There has been a lot to say for the cooling history of the Chev. In the beginning the 6.2 which morphed into the 6.5 was a reliable engine with mechanical fuel injection and things mostly worked well. In standard NA form the Chev runs a 76 GPH water pump, a viscous fan and a single thermostat housing. Generally the engine with this cooling system ran ok.
Once turboing came about, everything changed. The heat plume created by the extra fuel and boost mixture couldn't cycle quickly enough, and the sonic effects from the ignition under high fuel loads transmitted through the water jackets caused water cavitation on the bore walls of the water jacket. Large boiling bubbles like a pot on the stove would surround the larger portion of the upper cylinder wall and resulted in extreme problems for the upper cylinder and further upwards into the head.
There was a cooling upgrade released to cope with the problem. This consisted of a twin thermostat housing, a larger more responsive viscous fan and a larger impeller flow water pump flowing 130GPH. This didn't really solve the problem, as the problem is a design inefficiency. The Chev wasn't designed for turbo application. However there is ways to improve and effectively use this engine.
Begin with the coolant. Add heavy duty redline water wetter. This will reduce the surface tension of the coolant and effectively stop the cavitation effect on the cylinder walls in the water jacket. Nothing more to say here.
Fit the high volume water pump. Make sure it is correct for your belt fitment. There is clockwise and anticlockwise belt drives. The pump should have HO cast in the housing.
If you can run the twin thermostat housing do so, however it only works with the Stanadyne electronically controlled injector pumps as the housing fouls the mechanical injector pump accelerator linkage. Most Australian converted options are mechanical injection so not much joy there. The N/A original style thermostat housing only flows 96GPH so pay attention to the next two paragraphs, as it will address this flow problem.
Run a heater hose using a "T" from the heater supply line, fit an inline heater tap, and plumb it to the top radiator hose or tank. Run a push pull heater/bonnet type cable into the cab and open the tap whenever your temperature runs above 90C or if you anticipate running into some hard work.
Most V8 engines run identical heads. So on the Chev the coolant passage at the front is replicated at the rear with a plate covering it. Port a barb into this plate and run a coolant relief system back to the heater supply hose, fashioned using "T" joins. One for each head. The coolant will flow from the rear of the head where it's usually trapped when the heat plume from the upper cylinder walls reaches super heating temperatures and is at it's most potent. This balances the heat in the head. I use heater hose for this, soon I will run exterior copper lines instead.
When reconditioning heads, or fitting heads use a stud kit. Not withstanding the usual benefits of stud kits, there is a rear coolant passage from the block to the head that has a poorly designed badly performing gasket seal which is prone to leaking. Stud kit will solve this. I also run standard Rislone treatment constantly as the gel surface coating treats the areas prone to problems and is compatible with coolant, and not just a flush.
Correct assembly of the timing case is complicated and essential to the cooling system. Don't let hacks near your timing case. Like the TD 42 there's a number of layers for the coolant to pass through and it is perilously prone to leaking and corrosion.
Use coppermax on everything except head gaskets, as this engine was designed with poor sealing tolerances, it is commonly used by all in the USA and the military.
If I remember more ill post up here cheers
Once turboing came about, everything changed. The heat plume created by the extra fuel and boost mixture couldn't cycle quickly enough, and the sonic effects from the ignition under high fuel loads transmitted through the water jackets caused water cavitation on the bore walls of the water jacket. Large boiling bubbles like a pot on the stove would surround the larger portion of the upper cylinder wall and resulted in extreme problems for the upper cylinder and further upwards into the head.
There was a cooling upgrade released to cope with the problem. This consisted of a twin thermostat housing, a larger more responsive viscous fan and a larger impeller flow water pump flowing 130GPH. This didn't really solve the problem, as the problem is a design inefficiency. The Chev wasn't designed for turbo application. However there is ways to improve and effectively use this engine.
Begin with the coolant. Add heavy duty redline water wetter. This will reduce the surface tension of the coolant and effectively stop the cavitation effect on the cylinder walls in the water jacket. Nothing more to say here.
Fit the high volume water pump. Make sure it is correct for your belt fitment. There is clockwise and anticlockwise belt drives. The pump should have HO cast in the housing.
If you can run the twin thermostat housing do so, however it only works with the Stanadyne electronically controlled injector pumps as the housing fouls the mechanical injector pump accelerator linkage. Most Australian converted options are mechanical injection so not much joy there. The N/A original style thermostat housing only flows 96GPH so pay attention to the next two paragraphs, as it will address this flow problem.
Run a heater hose using a "T" from the heater supply line, fit an inline heater tap, and plumb it to the top radiator hose or tank. Run a push pull heater/bonnet type cable into the cab and open the tap whenever your temperature runs above 90C or if you anticipate running into some hard work.
Most V8 engines run identical heads. So on the Chev the coolant passage at the front is replicated at the rear with a plate covering it. Port a barb into this plate and run a coolant relief system back to the heater supply hose, fashioned using "T" joins. One for each head. The coolant will flow from the rear of the head where it's usually trapped when the heat plume from the upper cylinder walls reaches super heating temperatures and is at it's most potent. This balances the heat in the head. I use heater hose for this, soon I will run exterior copper lines instead.
When reconditioning heads, or fitting heads use a stud kit. Not withstanding the usual benefits of stud kits, there is a rear coolant passage from the block to the head that has a poorly designed badly performing gasket seal which is prone to leaking. Stud kit will solve this. I also run standard Rislone treatment constantly as the gel surface coating treats the areas prone to problems and is compatible with coolant, and not just a flush.
Correct assembly of the timing case is complicated and essential to the cooling system. Don't let hacks near your timing case. Like the TD 42 there's a number of layers for the coolant to pass through and it is perilously prone to leaking and corrosion.
Use coppermax on everything except head gaskets, as this engine was designed with poor sealing tolerances, it is commonly used by all in the USA and the military.
If I remember more ill post up here cheers