Avoiding Overheating

I have a new aluminum radiator, electric fan conversion and 180 degree F thermostat. From the test drives I've done, the coolant temp goes to 180 and stays consistent. So no overheating issues currently. However, I have been informed by Jerry & Lisa that my overheating issue is not fixed, and that I should start a thread to discuss this. So thank you guys in advance for helping me and anyone else who needs this prevent overheating!

Hi Jared,
Yes, in a nutshell you have an airflow issue that i've seen many times on these cars.
ALL the air going into the grill needs to pass through the radiator. When you open the hood and look at the area by the latch at the top of the radiator you can see that a huge amount of air is going over the top and not through. You lose a bunch of cooling capacity with this set up.
I can post pictures later - at least by the weekend,

Jerry & Lisa Mills wrote:Hi Jared,
Yes, in a nutshell you have an airflow issue that i've seen many times on these cars.
ALL the air going into the grill needs to pass through the radiator. When you open the hood and look at the area by the latch at the top of the radiator you can see that a huge amount of air is going over the top and not through. You lose a bunch of cooling capacity with this set up.
I can post pictures later - at least by the weekend,

ah okay, so basically, just need to manufacture a plate to fit in there and bolt into the radiator mount and perhaps the hood latch.

Agree with Jerry that a plate over the top of the rad would probably help, have one on my car and temperatures in Canada are nowhere near the ones in Florida.

If the car's temp stays steady it stays steady, and that's great. What's happened to me though is that I'd finished setting the car up and would go cruising around without ever having any temp issues, until the day where I hit total gridlock traffic on a sunny summer afternoon. The temp needle shot up within minutes and there wasn't much I could do about it except turn the car off in the middle of the lane and make everyone behind me quite angry. In my case the key to solving overheating issues has been a good shrouded radiator fan (Ford Tempos from the 90s had dual-speed fans because they overheated from the factory), and side-vents. Many old British cars have a very large grill for air to come in, but nowhere for the air to leave the engine bay so hot air just dams up. Functional louvers or side-vents also go a long way in helping the car cool down quickly once parked as well and saves your gelcoat from spider-cracking all over the hood with the temperature shifts over time.

Jared,
" a plate to fit in there  " Yes, that's it. You're not sealing up a submarine door, just make it as close as reasonably possible. Also check the sides and do the same as needed.
To expand on what David said....
" but nowhere for the air to leave the engine bay so hot air just dams up." .....is very true. For every cubic foot of air going through the radiator, 4 cubic feet comes out. Without the block-off plate at the top, and not moving with the fan on, the hot air will simply go back over the top of the radiator and form a circular air pattern and no cooling will occur. With the blocks in place, it also makes the whole system just work better and the fan won't need to cycle as often.
One of the best tools to have in your garage is "The Contemplation Stool".
After reading this, go look, and a light bulb will pop on.

I built my Sebring back in 1989 It has a ZZ3 350 Chevy. It overheated like crazy. I cut sort of kidney shaped holes in the wheel wheels and put a screen over it. The hole takes up about 1/3 of the side of the wheel wheel. Also removed the AC and removed the tube headers and put back on stock manifolds. I installed a separate trans cooler but not in front of the radiator I have a aluminum radiator with a high CFM fan. This combo works pretty well but I do little slow city driving. I t doesn't seem to overheat when I do stop and idle but I always feel that it could. I live in HOT Texas so I feel this combo is doing well. I bought a set of side louvers, oval ones made for a boat that I will put on when I find time. They're not real big, and look nice. They will let out some more engine bay heat. My mistake when building this car was getting a louvered hood and not the one with the scoop. I also use a cooling supplement in the radiator that claims it will knock down the temp 40 degrees- it doesn't, but does knock it down 5-10 degrees. Every little bit helps. Hope my experience helps a little

Another thing to look at is ignition timing.  You should be running vacuum advance on any street car that doesn't have a radical cam.  The vacuum advance should be connected to straight manifold vacuum.

I know that a lot of folks will say that it needs to be connected to ported vacuum, but trust me, ported vacuum is a relic of the very early days of smog control.  The ported vacuum retarded the timing at idle and the fuel was still burning when it entered the exhaust manifold.  The old air pumps (remember those?) injected air into the exhaust to finish the burn.  Sounds crazy, but that's the way the factories made the old engines meet the EPA standards.  It also drove under hood temps through the roof.  I have looked at a lot of pre-smog cars and almost every one had the advance connected to manifold vacuum.  Even the ones that appeared to be connected to ported were not when you traced the passages in the carb out.

If you run vacuum advance at idle, it should allow the engine to run cooler in traffic, since nearly all the fuel is being burnt in the combustion chamber.  If your car is running ported vacuum and you change it to manifold vacuum, you will need to readjust your idle speed, as it will be higher.  This is because all the idle fuel is being burnt where it should be.

I know from experience though that there are 3 sure fire ways to start an argument on an internet car site.  Talk about religion, politics or where vacuum advance should connected.

Jerry & Lisa Mills wrote:Jared,
" a plate to fit in there  " Yes, that's it. You're not sealing up a submarine door, just make it as close as reasonably possible. Also check the sides and do the same as needed.
To expand on what David said....
" but nowhere for the air to leave the engine bay so hot air just dams up." .....is very true. For every cubic foot of air going through the radiator, 4 cubic feet comes out. Without the block-off plate at the top, and not moving with the fan on, the hot air will simply go back over the top of the radiator and form a circular air pattern and no cooling will occur. With the blocks in place, it also makes the whole system just work better and the fan won't need to cycle as often.
One of the best tools to have in your garage is "The Contemplation Stool".
After reading this, go look, and a light bulb will pop on.

I was thinking about needing to go ahead and cover up the sides as well. I may try to get some measurements and 3d print the plates as my university has a 3d printer that engineering majors can use, just need to buy some filament and make a cad drawing. Your explanation makes perfect sense with the hot air essentially getting sucked back through since it has nowhere else to go.
Also love the phrase "The Contemplation Stool"! Believe me, I have spent much time at the contemplation stool already, and I 100% see what you mean.

Here's mine. Really simple. Didn't even need to make a template.
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