Looking for 351 Cooling Improvements.

[InjectedMach]

I'm looking to make some improvements in my cooling system. Generally speaking, it runs cool enough under most driving conditions. Only when I'm idling in traffic in the summertime, it starts to rise north of 190-200C. For context, it's a 393 build, nothing super crazy. Cooling system is pretty much stock aside from a lightly upgraded OEM style radiator with 1 or 2 added cores.
So my question is, where is my money best spent to get it to run a bit cooler? Higher flow aftermarket water pump? Aluminum radiator? Electric fans? I'm not looking to go all out and spend a bunch of money, I just need it to maintain a reasonable temp when I'm stuck idling at a light or in traffic.

Buy a 2 or 3 pass aluminum radiator from Eastwood or speedway motors then use a 2000 v6 ford Taurus fan or twin ford contour fan setup with a controller. Your oem setup is most inefficient at idle and that's when you need max airflow anything over 25 mph you can leave your fan at home.
That's a max cooling situation but I would go to electric fans and a quality controller first.

 

[Bobby]

I'm looking to make some improvements in my cooling system. Generally speaking, it runs cool enough under most driving conditions. Only when I'm idling in traffic in the summertime, it starts to rise north of 190-200C. For context, it's a 393 build, nothing super crazy. Cooling system is pretty much stock aside from a lightly upgraded OEM style radiator with 1 or 2 added cores.
So my question is, where is my money best spent to get it to run a bit cooler? Higher flow aftermarket water pump? Aluminum radiator? Electric fans? I'm not looking to go all out and spend a bunch of money, I just need it to maintain a reasonable temp when I'm stuck idling at a light or in traffic.

If you want to run cooler, get a reproduction radiator from Summit Racing or reinstall you old OEM radiator if you still have it and it is in good condition. I found out in a $900 fiasco, that the modern aluminum radiator with additional cores with the best electrical fans do not move enough air thru the radiator to properly cool the engine. I was running in excess of 215-220 Degrees F. Needless to say my A/C didn't work either. No matter what I did, it was to no avail. I ripped out all the electrical fans and radiator and purchased a new reproduction radiator made of brass and reinstalled my mechanical fan and shroud and suddenly I was running 185-190 Degrees F........and the A/C, well, it worked! Sum and total, those new radiators with additional cores don't cool additionally. They just don't push enough air thru the fins. I also have a 393C stroker build.

 

[Stanglover]

On my 71 351C 4V I use a 190 degree t stat with correct style "hat". I also installed a 3 core rad several years prior.
The upgrade I did was to install a Hayden 2710 fan clutch and a Derale 17118 fan. What is VERY important is the depth the fan is into the shroud. Mine is set with about 1" protruding out of the shroud.
Yesterday I spent almost a hour in line to enter a show in hot conditions. The temp gauge stayed at or just above 200 deg F, so not too bad. I did raise the idle speed a bit though at times to increase the flow.

 

[detritusmaximus]

The fact it gets hot when not moving, but is okay when moving is a good indicator it could be not enough air flow at idle, if everything else is good. Or not enough surface area in the radiator (higher fin count equals more surface area to radiate heat).
An option to going to electric fans, is to put one temp sensor controlled pusher fan in front of the condensor/radiator to assist with airflow at idle.

Assuming an automatic trans, what is your idle set at in drive and in park/neutral? Does it get hot in both gears or just in drive? If just in drive, a little bump in idle speed might work.

 

[Don C]

Have you verified that the temperature gauge you are using is showing the correct temperature? If not, use an infrared thermometer and check the temperature of the thermostat housing.

 

[JackinLA]

I'm looking to make some improvements in my cooling system. Generally speaking, it runs cool enough under most driving conditions. Only when I'm idling in traffic in the summertime, it starts to rise north of 190-200C. For context, it's a 393 build, nothing super crazy. Cooling system is pretty much stock aside from a lightly upgraded OEM style radiator with 1 or 2 added cores.
So my question is, where is my money best spent to get it to run a bit cooler? Higher flow aftermarket water pump? Aluminum radiator? Electric fans? I'm not looking to go all out and spend a bunch of money, I just need it to maintain a reasonable temp when I'm stuck idling at a light or in traffic.

Same issue here in South Louisiana. 71 vert with a 351W I’ve had since last Fall. Original radiator and water pump, neither in good shape. Old girl started overheating in April. Aluminum 4 row radiator, oem water pump and 180 thermostat install has her running much better.

 

[mjlan]

My experience is the same as Detritus- if the temp stays consistent when the car is moving but creeps up when stopped more than likely there is not enough air moving through the radiator to pull the heat out of the coolant.

Find ways to increase air flow at idle: are you running the correct fan and fan spacer for the shroud you have? The fan should be 2/3 of the balde width into the shroud, and have as little radial clearance to the shroud as possiblw without contacting. If that is ok you might need to add an electric fan...

 

[Hemikiller]

In the Mach, I'm running a Champion CC381 3 row radiator, factory shroud, factory non-Ac pulleys, Hayden 2710 clutch and a 69 Cougar 351W w/AC clutch fan. $5 parts store MotoRad 180° t-stat. Car idles at 900rpms, 195~200 all day, highest I've seen it climb is 205 in traffic on a 90° day.

I have the same setup on my 71 XR7, but I'm using the same Derale 18" fan that Stanglover has.

I may be switching to an electric fan in the Mach only to eliminate a potential issue with the engine revving 6500+.

 

[Spike Morelli]

If you want to run cooler, get a reproduction radiator from Summit Racing or reinstall you old OEM radiator if you still have it and it is in good condition. I found out in a $900 fiasco, that the modern aluminum radiator with additional cores with the best electrical fans do not move enough air thru the radiator to properly cool the engine. I was running in excess of 215-220 Degrees F. Needless to say my A/C didn't work either. No matter what I did, it was to no avail. I ripped out all the electrical fans and radiator and purchased a new reproduction radiator made of brass and reinstalled my mechanical fan and shroud and suddenly I was running 185-190 Degrees F........and the A/C, well, it worked! Sum and total, those new radiators with additional cores don't cool additionally. They just don't push enough air thru the fins. I also have a 393C stroker build.

I have a good friend who has a highly modified Camaro, ran into the same scenario, put in a new modern aluminum radiator ( he told me he bought it 'cause it looked so hi-tech), however didn't cool any better, actually ran hotter, so he put the heavy duty original back in and temps came back down. He also got rid of the electric fans he had installed. I probably would have as well. Sometimes electric fans become just another wiring complication, can be noisy, and to me, fans in front of the radiator, where they're seen through the grille, take away from a clean looking front view, but, some like the look.

 

[boilermaster]

Randyi00.
I am running 408 C manual trans OEM 429 radiator with correct shroud,
high quality fan and clutch and aluminum restrictor with 195 degree Windsor thermostat.
my 71 FB,s temp would climb at extended idle in 80 degree temp until I installed a 351 AC water pump pulley, which is a smaller diameter ( about 1" ) stays cooler at all driving conditions now.
rarely do I see over 200 F.
If you have a non AC car, you need to try this.
All it will cost you is a new shorter belt and the 351 AC water pump pulley.
I got mine from a 71 LTD 400 with AC. (very common part).
Boilermaster

 

[tony-muscle]

The fact it gets hot when not moving, but is okay when moving is a good indicator it could be not enough air flow at idle, if everything else is good. Or not enough surface area in the radiator (higher fin count equals more surface area to radiate heat).
An option to going to electric fans, is to put one temp sensor controlled pusher fan in front of the condensor/radiator to assist with airflow at idle.

Assuming an automatic trans, what is your idle set at in drive and in park/neutral? Does it get hot in both gears or just in drive? If just in drive, a little bump in idle speed might work.

I have the same issue described here. Shroud, spacing, sizing, fluid, thermostat. All else have checked out. I even tried the pushed fan thinking that it will help with airflow at idle but it didn't so I don't suggest this idea. Tried the wetter coolant. Been there, done that with no good results! Mine starts creeping up when in traffic only after 15-30 minutes of not moving much (think HRPT). It starts going up and once it gets to 215 then I open the hood and it stabilizes. I agree this is related to airflow. So short of opening holes in the hood to improve flow I think we need to seriously consider the idea that good 'ol copper radiators may work better than aluminum. I have a 3-Row Champion aluminum sized as big to fit where the stock one was.

 

[boilermaster]

A smaller water pump pulley will increase air flow AND coolant flow,
just saying.
Boilermaster

 

[giantpune]

A smaller water pump pulley will increase air flow AND coolant flow,
just saying.
Boilermaster

Underdrive all the things!

 

[Spike Morelli]

I thought I'd also add, that many times when overheating problem cars came into the shop, amongst all of the various things members have mentioned here, what we would always check as just part of the inspection, was to test the customer's radiator cap. The caps very often don't hold pressure as they should, even when new, which will allow coolant to boil. The protocall was to check the cap separately, and entire cooling system for pressure checking, was to pressurize to 15 pounds and must hold for 15 minutes. We did this whenever we did a water pump, t-stat, radiator hoses, anytime we disrupted the cooling system, it got the 15/15 test .

 

[Paul of MO]

My father built full out drag racing 351c's for decades. I have built several over the years and use a super simple cooling mod that actually makes 351c's actually run a little on the cool side.

Assuming radiator shroud is in place and a good radiator, fan, and water pump - OEM quality is fine.

Remove the thermostat:

Make sure the brass bypass is still installed - it is there for a reason - do not remove or block it off.

Source some thin wall .75 od pipe. We buy cheap aluminum pipe at Lowes.

Cut a short section of this pipe so that when it is inserted and bottomed out into the block below the brass restrictor it sticks up of a 1/4 to 1/2 of an inch above the hole in the restrictor.

Insert this short section of pipe into the restrictor - I have never epoxied or sealed the tube into the restrictor as it is "loose interference" as is. We have also ever so slightly squeezed the tube to make it barely out of round to make it a bit tighter but usually we just drop it in. Once everything is assembled it can not come out anyway.

Install the normal 351c thermostat that you get from any auto parts store - it will be the wrong one as no one makes the correct t-stat for a Cleveland. Even the "correct" and expensive Cleveland ones do not actually work correctly. They do not open far enough to actually enter the hole in the restrictor and block the coolant flow.

Put everything back together and see what happens.

How it works:

Without the additional tube the t-stat can not open enough to close off the bypass when completely open. The auto part store ones also have a smaller diameter tip and even if they opened enough to engage the hole in the restrictor there is still a considerable gap around the edges.

Enough coolant still bypasses the radiator that the engine runs hot.

This additional tube shortens the distance the t-stat has to open before it blocks the coolant flow through the brass restrictor. The tube also reduces the diameter of the passage so the commonly available t-stat will actually block the hole.

Once up to temp the t-stat opens and is now firmly bottomed out against the top of the added pipe. Most if not all of the coolant flow is now directed through the radiator.

This end result is that everything works as FORD designed it to.

Most cooling upgrades actually end up pushing the coolant through the radiator faster than it takes to radiate off the heat. The coolant needs to be in the radiator for a period of time to actually cool off.

We have a 71 351C, 4v closed chamber heads, 10.5 to 1 compression, fairly aggressive cam, completely stock cooling system, with the extra little pipe added.

It barely gets above the cold line even at full stop idle, in drive, with the A/C on. Just drove it on a 97 degree day and it never made it even close to the halfway mark.

Hope this helps!

- Paul

 

[Sheriff41]

My father built full out drag racing 351c's for decades. I have built several over the years and use a super simple cooling mod that actually makes 351c's actually run a little on the cool side.

Assuming radiator shroud is in place and a good radiator, fan, and water pump - OEM quality is fine.

Remove the thermostat:

Make sure the brass bypass is still installed - it is there for a reason - do not remove or block it off.

Source some thin wall .75 od pipe. We buy cheap aluminum pipe at Lowes.

Cut a short section of this pipe so that when it is inserted and bottomed out into the block below the brass restrictor it sticks up of a 1/4 to 1/2 of an inch above the hole in the restrictor.

Insert this short section of pipe into the restrictor - I have never epoxied or sealed the tube into the restrictor as it is "loose interference" as is. We have also ever so slightly squeezed the tube to make it barely out of round to make it a bit tighter but usually we just drop it in. Once everything is assembled it can not come out anyway.

Install the normal 351c thermostat that you get from any auto parts store - it will be the wrong one as no one makes the correct t-stat for a Cleveland. Even the "correct" and expensive Cleveland ones do not actually work correctly. They do not open far enough to actually enter the hole in the restrictor and block the coolant flow.

Put everything back together and see what happens.

How it works:

Without the additional tube the t-stat can not open enough to close off the bypass when completely open. The auto part store ones also have a smaller diameter tip and even if they opened enough to engage the hole in the restrictor there is still a considerable gap around the edges.

Enough coolant still bypasses the radiator that the engine runs hot.

This additional tube shortens the distance the t-stat has to open before it blocks the coolant flow through the brass restrictor. The tube also reduces the diameter of the passage so the commonly available t-stat will actually block the hole.

Once up to temp the t-stat opens and is now firmly bottomed out against the top of the added pipe. Most if not all of the coolant flow is now directed through the radiator.

This end result is that everything works as FORD designed it to.

Most cooling upgrades actually end up pushing the coolant through the radiator faster than it takes to radiate off the heat. The coolant needs to be in the radiator for a period of time to actually cool off.

We have a 71 351C, 4v closed chamber heads, 10.5 to 1 compression, fairly aggressive cam, completely stock cooling system, with the extra little pipe added.

It barely gets above the cold line even at full stop idle, in drive, with the A/C on. Just drove it on a 97 degree day and it never made it even close to the halfway mark.

Hope this helps!

- Paul

Interesting and thanks for the detailed post. I may have to look into this further.

 

[Joeaus08]

Mine was running a little warmer than I liked, never boiled over, checked about 196 degrees with my infared gun next ti the upper hose outlet.

I performed the following, I flushed my radiator (stock), replaced the radiator cap, replaced the stock 5 blade, 17" OD fan with an 6 blade, 18" OD and clutch.

All of this helped slightly, but never to my satisfaction. I ordered a high perfomance Mr. Gasket 185 degree thermostat and new thermostat housing. The first thing that was obvious was the thermostat was wrong one. It was for a windsor not a cleveland. I made that change and it dropped over 10 degrees. I can imagine that this is the problem with alot of the clevelands that overheat. Make sure the bypass washer is in the block and if not, you can get one made at a machine shop or buy them online.

 

[tony-muscle]

My father built full out drag racing 351c's for decades. I have built several over the years and use a super simple cooling mod that actually makes 351c's actually run a little on the cool side.

Assuming radiator shroud is in place and a good radiator, fan, and water pump - OEM quality is fine.

Remove the thermostat:

Make sure the brass bypass is still installed - it is there for a reason - do not remove or block it off.

Source some thin wall .75 od pipe. We buy cheap aluminum pipe at Lowes.

Cut a short section of this pipe so that when it is inserted and bottomed out into the block below the brass restrictor it sticks up of a 1/4 to 1/2 of an inch above the hole in the restrictor.

Insert this short section of pipe into the restrictor - I have never epoxied or sealed the tube into the restrictor as it is "loose interference" as is. We have also ever so slightly squeezed the tube to make it barely out of round to make it a bit tighter but usually we just drop it in. Once everything is assembled it can not come out anyway.

Install the normal 351c thermostat that you get from any auto parts store - it will be the wrong one as no one makes the correct t-stat for a Cleveland. Even the "correct" and expensive Cleveland ones do not actually work correctly. They do not open far enough to actually enter the hole in the restrictor and block the coolant flow.

Put everything back together and see what happens.

How it works:

Without the additional tube the t-stat can not open enough to close off the bypass when completely open. The auto part store ones also have a smaller diameter tip and even if they opened enough to engage the hole in the restrictor there is still a considerable gap around the edges.

Enough coolant still bypasses the radiator that the engine runs hot.

This additional tube shortens the distance the t-stat has to open before it blocks the coolant flow through the brass restrictor. The tube also reduces the diameter of the passage so the commonly available t-stat will actually block the hole.

Once up to temp the t-stat opens and is now firmly bottomed out against the top of the added pipe. Most if not all of the coolant flow is now directed through the radiator.

This end result is that everything works as FORD designed it to.

Most cooling upgrades actually end up pushing the coolant through the radiator faster than it takes to radiate off the heat. The coolant needs to be in the radiator for a period of time to actually cool off.

We have a 71 351C, 4v closed chamber heads, 10.5 to 1 compression, fairly aggressive cam, completely stock cooling system, with the extra little pipe added.

It barely gets above the cold line even at full stop idle, in drive, with the A/C on. Just drove it on a 97 degree day and it never made it even close to the halfway mark.

Hope this helps!

- Paul

Interesting. Thank you for sharing. I never paid attention to how much the "correct" thermostat (the one that TMeyer sells) opens the plug that is supposed to block coolant flow. I have a higher temp somewhere in my garage. I will dig it out and check.

 

[Randyi00]

My father built full out drag racing 351c's for decades. I have built several over the years and use a super simple cooling mod that actually makes 351c's actually run a little on the cool side.

Assuming radiator shroud is in place and a good radiator, fan, and water pump - OEM quality is fine.

Remove the thermostat:

Make sure the brass bypass is still installed - it is there for a reason - do not remove or block it off.

Source some thin wall .75 od pipe. We buy cheap aluminum pipe at Lowes.

Cut a short section of this pipe so that when it is inserted and bottomed out into the block below the brass restrictor it sticks up of a 1/4 to 1/2 of an inch above the hole in the restrictor.

Insert this short section of pipe into the restrictor - I have never epoxied or sealed the tube into the restrictor as it is "loose interference" as is. We have also ever so slightly squeezed the tube to make it barely out of round to make it a bit tighter but usually we just drop it in. Once everything is assembled it can not come out anyway.

Install the normal 351c thermostat that you get from any auto parts store - it will be the wrong one as no one makes the correct t-stat for a Cleveland. Even the "correct" and expensive Cleveland ones do not actually work correctly. They do not open far enough to actually enter the hole in the restrictor and block the coolant flow.

Put everything back together and see what happens.

How it works:

Without the additional tube the t-stat can not open enough to close off the bypass when completely open. The auto part store ones also have a smaller diameter tip and even if they opened enough to engage the hole in the restrictor there is still a considerable gap around the edges.

Enough coolant still bypasses the radiator that the engine runs hot.

This additional tube shortens the distance the t-stat has to open before it blocks the coolant flow through the brass restrictor. The tube also reduces the diameter of the passage so the commonly available t-stat will actually block the hole.

Once up to temp the t-stat opens and is now firmly bottomed out against the top of the added pipe. Most if not all of the coolant flow is now directed through the radiator.

This end result is that everything works as FORD designed it to.

Most cooling upgrades actually end up pushing the coolant through the radiator faster than it takes to radiate off the heat. The coolant needs to be in the radiator for a period of time to actually cool off.

We have a 71 351C, 4v closed chamber heads, 10.5 to 1 compression, fairly aggressive cam, completely stock cooling system, with the extra little pipe added.

It barely gets above the cold line even at full stop idle, in drive, with the A/C on. Just drove it on a 97 degree day and it never made it even close to the halfway mark.

Hope this helps!

- Paul

Hi Paul,

Thanks for this tip, it's a really interesting trick and one I can easily try.

One question though, does this not essentially do the same thing as running one of the aftermarket block off plates in place of the OEM restrictor plate? If the tube that's inserted into the OEM restrictor plate is bottomed out on the block as you described, then coolant cannot flow up through it at any point regardless of the t-stat position, right?

 

[Spike Morelli]

Most cooling upgrades actually end up pushing the coolant through the radiator faster than it takes to radiate off the heat. The coolant needs to be in the radiator for a period of time to actually cool off.

This is an important detail worthy of consideration. I've heard this many times over the years..........quality, not quantity. Most of our cars cooled just fine when new, the design is good. How many people out there have poorly maintained cooling systems, or aftermarket modifications that are compounding the problem?