750 Horsepower
Taking the 24-valve to the next level is where most of the differences between builders came from. Many said do a p-pump conversion while others said keep it. For us, we were conflicted.
We decided that readers who were interested in doing a p-pump conversion could re-read our 12-valve road blocks story and use the same basic outline for 750 hp. So, let's talk VP44.
The intake and exhaust systems have already been replaced. The VP pump will need to be sent
out to be converted to a Monster Pump. The Monster Pump flows enough to keep the 300 over injectors flowing at their max.
With the fuel now available, it is time to move onto air. If the vehicle is daily driven, a good compound setup with a small charger around 62 mm and a large compressor around 74 mm will provide the air from throughout the rpm range, making driving a 750 horsepower truck daily possible.
The factory intercooler isn't designed to handle this much CFM (cubic feet per minute) of air or the pressure it will be flowing at. Consequently it won't handle it very long. So upgrading to a good aftermarket intercooler is necessary. Most will support around 1200 hp while only having a minimal pressure drop between the inlet and outlet.
With the intercooler now able to support the flow, the cylinder head becomes the next restriction. Cutting the intake manifold off of the cylinder head and having an expert port and polish the head can make all of the difference. Be careful, as many people can port and polish, but few can do it as well as Dealer Machine or other companies who specialize in Cummins' cylinder heads.
While the head is off, upgrading the valve springs will help keep the pressure on the valve, which prevents the valve from floating with high boost pressures and/or rpms. In addition, adding a custom cam tuned for your particular use will help direct the exhaust out and fresh air in when you need it.
Once the air and fuel are in the cylinder, it creates a lot of pressure as it ignites. So, upgrading to a high quality head stud is a must. Some experts recommend upgrading to a 14 mm stud if you already have the motor apart, but not everyone agreed that it was needed at this horsepower level. With the head back on, a sheet metal intake manifold is used to direct the air from the intercooler back into the intake runners.