390 overheating issues

[OzStang390]

I'm hoping someone might have some insight on why my engine overheats, it is an FE 390 GT engine with roughly 310 Miles (500 Kms) on it since full rebuild, in a 1967 Mustang which has had a full rotisserie restomod rebuild.
• Bored 30 thou. oversize (nowhere near the maximum of 60 thou).
• Block chemically cleaned.
• Head gaskets have correct orientation (indicator tab facing front of engine).
• Edelbrock alloy intake manifold.
• Edelbrock high flow waterpump (this replaced the previous new waterpump that was fitted at rebuild),
• New 180°F (82°C) high flow thermostat with correct orientation (bleed nipple at top, this replaced the previous new thermostat that was fitted at rebuild).
• New top radiator hose.
• New bottom radiator hose + spring.
• New from Scott Drake: 24" triple core copper and brass radiator (I believe the original was a 22" dual core).
• New 16lbs radiator cap instead of original 13lbs (as it now has a recovery tank instead of venting to the ground).
• Radiator pressure tested (holds pressure and pressure doesn't increase with engine running).
• Original 4V exhaust manifold minus the Pre-heater valve.
• No vacuum leaks.
• Engine is currently running rich.
• Timing was set at 10°BTDC, currently at 5° BTDC.
• Transmission oil lines go directly to seperate oil cooler (which doesn't interfere with air flow through the radiator).
• Fans tried:
°twin thermo fans,
°7 blade Ford A/C fan with viscous coupling,
°Flex fan,
°twin thermo fans (large pair from an Aussie 1998 EL Falcon).

The engine runs at a steady 183°F (84°C) when driving, but once in stop/start and idling at traffic lights the temperature climbs to 239°F (115°C) which also causes the engine oil pressure to drop at idle. Heat soak seems to be even between the engine and radiator when viewing them through an Infrared thermal imaging camera. Heatsoak across the radiator is comparatively even with no obvious cold spots. Test driving was done with and without the heater turned on, this made very little difference to the temperature.

Thank you for looking.
Cheers,
Glenn

[Keegan]

I trust that you have installed a fan shroud?

[OzStang390]

Hi Jim, yes... when we fitted the 7 blade A/C fan with viscous coupling, we used a shroud from a CobraJet. With the flex fan we used a brand new shroud from a 1970's big block, the shrouds were slightly different in shape but they both gave the same amount of cooling...

[Keegan]

Yeah thought so - but I gathered that I would state the obvious for the sake of doubt.
My next point would be the water pump. As in correct pulley/speed of operation at idle, i.e. the pump is not pulling efficiently at low revs to facilitate circulation.

[OzStang390]

We have gone from a brand new original style waterpump to a brand new Edelbrock high flow waterpump and an 82°C high flow thermostat which is definitely oriented the correct way. The waterpump pulley is the original (as far as I'm aware) with it looking like it is the same diameter as the crankshaft pulley, so it's not being under-driven or over-driven. Heatsoak between the engine and the radiator seems equal... the engine is quick to heat up and both seem to retain the heat, not dispersing it quick enough.

[Keegan]

Water pulley diameter should be 148mm.
Crank pulleys changed from 67 to 68 so you would need to confirm sizing.
I am by no means an expert or a mechanic as such but from experience I learnt a lot working on my own car.
Logic would suggest that an upgrade/improvement has had an adverse effect on another or is possibly defective. As painful as it is, revisiting the whole cooling system by confirming correct install and operation is a start. Also of importance is that each part is compatible with each other. Hence my original question about the pulley sizing.

[OzStang390]

I fully understand what you mean and I really appreciate you taking the time to ask questions just in case we missed something. While we haven't measured the diameter of the pully exactly, I have done a visual comparison of both the crankshaft pulley and the waterpump pulley and both seem to be of a very similar, if not exact same diameter to each other. I mean these cars came out of the factory with a system that worked flawlessly... and that is where we started before upgrading time after time after time. It is mentally exhausting and frustrating as I am also answering questions in a number of forums, but so far everything mentioned has already been checked by us at least twice... and components also replaced. BUT I do appreciate everyones help very much so.

[Keegan]

No problems at all. Happy to offer any input.
(The benefit of retirement is patience for me)
I will post a photo of my engine pulleys.
You will note that the water pump pulley is smaller than the crank pulley.
BTW: my Mustang is a 1968 390 GT as per factory original.
I have never had an issue with cooling in either summer, winter, highway or traffic. (Sydney summer humidity included).
I will note that upon changing/restoring original cooling parts, I did notice that after recoring the original 3 core radiator, new fan clutch, installing correct radiator cap, and running quality coolant, the engine ran cooler than it had previously.

[Keegan]

Notice that the water pump pulley is stamped “S”.

[Keegan]

Also found this. May be of interest to your situation.

[hybrid]

You'd think that the thermo fans would have solved the problem if the issue was a lack of airflow when the car is not moving.
It still may be the case I guess if the thermos were not moving enough air either.

But you've got one of two issues:

1) Not enough water flow at idle
2) Not enough airflow when the car isn't moving

Your troubleshooting steps so far seem good. I don't have any experience with aftermarket water pumps, so can't comment there. If you had room you could try a secondary thermo on the front of the radiator, but it really shouldn't be necessary with the correct setup.

Edit: It's probably also worth checking the water temp at the inlet to the radiator and the outlet. You should see a drop of around 10 degrees.
If you don't see much of a drop then either you don't have enough airflow, or the radiator isn't up to snuff. Though because it doesn't overheat when you're driving, I'd say your radiator is good enough.
If you see a good amount of drop, but the engine is still overheating you may need more water flow.

[OzStang390]

Notice that the water pump pulley is stamped “S”.

Thank you very much for this info, would you by chance have a part number for that smaller waterpump pulley?
Or know where I could buy one?

[OzStang390]

Water pulley diameter should be 148mm.
Crank pulleys changed from 67 to 68 so you would need to confirm sizing.
I am by no means an expert or a mechanic as such but from experience I learnt a lot working on my own car.
Logic would suggest that an upgrade/improvement has had an adverse effect on another or is possibly defective. As painful as it is, revisiting the whole cooling system by confirming correct install and operation is a start. Also of importance is that each part is compatible with each other. Hence my original question about the pulley sizing.

What diameter is the pulley you have (the one with the "S" marking on it), it's smaller than the 148mm you mentioned, isn't it?

[OzStang390]

You'd think that the thermo fans would have solved the problem if the issue was a lack of airflow when the car is not moving.
It still may be the case I guess if the thermos were not moving enough air either.

But you've got one of two issues:

1) Not enough water flow at idle
2) Not enough airflow when the car isn't moving

Your troubleshooting steps so far seem good. I don't have any experience with aftermarket water pumps, so can't comment there. If you had room you could try a secondary thermo on the front of the radiator, but it really shouldn't be necessary with the correct setup.

Edit: It's probably also worth checking the water temp at the inlet to the radiator and the outlet. You should see a drop of around 10 degrees.
If you don't see much of a drop then either you don't have enough airflow, or the radiator isn't up to snuff. Though because it doesn't overheat when you're driving, I'd say your radiator is good enough.
If you see a good amount of drop, but the engine is still overheating you may need more water flow.

Thank you for your input, Darryl (Nuts) and I are frustrated at not being able to sort this out, the number of changes with fans and shrouds on top of all the other changes... I even lashed out and bought an IR thermal camera. the car is so close to be ready for an engineers certificate and to be registered.... except for this damn overheating issue... so close and yet so far!

[Keegan]

Definitely 148mm diameter.
2 grooves.

You could see if Bill Upham has any at Mansfield Mustang or West Coast Classic Cougar.
http://mansfieldmustang.com/