that fits at the bottom of the radiator. I've made up my mind that if it runs hot this summer, I plan on having a dirct drive to the fan and get a fan with more blades.

 

Run it without the thermostat to rule it out.

 

Well now you can see why I am stumped. Bill Mock rebuilt the original water pump, I assumed he would have changed the impeller if needed. Bill Clupper rebuilt the original distributor. Fan blade is the original 5 blade fan that it came with from Chevrolet. Though for the heck of it I did change to a NORS 5 blade, just to check, since I had one to try. The fan appears to be the same, but the rivets holding fan blades on are a little different than the production line fan. Other than that, I could not see a difference. Brakes are new and there is all new lines and rebuilt cylinders, they are also manually adjusted, just short of touching the drums. I can easily push the car by hand in the garage.

In reference to Moxie62, the engine will get this high temp reading when it is over 80º. Below that, it runs up to 190º-200º. I know they ran the rubber strips on the solid lifter motors and maybe even the 300hp. motors, but not on the 250hp.

An engine re-builder in Lima, Ohio did the machine work and assembled the motor. Bores were just touched up. Rings replaced and all new bearings, original heads now have hardened seats.They came highly recommended from many sources. So I am clueless if they would have plugged the cooling passages in the intake.

Engine will cool down when up to highway speeds, but cruising around the lake or in town at 30mph, will get you concerned in about 20min. about the temp. Actually, it does act as if the thermostat is stuck open. Now with all the questions. If I cruise at around 30-40mph to a neighboring town about 12 miles away, the temp. will just keep building slowly.

My experience on no thermostats was when I had trouble with a different car a radiator man gave me some advice that has worked correctly for me. He stated that a thermostat is constantly opening and closing to maintain the temp. evenly in the engine. If it is removed, the coolant just flushes around without really getting a chance to stop in the radiator for the air to cool it. On a trip that I was having overheating going on in another car, he fixed the hole the radiator, created by a car in front that kicked up a rock, thus making it so we needed a radiator shop and he put in a thermostat and we never had trouble again. So since then, it made sense to me.

I think when spring gets here, I will replace the thermostat again and see what happens.

 

Thats correct. They can be re-clocked by turning the coil spring counter clockwise 180 degrees.

New ones are set to activate in the 210 range.

Mines a '63, standard cooling with a clocked clutch fan. When it's 80 degrees outside it stays at 180 or below.

 

If running at highway speed doesn't drop the coolant temp significantly, then that eliminates the fan clutch as the culprit. You should be aiming the infrared beam at the upper radiator hose where it joins the thermostat housing as aiming at a reflective (silver) surface will cause false/low readings.
Your ignition timing should be about 6 degrees advance at idle with vac advance disconnected. Total static plus centrifugal should be about 36-38 degrees, and total plus vacuum advance should be about 52 degrees, which is where it will be running while cruising on the highway. You should also remove the tstat temporarily, as a test, although I doubt that the tstat is your problem. Check the lower radiator hose is being held open with the internal spring and not collapsing. Chack that the heat riser is operating correctly or, better yet, wire it wide open. Check your spark plugs for a lean condition...........the insulators should be tan to brown, not white and not black. The pump impeller is a "stretch", although possible but not probable.

 

Even 250 horse had the three seals--one at each lower corner and the strip across the bottom. Only 340 and360 had the side seals.

 

I better reclock the clutch fan. Of course I well recheck all the timing and other settings as well. Timing was set at 6º, but that was a few miles ago. I need to check the seals also, because I just don't remember. I do know that the spark plugs in my eyes looked perfect, in color, as it was one of the first things I checked. One reason I checked them first is because I had dated spark plug wires on and they went in the trash after about 300 miles. I checked the plugs then to see where the miss was coming from.

Thanks for all the tips, I have something to look for.

 

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