Cooling Engine Conversions


This summer I completed my restoration and 3.4L conversion on my MGB. I soon found this engine running hot; too hot. My water temps would reach 195 but my oil temps would keep on climbing; some times close to 250. The water temps were on the ragged edge. If I accelerated much, the water temps would begin to rise then settle back down. These temperatures kept me from taking the car very far. I would go to work, drop by a friends, head to the airport, etc. I have since kept my trips short generally under 10 miles.


This whole problem had been very troubling. I am running Evans coolant so there is no chance of boiling but I am on the ragged edge of damage. This cannot continue. I knew the radiator was sufficient. I shouldn’t be having these problems!


An interesting thing about a car on the ragged edge with its temperature is you can learn a few things.  First thing was the heater valve. It is long been said if you open the heater valve and run water through the heater coils the additional cooling would help cool the car. NOT SO!! (At least for me). When water was directed through the heater coil, my water temps rose and it was proportional to how far I opened it! What did this mean? The radiator was FAR more efficient cooling the car then the heater core.


It was also a good time to play with mixture and timing. I ran several experiments with mixture and timing. It was a good time to experiment since any real change would be visible “being on the ragged edge”.  I hooked up my EGT gauge, played with timing, mixture manifold pressure, etc. Having the Holley throttle body fuel injection made making these changes very very easy. Suffice to say nothing was gained. My main concern was something was way out of whack causing the temps to rise and nothing was; and being a car guy having a car on the “ragged edge” of cooling any real changes are going to show up.  I retuned the car based on how it should be tuned and not for the purpose of cooling. I am not going to modify the tuning to try to cool a car if something else is wrong. It is the wrong reason to change mixture or timing.


So here is what I did. First of all I needed a base line so I took the car for a spin. I drove the car in a route that took me about 7 miles. This route was mostly in the range of 40-50 miles per hour. This speed kept the engine either at high rpm in 4th or low rpm in 5th. I pulled into the drive way and the water temps were at 195 and the oil temp was 230 (and it was still climbing).


At this point I put in an oil cooler. The oil cooler was something I gave a lot of thought to. I could have put the oil cooler where the original MG oil cooler was but I really didn’t want to. First of all I had placed a bid set of air horns and I liked them there. I could have attached it to the radiator but in the back of my mind I kept thinking about the warm oil heating the air going through the radiator. It may be fine but I was looking for an alternative.


So I picked a size and mounted it under the front valance. This was out of the direct airflow but the theory was the turbulence off the valance would cool the oil cooler. This was a simple cooler which took me about an hour to mount.   

The following day I took the car for another test drive. The outside temperature was with 5 degrees of the baseline. I didn’t take the same 7mile trip, I took it TWICE! The water temps stabilized at 180 and the oil temps stabilized at 185!!!!! Hard acceleration would show maybe a 5 degree increase in temps and then drop right back to where they were!!!! Using the in car heater had NO effect on water temps!


I had a similar problem with the Pantera. Some one else put in an oil cooler before me. Problem is the oil cooler was in a stagnate air location and did little good. The location under the valance worked out better then I thought it would. I was quite skeptical at first. Now if anything I am a little on the cool side.


What are optimum oil temps? You should not be using straight water in your cooling system. “Antifreeze” added to water raises the boiling temp of the coolant. This is very intentional. As an example, in the winter time if you are outside wearing eye glasses and walk back inside the house, what happens to your glasses? They fog up. Your engine does the same thing. When it warms up it takes the water out of the air and puts it in your engine. Some people with classic cars start their engine and let it idle for 5 min once a month. This is absolutely the worst thing you can do. The engine pumps in moisture and never gets warm enough to evaporate it.  Your engine needs to be run around 195 to evaporate the moisture out. It doesn’t have to reach boiling but it needs to be close. This is why coolant moist have a higher boiling point. This is the design.


So if your engine is running hot I have to ask, do you know what your oil temps are running? An oil cooler may be just what you need. The oil cooler not only brought my oil temps down (big time!) but it made my radiator cooling so much more effective. There is no solution for adequate cooling; do not ignore the oil!