by 66e100pu Wed Apr 17, 2013 4:44 pmCooling a V-8
When it comes to keeping a V-8 swap cool, there is a lot of “seat-of-pants” advice thrown about. Some of it is sound, and some of it is, let’s just say is less than accurate. I’ve been working on not only keeping the operating temperature at a reasonable level (180 degrees), but to also ensure that the doghouse tin remains cool as well. I have tested several items that make a difference, and some that don’t. Hopefully, what I’ve found may be of value to somebody facing the same issues.
The original Ford "doghouse" design was barely adequate for the small six when the van/pickup was designed, but it is clearly inadequate in stock form for a V-8 swap. The limited space between the doghouse and the V-8 small block creates a situation where air is unable to circulate properly within the doghouse which increases the heat load to extreme levels. One solution is to expand the doghouse side panels to provide more room which many have done, or to modify the rear panel so that it vents outside into the bed area. In my case, I went with a vent, but either method will work.
There has been much debate on 2 row, 3 row, or 4 row radiators. My truck originally was fitted with a 2 row Champion aluminum radiator. It was removed and replaced with a Champion 4 row. The results, without making any other changes was the 4 row had an average temperature that was approximately 5 degrees hotter than the 2 row. Why? Because the 2 row utilizes 2 rows of 1” tubes, and the 4 row uses 4 much smaller tubes in a thicker core. The 4 row, due to the increase core thickness does not dissipate heat as effectively as the 2 row, so don’t waste your money on something that actually performs worse than the cheaper alternative. In some cases big equals better, but not with this.
Next up is the belly pan. Lots of debate on this one, but the results are very clear – don’t expect optimum cooling on a swap without one. I can assure you that Ford would not have utilized the belly pan if there was any way they could have eliminated it. It costs money to manufacture, and install. Fractions of a cent per unit are critical in manufacturing, and if they could have saved the cost, they would have. The conventional argument is that it does nothing at idle. The truth is that it does not function at idle, but it is necessary to ensure your temperature is more easily controlled at idle. The belly pan is needed to direct air flow throw the radiator, and subsequently provide circulation through the doghouse. Without the pan, the airflow hits the very bottom of the radiator and provides almost no positive circulation inside the doghouse. The key to controlling the temperature is minimizing heat load. The engine is a heat generator, the harder you push it, the more heat it generates. The least amount of heat generated is at idle. The belly pan is critical in minimizing heat load while driving so that when you are stuck for long periods at idle, the cooling system has much less to deal with to maintain a reasonable temperature. I found that running without a pan increased the coolant temperature by 10-15 degrees while running down the road. At idle, without any airflow the engine temperature would start to creep up slowly, and eventually go to about 210 degrees which is far too hot. With the pan installed, the engine temperature stays at the 170-180 level while running down the road, and when stopped, the temperature will drop to 165 degrees even if left idling for hours. Why? Because the cooling system is far less taxed in trying to maintain temperatures in the 170-180 range than it is trying to bring 195-200 degrees down to a reasonable level which is more difficult, if not impossible for it to do.
The next item was to install a fan controlled remote transmission cooler. Conventional wisdom says that removing the transmission fluid for the radiator will reduce the heat load. Sounds like it makes sense, but does it matter. I found no difference in coolant temperature either way. The reason I went with the external cooler was to eliminate the possibility of ruining the transmission from water contamination in the event that the cheap cooler Champion uses in the radiators ever let go. If you think about the actual volume of fluid the integral cooler can hold, it is very unlikely that it will affect coolant temperature. It is much more likely that the inadequate integral cooler will not provide sufficient cooling for your transmission than to think the cooler is introducing an enormous amount of heat into your radiator. Even under extreme conditions, the integral cooler only holds about a 1/2 quart of fluid which would have to get beyond hot to alter the coolant temperature in the radiator by any appreciable amount. I’m a big fan of external coolers, but not to reduce heat load in the doghouse. Again, moving to an external cooler resulted in a zero reduction in operating temperature.
High volume water pumps are another popular item. Been there, done that, and to be honest their effect on cooling over a good quality stock pump is again, zero. Save your money for a more worthwhile modification.
Cooling fans – what works, what doesn’t? This one is easy, a stock 6 blade fan, or a flex fan, or any mechanical fan WILL NOT cool a V-8. Electric fans with a rating below 3500 cfm WILL NOT get it done either. There are some very high quality 3600 cfm units available new, and the Taurus fan conversions will work too. Running a mechanical fan, as well as an electric unit will decrease the electric fans effectiveness. Because of the limited space inside the doghouse, the mechanical fan disrupts the airflow exhausting from the electric fan and decreases its effectiveness – been there and tried that too. It is best not to cut corners on the fan controller. I use an electronic Derale unit with a temperature probe that is threaded into the thermostat housing, it is more accurate than the expansion bulb that inserts between the radiator fins.. The key is to accurately set the “on” temperature to about 5 degrees below your desired “run” temperature. If you want to run all day at 180 degrees, set the fan to come on at 175. Always make it easy for the system to pull the temperature down from a reasonable level – waiting for it to get hot and then expect to pull it down easily is almost always asking too much. What about letting the cooling fan run with the ignition off? Sounds good, but does little in practice. Running your fans without coolant circulation will only cool the coolant in the radiator, not the coolant in your block. The engine itself cools at the same rate with or without the fan running at shutdown. It does help to purge hot air in the doghouse eventually, but that occurs after running long enough to draw the heat load off the hot radiator. In practice, the difference is so minor that it for me it wasn’t worth the battery drain, so I changed back to fans “off” on shutdown.
Thermostats – what should I use? I’ve found that 160 works best. Why? Because the thermostat opens to full circulation at whatever temperature unit you choose. Doesn’t mean the engine will stay at that temperature, just when your coolant is fully circulating. So in keeping with the theory that it is easier to bring down a temperature that is reasonable rather than one that is hot, then why would you delay circulation until 180, 185, or 190 degrees? If you want to stay in the 170-180 range, use a 160 thermostat.
Engine timing is the culprit of many overheating problems. It is also responsible for bad MPG. Timing MUST be set with a vacuum gauge, and there already more than one post on how to do this if you are not familiar with the procedure.
Other items you need to check if you have a new build, or just bought the vehicle:
Make sure block passages are not blocked with sludge or casting remnants.
No vacuum leaks
Head gaskets are not installed “backwards” or blown.
Lower (suction side) radiator hose has a spring installed to prevent collapse.
Adequate fan shroud is in place IF the electric fan does not cover at least 90% of the fin area alone.
So, in a nutshell, what has worked the best after testing a variety of combinations:
2 row Aluminum Radiator
Stock steel impeller water pump
160 degree thermostat
3600 cfm electric fan with temperature probe in thermostat housing
Timing at maximum advance without detonation
Stock belly pan
Adequately vented doghouse
Barring any vacuum leaks, head gasket problems, coolant passage blockage, or some other catastrophic condition, this should have your V-8 conversion running at 180 degrees or below even when the outside temperatures are boiling.
Hope this helps!
When it comes to keeping a V-8 swap cool, there is a lot of “seat-of-pants” advice thrown about. Some of it is sound, and some of it is, let’s just say is less than accurate. I’ve been working on not only keeping the operating temperature at a reasonable level (180 degrees), but to also ensure that the doghouse tin remains cool as well. I have tested several items that make a difference, and some that don’t. Hopefully, what I’ve found may be of value to somebody facing the same issues.
The original Ford "doghouse" design was barely adequate for the small six when the van/pickup was designed, but it is clearly inadequate in stock form for a V-8 swap. The limited space between the doghouse and the V-8 small block creates a situation where air is unable to circulate properly within the doghouse which increases the heat load to extreme levels. One solution is to expand the doghouse side panels to provide more room which many have done, or to modify the rear panel so that it vents outside into the bed area. In my case, I went with a vent, but either method will work.
There has been much debate on 2 row, 3 row, or 4 row radiators. My truck originally was fitted with a 2 row Champion aluminum radiator. It was removed and replaced with a Champion 4 row. The results, without making any other changes was the 4 row had an average temperature that was approximately 5 degrees hotter than the 2 row. Why? Because the 2 row utilizes 2 rows of 1” tubes, and the 4 row uses 4 much smaller tubes in a thicker core. The 4 row, due to the increase core thickness does not dissipate heat as effectively as the 2 row, so don’t waste your money on something that actually performs worse than the cheaper alternative. In some cases big equals better, but not with this.
Next up is the belly pan. Lots of debate on this one, but the results are very clear – don’t expect optimum cooling on a swap without one. I can assure you that Ford would not have utilized the belly pan if there was any way they could have eliminated it. It costs money to manufacture, and install. Fractions of a cent per unit are critical in manufacturing, and if they could have saved the cost, they would have. The conventional argument is that it does nothing at idle. The truth is that it does not function at idle, but it is necessary to ensure your temperature is more easily controlled at idle. The belly pan is needed to direct air flow throw the radiator, and subsequently provide circulation through the doghouse. Without the pan, the airflow hits the very bottom of the radiator and provides almost no positive circulation inside the doghouse. The key to controlling the temperature is minimizing heat load. The engine is a heat generator, the harder you push it, the more heat it generates. The least amount of heat generated is at idle. The belly pan is critical in minimizing heat load while driving so that when you are stuck for long periods at idle, the cooling system has much less to deal with to maintain a reasonable temperature. I found that running without a pan increased the coolant temperature by 10-15 degrees while running down the road. At idle, without any airflow the engine temperature would start to creep up slowly, and eventually go to about 210 degrees which is far too hot. With the pan installed, the engine temperature stays at the 170-180 level while running down the road, and when stopped, the temperature will drop to 165 degrees even if left idling for hours. Why? Because the cooling system is far less taxed in trying to maintain temperatures in the 170-180 range than it is trying to bring 195-200 degrees down to a reasonable level which is more difficult, if not impossible for it to do.
The next item was to install a fan controlled remote transmission cooler. Conventional wisdom says that removing the transmission fluid for the radiator will reduce the heat load. Sounds like it makes sense, but does it matter. I found no difference in coolant temperature either way. The reason I went with the external cooler was to eliminate the possibility of ruining the transmission from water contamination in the event that the cheap cooler Champion uses in the radiators ever let go. If you think about the actual volume of fluid the integral cooler can hold, it is very unlikely that it will affect coolant temperature. It is much more likely that the inadequate integral cooler will not provide sufficient cooling for your transmission than to think the cooler is introducing an enormous amount of heat into your radiator. Even under extreme conditions, the integral cooler only holds about a 1/2 quart of fluid which would have to get beyond hot to alter the coolant temperature in the radiator by any appreciable amount. I’m a big fan of external coolers, but not to reduce heat load in the doghouse. Again, moving to an external cooler resulted in a zero reduction in operating temperature.
High volume water pumps are another popular item. Been there, done that, and to be honest their effect on cooling over a good quality stock pump is again, zero. Save your money for a more worthwhile modification.
Cooling fans – what works, what doesn’t? This one is easy, a stock 6 blade fan, or a flex fan, or any mechanical fan WILL NOT cool a V-8. Electric fans with a rating below 3500 cfm WILL NOT get it done either. There are some very high quality 3600 cfm units available new, and the Taurus fan conversions will work too. Running a mechanical fan, as well as an electric unit will decrease the electric fans effectiveness. Because of the limited space inside the doghouse, the mechanical fan disrupts the airflow exhausting from the electric fan and decreases its effectiveness – been there and tried that too. It is best not to cut corners on the fan controller. I use an electronic Derale unit with a temperature probe that is threaded into the thermostat housing, it is more accurate than the expansion bulb that inserts between the radiator fins.. The key is to accurately set the “on” temperature to about 5 degrees below your desired “run” temperature. If you want to run all day at 180 degrees, set the fan to come on at 175. Always make it easy for the system to pull the temperature down from a reasonable level – waiting for it to get hot and then expect to pull it down easily is almost always asking too much. What about letting the cooling fan run with the ignition off? Sounds good, but does little in practice. Running your fans without coolant circulation will only cool the coolant in the radiator, not the coolant in your block. The engine itself cools at the same rate with or without the fan running at shutdown. It does help to purge hot air in the doghouse eventually, but that occurs after running long enough to draw the heat load off the hot radiator. In practice, the difference is so minor that it for me it wasn’t worth the battery drain, so I changed back to fans “off” on shutdown.
Thermostats – what should I use? I’ve found that 160 works best. Why? Because the thermostat opens to full circulation at whatever temperature unit you choose. Doesn’t mean the engine will stay at that temperature, just when your coolant is fully circulating. So in keeping with the theory that it is easier to bring down a temperature that is reasonable rather than one that is hot, then why would you delay circulation until 180, 185, or 190 degrees? If you want to stay in the 170-180 range, use a 160 thermostat.
Engine timing is the culprit of many overheating problems. It is also responsible for bad MPG. Timing MUST be set with a vacuum gauge, and there already more than one post on how to do this if you are not familiar with the procedure.
Other items you need to check if you have a new build, or just bought the vehicle:
Make sure block passages are not blocked with sludge or casting remnants.
No vacuum leaks
Head gaskets are not installed “backwards” or blown.
Lower (suction side) radiator hose has a spring installed to prevent collapse.
Adequate fan shroud is in place IF the electric fan does not cover at least 90% of the fin area alone.
So, in a nutshell, what has worked the best after testing a variety of combinations:
2 row Aluminum Radiator
Stock steel impeller water pump
160 degree thermostat
3600 cfm electric fan with temperature probe in thermostat housing
Timing at maximum advance without detonation
Stock belly pan
Adequately vented doghouse
Barring any vacuum leaks, head gasket problems, coolant passage blockage, or some other catastrophic condition, this should have your V-8 conversion running at 180 degrees or below even when the outside temperatures are boiling.
Hope this helps!
I totally agree- yet will add = the water in the radiator for the tranny cooling (auto) removes the heat faster than any air type cooler can / will! I will also add that now days teh best solution for added cooling is to have a fan shroud made if none is present!! That alone will aid greatly when stopped in traffic. I know as ive made several in past years.Happy Vannin!!
