65 Mustang overheating are high speeds

Hi,
Running a 289? See you’re running a 3-4 row aluminum radiator with an electric fan, does it seem to be more speed or RPM related?
Can you get the heat to climb by holding the RPM’s while the car’s not moving?
Distributor advance setup so you’re fully advanced at 3K? How advanced?
Solid or hydraulic Cammed motor?
You’ve burped the system, T’stat functions correctly, basic ‘s all covered?
-John
Cover on the radiator support shouldn’t make a big difference as long as airflow is not being stopped as the car’s moving. But no 2 cars act the same.lol

Higher engine RPM or higher road speed?

How hot does it get and how quickly?

At this point it's likely an issue of either airflow through the rad, water flow through the rad, or the engine dumping way too much heat into the cooling system like would be caused by a a bad mixture and/or timing. A lot of things changed at once with the engine swap and that makes troubleshooting much more difficult.

You should also go back to a 180 thermostat. The 160 is actually reducing the effectiveness of your radiator.

dvelek said:

Higher road speed .

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Hi,
SBF’s are usually pretty forgiving about staying cool if theres no motor assembly issues.. or running a high CR, wild Cam, etc..
Can you please provide a bit of info regarding its build, and if this has been an issue before, or since the motor went in?
Other information..
1) Any cross contamination, oil in coolant, coolant in oil, bubbles rising in coolant with radiator cap removed, burning coolant (sweet smell from exhaust)..HC test..
2) Timing at idle, full spark advance RPM & how much advance total?
3) Block boiled & passages clear, did a shop rebuild the block you had, or a crate motor?
4) Perimeter plastics on radiator, airflow direction of electric fan, Upper radiator support plate missing. Temp fan is set for?
5) Carbureted or TB, EFI setup...?
6) Pull a few plugs to verify one or any cylinder ‘isn’t running unusually hot, mixture correct, no detonation..
7) Nose of car slowing airflow to radiator, fan spinning in incorrect direction..CCW, or CW if standing in front of vehicle?
Have an override switch capable of turning your fan on or off at speed?
Most often it’s airflow in this scenario, if you can drive it in 2nd gear at 3K & temp doesn’t begin to spike..but in 3rd or 4th it does.
Best of luck!
-John

May sound silly but if you are running an electric fan then make sure your fan is wired to draw air towards the engine. If running the original belt driven fan then switch to high cfm electric.

Hi,
Sorry to hear. I’ll answer this better, trying to catch you before you replace coolant...
Even though this is a different block, it’s been boiled doesn’t guarantee it’s fully clean. Consider a flush so you’re certain no buildup within passages is present (as you’re now replacing coolant, only extra cost is the flush.) When draining coolant, you may see evidence of small (usually black) particulate in the catch basin if crud’s restricting passages. Just wanted to remind you of the option, to give it a shot.
Also, consider that the heater core may be partially obstructed.
If you bought a short block and installed heads, were gasket’s coolant passages to back cylinders (Tranny side)?
I’ll answer in more detail about available high CFM fans with Shrouds a bit later.
Good luck!
-John

dvelek said:

Understood John and do appreciate all your help on this.

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Hi,
Happy to help, however possible!
Gain any ground as of yet?
Noticed an A/C compressor in the pic’s posted. If there, It’s operable I’m assuming. . What is the condition of the vanes on the Condenser in front of the Radiator?(Pic’s)..
In retrospect, I’d wanted to mention a new mill was certainly your best choice. Also narrows troubleshooting.
If not newer & defect free, there’s a possibility the Condenser may be contributing to the restricted airflow when driving at speed, just wonderin’...
Run the same Condenser previously, last motor?
Realize you are both going towards diagnostic efforts yourself, respecting that, just wanted to mention you’re more than welcome to bounce a question if desired.
Running Points? Setting Dwell is important. Mech. Advance or Vacuum, or both? I TIG mechanical advances, run vacuum.. or only run Mech advance & eliminate vacuum.. easier to track. Pulling timing may drop HP, but helps in diagnostics.
Plugging Vac into the timed port on the Holley, Carter AFB’s (Edelbrock Carbs (copied them), you already know that) More for racing, helps in all scenarios.
The flex fans (solidly mounted) flatten out during higher speeds, helps higher speed air cool things when run with a shroud. Motor seems to be more sensitive than many. That radiator is more that adequate at keeping things cool.

Compressor..

Condenser..sandwiched in the middle(?)

The high CFM Fans I was speaking of with shrouding to direct airflow are relatively inexpensive, (Mishimoto). Runs (2) smaller 2,300 CFM fans (each) focusing cooling efforts on the entire surface area of the Radiator, driving or sitting, also helping equivalent flow at speed.
Your full spark timing advance timing ‘all in’ by 3,000RPM, set more conservative
by pulling timing helps narrow down things.

They make the below for near all year Pony’s, and reasonably priced, high quality
Mishimoto fan/shroud, pic’s below...
Cam Timing was set did to dot? If you have a vacuum gauge, Dwell meter, checking plug electrodes for mixture/coolant being burned, etc, all the nostalgic methods works as always did- perfectly.


Mishimoto pictured below with the Radiator and shroud. Bolt up is dead on, can use the OE threaded clips on it.

Running an auto Trans? If it’s running hot, it may increase cooling vulnerabilities.
Although I don’t really miss running the heat at full blast as temp gauges swing into the red, increasing at stoplights on a 110 degree day, sweating bullets, approaching heatstroke by the time temp levels & backs off on the gauge reflects importance on how the importance of the heater core’s role helps keep things cool. Can jump heater hoses to bypass, if
I do wish you both the best luck in nailing this, just my .02.
Please Post what you find (when possible). it may help another in the same scenario.
Running a spring on the internal coolant lines to radiator helps the effort against collapse, restrictions. No underdrive pulleys-right?
Wish you and your family safe, (ignoring our President seems to be the safest way to do that), enjoy your project!
Best of luck!
-John

dvelek said:

It’s getting up to 210-220 within 5 minutes . We are running a 180 thermostat .

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Hi!
How did you make out with your overheating at higher road speeds, all good, still fighting the good fight?
-John

had an issue like this before with overheating, timing maybe to advanced. Check that !
2. check rad cap

Noobz347 said:

This issue sounds as if it is caused by a lack of airflow.

Yes, the gap can make a difference. The lack of a shroud and the lack of having a good negative pressure area behind the radiator can also make a huge difference.

After you have closed that gap and installed a shroud, try putting a small spoiler at the base of the radiator. It only needs to be a couple of inches tall and maybe 2/3s to 3/4 of the width (although wider is better and can be the width of the nose of the car if you like).

This will increase airflow at speed and have the added side effect of making the nose less squirrely at high speed.

If you look at factory Fox cars, you will see a spoiler like the one I describe on cars from 89 to 93 and even later, from the factory.

This is one of those things that is overlooked a lot.

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think noobz hit the target here. i also think you have an issue with airflow through the rad at higher speeds. in addition to what noobz wrote, you can also open up the area where the license plate sits on the valance panel they way shelby did with his early R model GT350s, that way you get more air to the bottom part of the radiator. i plan on using the R model valance panel on my 66 coupe when i get that far.