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How to Push a Junkyard 351 Windsor Past 1,000 HP! - Big-Bang 351W
We push a junkyard Windsor past 1,000 hp and to the brink of destruction.
Whenever someone utters the words, "Hey, I have an idea," it usually falls into one of two categories. Category 1 is for those inspiring, grand gestures with the strength to alter all of humanity. Simple statements like, "Let's put a man on the moon," "Let's end apartheid," or "I found the cure for cancer." Category 2 is home to those on a slightly smaller, and decidedly dumber scale—"Let's jump off the roof and use a bedsheet as a parachute," or "Let's pull this office chair behind the truck down a crowded street and get a reaction on Youtube." That sort of thing.
Thus, we came up with the idea to illustrate the strength of the stock 351W short-block by subjecting it to obscene boost levels.
The original idea was to clear up Internet myths regarding the strength of a stock Ford block and cast rotating assembly. We've all heard the stories—cast cranks, rods, and pistons will only withstand 8-, 10-, or maybe 12 psi. The fact is these components have no way of recognizing boost pressure. Actually, you might be surprised just how much power (and boost) the stock components can take before giving up the ghost. The obvious exception is the notoriously weak factory 5.0L block, but knowing this, we chose to run our boost test on the larger and stronger 351W.
The idea was simple. Take a stock 351W short-block from the wrecking yard; add heads, cam, and intake; and then start adding boost until something breaks. You might question adding the aftermarket components, but we wanted more than just big boost with our Big Bang—we wanted big power numbers to go with it. Boost multiplies the output of the normally aspirated motor, so we wanted to start with something that made more than 250 hp. This also gave us the opportunity to freshen up the junkyard jewel, since we had no idea what abuse it had endured prior to its revival.
The injected 5.8L (351W) test motor was pulled from the engine bay of an F-250 truck. The hydraulic-roller motor made life easy for us, since all we had to do was replace the cam. The motor was given a quickie ball-hone and minor surfacing to ensure good head sealing. The crank was polished and given fresh bearings, but the stock rings were cleaned and reused after increasing the ring gap to 0.035 inch.
The majority of piston destruction can be attributed to one of two issues, detonation from improper tuning, or insufficient ring gap. The extra heat generated in forced-induction applications will cause to rings to expand. The combination of excessive expansion and insufficient ring gap can cause the rings to butt together and stick momentarily in the bore. The result of this is a snapped ring land on the piston. The resulting broken piston was not due to inherent weakness (metallurgy or otherwise), but rather insufficient ring gap.
The stock short-block was reassembled using the stock cast crank, rods and pistons, then augmented with 1 2-inch ARP head studs and Fel Pro 1011-2 head gaskets. With our test mule ready, we added the first of the power producers, namely heads, cam, and intakes. Having just run the AFR 205 heads previously on our twin-turbo, carbureted 347, they were perfect for this 351W. The heads offered exceptional flow (331/235 cfm), small (58cc) combustion chambers and a 2.08/1.60 stainless valves package. The AFR heads also featured a spring package that offered sufficient rate and coil bind clearance for our sub-0.600-inch lift hydraulic-roller cam.
Crane supplied our hydraulic roller cam, but it could not be installed until we cured a piston-to-valve clearance issue. The stock dished pistons featured plenty of clearance using the factory cam and stock valve sizes in the iron heads, but the added duration and larger intake valves in the AFR heads required additional clearance. After marking the piston with clay, we used a Dremel rotary tool to notch each piston for clearance. It wasn't pretty, but our cam now had 0.060-0.070 piston-to-valve clearance.
We finished off the power producers with a TFS-R intake combo, a Holley 75mm throttle body, and 83-lb/hr injectors. Run on the engine dyno with a Holley HP EFI system and Hooker long-tube headers, the mild 351W produced 410 hp at 5,800 rpm and 406 lb-ft at 4,400 rpm.
We had just run the twin-turbo kit from CXRacing on the carbureted 347 stroker, now we applied it to the larger (but less powerful) 351W. We did, however, make a few changes to the turbo system to facilitate our test.
The first change was to replace the air-to-air intercooler with an air-to-water unit. The next change involved replacing the T-3-based GT35 turbos with larger T-4-based T76 models. This required making adapters that stepped up the T3 flanges to larger T4 flanges to accept the 76mm turbos. Capable of exceeding 700 hp each, we had more than 1,400 hp worth of turbos for the 351W.
Because we had extra wastegate springs on hand, the CXRacing wastegates were replaced by a set of Hyper-Gate 45s from Turbo Smart. We had 14-psi springs and the ability to take boost even further with a manual wastegate controller. Turbo Smart also supplied a Race Port blow-off valve. The remainder of the twin-turbo kit (tubing, couplers, and clamps) to supply the necessary boost to the awaiting 351W came from CXRacing.
Naturally, we started off slowly and worked our way up. We replaced the pump gas with 118-octane Rocket Brand race fuel and dialed back the total timing from 35 degrees to just 20 degrees. The intercooler was fed dyno water (there was more power to be had with ice water, but it is a hassle when you have to make 60-70 dyno pulls).
Starting at 7 psi, the turbo 351W produced 631 hp and 608 lb-ft of torque, while stepping up to 10.5 psi brought 719 hp and 687 lb-ft of torque. The stock crank, rods, and pistons were all still in place, so we cranked up the boost to 12.6 psi—the 5.8L pumped out 790 hp and 776 lb-ft of torque.
01. The stock dish pistons in the 351W required some minor machining to provide adequate piston-to-valve clearance. A Dremel rotary tool made short work of the cast pistons to provide the necessary clearance.
02. We replaced the stock cam with a Crane hydraulic roller. The Crane cam offered a 552/563 lift split, a 228/232 duration split, and 114-degree LSA.
03. Crane also supplied a double-roller timing chain for the 351W.
04. Since we planned on cranking up the boost, we augmented the Windsor with -inch ARP head studs and Fel Pro 1011-2 head gaskets.
05. Having had such great success on a previous 347, we installed a set of AFR 205 Renegade heads on the 351W. The AFR heads offered exceptional airflow and a thick deck to ensure sealing under boost.
06. Thanks to complete CNC-porting job, the AFR heads offered exceptional airflow, peaking at 331 cfm on the intake and 235 cfm on the exhaust.
07. The AFR heads featured a 2.08/1.60-inch stainless valves and a spring package that offered sufficient rate and coil bind clearance for our 0.560-lift Crane cam.
08. Our intake choice for the 351W was a TFS-R upper and lower. Here the lower was installed onto the awaiting long-block.
09. The TFS-R upper intake featured shorter runners to optimize power production higher in the rev range. On this application, we were not interested in low-speed power production or the better choice would have been the long-runner Track Heat or Street Burner intakes.
10. The two-bolt bottom-end was all stock, including the original rotating assembly, high-mileage oil pump, and pick-up.