Some history. I installed a 1975 Buick 455 engine and 400 trans in my 1941 Buick Super Coupe. Initially, I used the stock radiator, which seemed to work fine in street driving situations. Once I took it on the freeway, the temp would creep up to near 230 degrees and then would puke once I brought it to a stop. In the most recent Rod and Custom article, it was noted that my problem could be a stopped up radiator or that its capacity was not enough for the motor. So I took out the radiator and took it to the radiator shop to have the tanks removed and have the core inspected. As it turns out, the core was fairly clean. I then decided to exchange the stock 2 row core with a 3 row core with high efficient fins. Reinstalled the radiator and took the car for a test run in our Arizona 100 degree heat. At street speeds up to 45 MPH, the car seems to cool nicely and stayed in the 195 to 205 degree range. Took the car on the freeway and the temp goes up again to the 230 degree range within moments. Except this time, when I bring the car to a stop, it doesn't puke out the radiator overflow. Some individuals tell me if it doesn't overflow in those situations, then its not overheating. I'm not sure if that's the case, so that's why I'm posting here. Additionally, I'm running a 9 lb. cap, due to the fact that my stock tanks were only rated for 6-8 lbs to begin with. Also, we used a digital thermometer after running the car to verify the temperture guage readings and the two were fairly close to within a few degrees. Don't mean to bore you, but here's more info, since we've tried everything. The next thing we did in the process is to remove the hood, thinking we might not have enough air flow. Without the hood, we took the car out for an identical run as before to duplicate conditions. As it turns out, it did run about 10 to 15 degrees cooler, but still not where we thought it should be in the 195 to 200 range. I'll be making some adjustments in the grill area and underneath to increase the air flow. Even with that, I'll be in the 220 to 225 degree range when driving on the freeway. I need to figure out if these big block buicks tend to run hot or do I still have a combination of radiator capacity and air flow issues. Any commentary on this issue will be appreciated.
A higher pressure cap will raise the boiling point, the shop where the radiator was fixed should be able to recommend what to use. I always try to use something over 13 lbs. How about the thermostat? That's a cheap and easy item to replace and get it ruled out. If that fails, take the thermostat out and see what it does, of course as a diagnostic tool. If you know nothing about the water pump, that's also an easy item to replace. Post up a few pictures of the radiator, fan, etc. Where is the radiator's top tank in relation to the cylinder heads? Bob
In response to the last post, I changed the thermostat to a 180 from a 195. Both worked when tested outside the car. The top tank is located higher than the cylinder heads of the car. As to the water pump, if the car remains at proper temp at street speeds, why would there potentially be a problem at freeway speeds? I need to be educated on this issue.
Changing to a lower thermostat does nothing....check to make sure your mechanical advance is working.
Overheating has nothing to do with how much coolant you loose and everything to do with engine temp. 230 is too hot and you don't have to be a Buick Guru to know that. Now find your dunce cap and its to the corner with you for the next 20 minutes. I am not sure if we have enough corners for all your friends though so you'll have to take turns. OK now that I have beat you up and you have stopped reading lets sort this out. Number one the stock radiator in your '41 Buick is not going to be enough radiator to cool your 455, seems like you have addressed that problem or tried. Next are you running a T stat and if you are what temp is it? is it the cheapo T stat off the rack at "The Zone" or is it a name brand fast acting stat? Now here is one that almost everyone misses, you no doubt are running a fan shroud, but does your car have the plate that is between the grill and the radiator? Open the hood and look straight down, GM cars from the 40s all have one and forces the air to pass through the radiator and not over the top of the tank and into the engine compartment. That is what your problem sounds like. When you are toddling around town the fan makes the air pass through the radiator, when you are on the highway cooling depends on the air being forced through the radiator because of your cars forward motion.
Check the tune up on your Buick. It is amazing how many times that a simple tune will fix a hot problem. Timing is everything. Doug
Is the hot air able to get out of the engine compartment fast enough? I think beanner is on to something as well, with the incoming air flow.
If it is fine around town, but overheats at speed on the highway, you have an airflow problem. Did you get that, AIRFLOW!!!!!! Just sayin'!
Bad idea. Better to fix the problem then to ad to the problem. @ speed the electric fan will effectively block the airflow to your radiator and will do absolutely nothing to cool your engine. Fans are for cooling at low speed not for cooling at highway speed.
Thank you gents for all the comments. I'll try to respond accordingly. I do agree with the airflow concern. I will be addressing that next. I am running two 12 inch electric puller fans that are tripped by 180 degree temps. About 2700 cfm combined. The fans are part of a shroud that encompasses the whole radiator. As far as timing goes, I'm running at 12 degrees BTC per the specs for the motor. However, I have not checked the mechanical advance. Unfortunately, I don't know how, so I'll be researching how to get that task done.
take the distributor cap and rotor off and look at the springs and weights under the rotor and make sure they move freely.
Sometimes shrouds do more harm than good. Two 12" fans might be leaving a lot of covered space on the radiator, even worse if it is very shallow. Cheaper fans can be overrated too.
Is the vacuum advance hooked manifold vacuum if it does check to make sure its working.Stock clutch fan with shroud works good if there is room..1975 is an emission engine try bumping the timing and /or taking on spring off the dist so timing advances quicker.,does it have stock pulleys on in it.When we road raced corvettes in scca Showroom stock we drilled holes 1/8 to 3/16 4 to 6 holes in the t stant it helped.
Check T/A Performance, they have a high performance water pump. They claim 15-20 degree lower temps. Also I was always told that if your motor heated up at highway speeds but were ok cruising at slower speeds it was not enough radiator. Going to get one of the water pumps for the BBB in my 55' stude.
Does your lower radiator hose have a spring in it to keep it from collapsing? Highway rpm may be pulling enough suction to collapse the hose, around town the rpms vary. I'd also verify airflow, block off air paths to ensure air is flowing thru the radiator. Around town is where electric fans will help, hiway driving is airflow thru the radiator.
I'm running a '73 455 in the '35 international with the stock radiator (non pressurized) and it runs 180 at 65 mph so I don't think these big blocks are prone to running hot. I'm running similar timing and use a engine driven fan with a shroud, no fenders or hood. I too believe it is an airflow issue. Maybe shroud is shaped wrong or some funny flow coming in when on the highway?
I am suprised no one has asked is your gauge reading correct. Do you have the sending unit or bulb close to the T stat?? If its mounted on the cyl head it will read high {at least on a chevy] As most temp the unit is calibrated to read close to t stat.. I hope this helps.........
The guage seems to be correct when we used an external laser thermometer. The guage and sending unit came as a set and is located in the intake manifold.
Gents....I rechecked the timing. I was way too advanced. Brought it back to 12 BTC per stock specs and its almost purfect. Still have some airflow issues that I'll resolve
In my experience, if it overheats at low speed or idle, it's an airflow issue. If it overheats at high speed, it's a water flow problem (usually,not exclusively) Your fan, or any electric will NEVER put as much air through the radiator, as driving 60 MPH will! The couple things that might not be water flow at high speed, is air in the system, hot air not escaping the engine compartment, or head gasket or distributor issues.
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