Horse Sense: We can't remember...
Horse Sense:
We can't remember exactly when Ford Racing was officially Special Vehicle Operations, but it was a long time ago. And yet on Edelbrock's dyno mule Z347 short-block identification tag, the unit is listed as an "SVO Short-Block." The tag itself is labeled as coming from Ford Racing.
This makes sense for a semi-custom build, as the FRPP piece is assembled from just the right combination of new, high-quality hardware. Most importantly, it features the burly four-bolt Boss block, so lack of physical strength is certainly not an issue. A forged steel 3.400-inch stroke crankshaft, forged cap-screw connecting rods, and .030-inch-over forged pistons complete the no-excuses 347-cubic-inch displacement.
Key to the XT engine's big...
Key to the XT engine's big power is its RPM XT cylinder head. Extra time in the CNC machine provides better ports, while upgraded, small-stem valves and beehive valvesprings deliver maximum airflow and consistent valve events. This combination of a better valvespring; large intake valve; smallish, high-velocity port; and good in-cylinder motion brings together the latest in airflow thinking. Edelbrock says the heads made 460 hp with a small cam on a 351W, and work well on up to 408-inch-stroker Windsors.
Edelbrock added its own hydraulic roller camshaft (PN 2281). This is pretty rooty-tooty unit originally aimed at 351 Windsors that packs .573 inches of lift and 235 degrees of duration on the intake side and .582 inches of lift and 238 degrees of duration with a 112-degree lobe separation. Typical of small-block Ford cams, this dual pattern bumpstick slightly favors the exhaust and is listed as useful between 1,500 and 6,500 rpm. An Edelbrock timing chain, lifters, pushrods, and Victor Series aluminum water pump were also fitted. Oiling was mainly a Milodon affair, as they supplied the oil pan and pump. The Kendal straight 30-weight oil was fortified with Torco's zinc oil additive ZEP. It brings moly, phosphorus and zinc to the party, while the SuperFlow dyno rig provided oil filtration and cooling.
Ford is apt to put their Z304DA cylinder heads and Edelbrock's Victor Jr. single-plane carbureted intake on this short-block to form the Z347 crate engine. They rate it at 450 hp at 6,000 rpm and 400 lb-ft of torque at 4,900 rpm with a 650-cfm Holley four-barrel carburetor.The Z304DA Ford is a deep breathing cylinder head with 204cc intake ports and a 2.02 x 1.60-inch valve package, but is a notch below the Edelbrock RPM XT's specifications. This is a recently upgraded version of the popular Performer RPM casting. Edelbrock uses the XT name for it's "better" speed parts, and to make the RPM head casting into the RPM XT Edelbrock has made numerous small changes.
Ford is apt to put its Z304DA cylinder heads and Edelbrock's Victor Jr. single-plane carbureted intake on this short-block to form the Z347 crate engine. The company rates it at 450 hp at 6,000 rpm and 400 lb-ft of torque at 4,900 rpm with a 650-cfm Holley four-barrel carburetor.
Edelbrock's engine management...
Edelbrock's engine management computer fits in the small box at left; the plug-in interface at right is the Calibration Module. It allows fast, simple engine tuning with little danger of fouling things up--perfect if you were weaned on points and carburetor jets.
For starters the sparkplug is a little more advantageously placed in the XT than in Edelbrock's RPM or even the all-out Victor Jr. units says Rick Roberts, Edelbrock's Director of Engineering and designer of the XT head. The intake port is a moderate 185cc for high-velocity flow; the valve package is large at 2.02x1.57-inch to get plenty of air in and out. More importantly, the valves are upgraded, with smaller 8mm stems for improved air flow in the ports. Furthermore, the valves are lighter weight, the valve springs are beehives, and the retainers small and light so the valve events are definitely better controlled with more rpm potential.
Edelbrock has also put its considerable CNC-based manufacturing capabilities to greater use on the XT heads. "The real obvious thing to the customer is the extent to which we've qualified the key elements with CNC machining," explained Roberts. "This is all-new for Edelbrock, where we touch the ports and chamber with the CNC machine... Vic gave me a time budget [for CNC'ing time], and we met that. We can cast the ports close enough so in the non-critical areas it doesn't matter if we don't CNC machine them... so we machine only the areas that are critical and the rest is OK."