I was just doing some research on SVO conversions and came across this article about the 7.3's "Deadhead" Fuel system. Can this mod be done without going to SVO? Are there any other advantages to doing it? Are there any kits out there?
"While the 1999-2003 7.3 Ford Powerstroke Diesel (PSD) was an award winning design, it had issues. Most noteworthy was Fords attempt to lower fuel tank emissions by preventing fuel which had been heated in the fuel rails from being returned to the fuel tank. This was accomplished by dead-heading the fuel in each head (fuel is fed into the fuel rail in the head, from which each injector gets its fuel, this "rail" however has no outlet).
This solution created several new problems; it caused the injectors fartherst away from the fuel inlets to be starved for fuel making them inefficient and noisy, it also allows the fuel in the fuel rail to be heated - since it is no longer flowing - causing additional injector noise and wear. In an attempt to correct the fuel starvation issue, Ford replaced the #8 injector on some engines with a different injector called the "Long Lead Injector" rather than the standard "AD" injector. The problem persisted and Ford elected to go ahead with production of the motor while continuing work on the replacement motor, the 6.0 PSD introduced in 2004.
These problems can cause poor mileage, loss of power, and noisy operation. Some of the effected trucks also exhibit a noticeable knock at idle. The audible knock that occurs under acceleration between 1500 and 2000 rpm. Engines that are knocking usually are also experiencing low power through the 1500-2000 band, poor fuel economy, and may or may not also have a knock at idle. This is because of air being drawn into the fuel system and trapped there. We repair this by adding an adjustable fuel return from the fuel rails in the cylinder heads back to the tank. The air can then be evacuated from the fuel system.
Attempting to convert this engien to VO poses problems: Since the fuel is dead-headed in the fuel rails, any fuel in the rails must be consumed in order to make room for the incomming fuel which displaces it. ie; If you are running on Diesel and wish to feed the engine VO you must run the engine long enough to consume the fuel in the rails before any VO can be burned. This is not a big issue when switching to VO, however, when switching from VO to Diesel the engine will have to be run for 15 minutes or more on Diesel before it can be shut down safely.
To avoid such long switchover times and correct the fuel starvation issue inherant in this motor, we have designed a completely new fuel system. This system takes advantage of the fact that Ford wanted to use one head casting to manufacture the heads for both sides of the engine. As a result each head has a fuel port on each end, normally one is blocked. We open these ports and feed fuel into one end of the head and out the other, so both heads are fed fuel at a rate 20psi higher than stock through a fuel selector valve, the fuel flows out the opposite end of the heads and into an adjustable fuel pressure regulator (FPR), the return from this regulator in turn flows into a valve which determines which tank to send the returned fuel to (Diesel or VO).
When switching from VO back to Diesel before shut down, the incomming diesel washes the VO from the fuel rails resulting in very fast "Purge" times. In addition this design supplies all the injectors with an equal amount of fuel making them operate quietly and providing an amazing 70 HP increase in power at the rear wheels!"
-From the Frybrid Vegetable Oil Fuel Systems