Tom Wilson
November 1, 2009
Photos By: Edelbrock Corp.

Edelbrock is so busy building new Ford parts we're taking a look at a whole assembly of them this month. By that we mean a 347 crate engine boasting a complete lineup of Edelbrock gear--including XT cylinder heads, XT electronics, and a spanking-new XT intake manifold. While Edelbrock builds just about everything that makes horsepower from intake gaskets to exhaust pipes, but the company's Ford lineup has yet to add a cylinder block, crankshaft or pistons. As such, it made sense for Edelbrock to start its engine program with an FRPP short-block, the M-6009-Z347.

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.

Like many enthusiasts with a few boxes of usable engine parts already in the garage, Edelbrock wanted to use its own camshaft, heads, intake, etc., so what isn't in the Z347 short-block is also important. That's mainly the camshaft and timing chain, but you'll also want an oil pump, pickup, oil pan, and front timing cover, not to mention everything north of the block's decks.

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.

The Z304DA Ford is a deep-breathing cylinder head with 204cc intake ports and a 2.02 by 1.60-inch valve package, but it's 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 its "better" speed parts, and to make the RPM head casting into the RPM XT Edelbrock has made numerous small changes.

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."

Roberts recalls the XT head flowing about 270 cfm at .600-inch lift, with a peak exhaust flow of maybe 220 cfm. Perhaps more importantly, "It's not just peak numbers, the valve job is better than before. We put four or five angles on the intake, two and a radius on the exhaust; it's a more modern valve job," says Roberts. In other words, the mid-lift flow are substantially better than the Performer RPM cylinder head. Or, as Roberts added, "It takes a flat-tappet cam and makes it look like a roller, and makes a roller just that much better."

Maybe more than most parts makers because Edelbrock has such large manufacturing capacity, "This is a little new for us, this level of head prep. We can put the port in CAD, and then send it to the shop as opposed to making a detailed hand-made port and then trying to make a tool path from that. It worked, in this case, really well," said Roberts.

The better valves and conical springs did add a little more cost to the XT head. "We thought of [using] 11/32-in. stem valves and knocking $100 off of it, but people are recognizing the value of this stuff, so we went with the real parts," noted Roberts. And it seems to work. "We wanted to see 10 hp over the RPM heads, and got more like 15 horsepower in a straight head swap. And that's still with a 60cc chamber, so we didn't make power with the compression."

Like the heads, there are a lot of trick details to the fuel injection as well. We don't have the space to get too deeply into the Edelbrock XT electronics packages, but let's start by saying there are various levels available. Scott Armish, Edelbrock's Electronics Engineer explained some are simple enough for us Average Joes, others offer the full gamut of tuning, data acquisition, high- and low-impedance injector support and other niceties expected in a top-flight electronics suite such as those in pro racing. And that's no surprise when you hear Edelbrock has teamed with EFI Technology--a name more commonly associated with Indy car electronics--to produce the XT electronics package.

Because the XT intake manifold we're examining here is a carburetor replacement piece, it is packaged with a relatively basic XT electronics kit that includes a small ECU with an accessible calibration selection guide. The ECU, "comes loaded with a calibration, of course, along with a manual with a tune-up list. These show the hardware combination that tune was made up with," says Scott. "There is also a primer on what affects what, then you can use the little tuning section to help you learn how to tune."

"Once you've mastered playing with those, then you are ready for the Calibration Module," says Scott. This compact module plugs into the XT system and lets the owner, "enter the system at either the Fuel or Spark modes. There are six rpm, four vacuum, and four spark setting Break Points," he explained. "You can bump the idle up and down, change the rev limiter, turn closed-loop on or off for the fuel control... It's just enough adjustability for the average guy." The system is more adjustable than the old standard of sending chips back and forth in the mail, which is what Edelbrock's older Pro-Flow required.

When Edelbrock eventually releases its own Ford crate engines, this is the XT electronics level they'll be supplied with. It seems to offer a useful level of tuning without being overly complex, plus, the Calibration Module is also a display module, so it allows viewing rpm, vacuum and so on. That could be handy for a guy updating an older carbureted Fox Mustang, let's say, as the XT electronics would deliver electronic engine management plus some "instrumentation" to keep an eye on things without having to rewire the car.

For more advanced hot rodders there is the standalone XT Plus. It forgoes the Calibration Module, going straight to a laptop interface. "It's the next to highest [XT] application, comparable to a FAST XFI," says Scott. XT Plus is in the $2,500 to $3,000 retail range. This is just the electronics, with no manifold. Above the XT Plus is the upcoming XTR. "This is a racing system, again from EFI Technologies," Scott added. "It's a full-blown mil-spec, low-impedence injectors, all-out unit." This is a notable step up from Edelbrock's more typical bolt-on and affordable racing orbit and we take that as an indicator of the increased reach this large company will need to prevail in the changing performance aftermarket.

Not for sale but fun to examine was a trick little engine emulator Armish was working on. It was an unboxed circuit board well populated with electronics and some blinking LEDs during our visit; it simulates an engine for the XT electronics to "run." It will be used for training and troubleshooting by Edelbrock-schooled technicians.

The brand-new hardware on the crate motor dyno mule we're checking out here is the Pro Flow XT intake manifold. Designed by Brent McCarthy, Edelbrock's Chief Engineer of Research and Development, the XT is a short-runner, tunnel-ram like intake designed as a carburetor replacement part. Early Mustangs, all they way up to 1985 Foxes ran carburetors and are prime candidates for this intake-based conversion. Of course, it could be fitted to later EFI Mustangs, but it makes no economic sense as the XT intake is sold with its own XT electronics package, so you'd be paying to replace your existing Ford electronics.

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On The Dyno
We did watch the XT engine, heads, cam, intake, and throttle body during prototype runs on one of Edelbrock's three in-house engine dynos. Initially there was the usual monkeying around with ignition timing and XT electronic mapping as the XT intake was tuned for maximum power.

The baseline the XT was running against was the single-plane Pro Flow II. The Pro Flow II had put up nice numbers with 486 hp and 432 lb-ft of torque maximums, while the XT just matched the horsepower at 485 hp at the 6,500 rpm peak, along with better torque at 439 lb ft at 4,700 rpm.

Frankly, no one was overly excited by the XT's power output compared to the Pro Flow II, so McCarthy took matters into the grinding booth. There he introduced the XT's fuel-injector bosses to the die grinder, hand-whittling them down to about half their generous as-cast size. This didn't surprise us as peering into the runners showed the seemingly overly large bosses were at the runner's base, right where the air is passing into the cylinder head's ports.

Hand-detailing the injector bosses was the right move, the power moving up to exactly 500 hp and the torque peaking at 445 lb-ft. That is a healthy 347 stroker in a sporty, rev-happy package. Looking at the bottom of the dyno sheets, we find the XT engine opens at 2,500 rpm with 335 lb-ft of torque, so it isn't hopelessly soggy down low like your dad's carbureted tunnel rams. The torque curve does make a notably steep jump between 4,000 and 4,500 rpm, however. Torque swells from 381 to 440 lb-ft in that range, with power ramping from 290 to 377 in the same span.

Edelbrock's XT testing reported in this article was done at a cooling water temperature of 172 degrees using a standard correction factor, plus a step (not a sweep) test and the air/fuel ratio was fully leaned at 12.7 to 13.0:1 at the power peak. These parameters will give a slightly higher, say 5 to 7 hp, reading than a sweep test, SAE correction factor, and slightly richer mixture.

Also interesting, Edelbrock uses a long tube to organize the airflow into the throttle body. They call it Old Faithful, as it seems to help power and repeatability a little. It did give a place to mount an air meter on an EFI engine, so we can accurately report air consumption was 655 cfm at 500 hp.

Part of the dyno work done during our visit was crate-engine calibration by Troy Hooker. He was operating the dyno engine with the XT Plus electronics with laptop interface, a system he really likes. He characterized the system as offering plenty of adjustability without drive-you-nuts detail, and pointed out that the system's ability to read on the fly and flash download to the XT box is a speedy help. He also gave us a quick XT Plus tour, demonstrating the tiltable maps and table-viewing options for fuel and spark, plus an encyclopedic data-logging capability.

It clearly offers comprehensive tuning and a variety of viewing options to make sense of what can be an arcane adjusting process.


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The XT intake is also tuned for an aggressive mid- and good top-end rpm range. Its shorter runners cannot deliver the low-range torque a big dual-plane carbureted intake or long runner EFI intakes such as the Performer RPM II do so well. Thus, it's optimized for relatively light street/strip cars--today's porky 4,000-pound Mustangs need not apply--with a bit of gear in the rearend.

On the other hand, the XT is not an all out racing intake for screaming 9,000-rpm small-blocks. That's what Victor Jr.'s are for. As Brent put it, "The XT is a tunnel ram with the throttle body in a convenient place for plumbing. If you wanted max power you'd have a pair of four-barrel throttle bodies on top of the plenum. But the [XT] runners are short enough that they won't be harmful at any conceivable rpm. The XT manifolds are capable of going to 7,000 or 7,500 rpm, and as they are, the XT are optimized for 6,500 or maybe 7,000 rpm."

Befitting a street/strip car, "the XT is more broad in its power. The Victor Jr. has one less turn for the air than this XT design, so ultimately the spider-type [Victor Jr.] would outflow the XT on top end. But the XT offers equal-length, more tuned runners, so the average will be better, with more area under the curve."

As Brent ran us through the XT's development, we realized there are two XT intake stories. The first is the standard how and why of its design, the second is the design and development process itself. This is one of the first intakes Edelbrock has developed entirely in a computer, including the manufacturing tooling, plus prototyped using plastic rapid prototyping parts. The result is the first XT intake cast in Edelbrock's foundry was nearly the first production part.

Brent started the XT's design by laying out the core, or inside of the manifold on his Pro Engineer software. At this point, "I paid attention to runner area and runner lengths," plus the important blend of the plenum into the runners. This aperture was made 2.8 square inches, with the runners slightly tapering to 2.05 square inches at the cylinder head end. "This is the only taper or change in cross-sectional area in the intake," said Brent.

"There is another [computer] file of the casting, which has all the bosses, the draft, so you can see all the parts, see the actual manifold," Brent explained as he moused over the XT's design on his computer monitor. "This is the second piece of the puzzle." Additionally, besides the core and casting files, there is a machining file that shows the intake after its trip through the CNC machine. "The core, the casting, the machined piece; these three files are joined into the "assembly." As you can see, it's starting to get pretty complex." And for a simple intake layout we had to agree as he rolled the stick figure XT intake around.

This assembly of Pro Engineer computer files was then imported to an existing file of a small-block Ford V-8. "This allows checking the distributor clearance and other crashes that may occur," Brent explained. "The throttle body was placed so you could get the cap and rotor out without touching the manifold. I checked the fuel rails, the cylinder head, the rocker cover rail... you can you get a wrench on the temp sensor with the valve cover on, you can line up the linkage for the throttle brackets..."

As Brent pointed out, when working with later-model cars the CAD files of the entire engine compartment are available from Ford, so the Edelbrock intake can be electronically verified in the car and under the hood before the first intake is ever made. Obviously this saves weeks of pattern making, casting, and redesign.

Finally, the multi-part computer file was sent to a Dimension 3D printer where the intake first took material form overnight as a plastic part. One computer step not taken with the XT intake was a CFD or Computational Fluid Dynamics analysis. This is where the intake's flow path has electronic air sucked through it by an electronic engine to arrive at a "video" of the air molecules racing through the intake. Edelbrock certainly has this capability--they showed us a fascinating CFD file from another intake--but the cumbersomely slow process (on less than supercomputer architectures anyway) was deemed unnecessary for the simple XT intake. This is, after all, not Edelbrock's first rodeo.

Insuring no lack of air to the crate engine is Edelbrock's newer 90mm throttle body. This is an evolutionary piece designed to iron out the installation wrinkles in previous throttle bodies while assuring adequate airflow. Highlights of the new 90 are it uses a Ford TPS and IAC valve for easy, familiar parts availability. And, Brent pointed out, "It has the left-side linkage, which is proper. You no longer have to use the right side linkage, which required snaking the throttle cable to the other side of the engine."

As an aside, Edelbrock has air intake elbows for fitting EFI to single-plane carbureted intakes and the new 90mm throttle body works on these elbows as well. "So, if he has a Victor EFI manifold and electronics, now he can run the Ford 90mm with the proper IAC and TPS," Brent said.

So, after all the computer design and prototyping, sometimes it still comes down to a little dirty work in the grinding booth during final development. By the time you read this the injector bosses were long ago slimmed down for production manifolds--something easily done when you own your own foundry--and the XT system should be on sale. When you step back and take it all in, the XT is a remarkable achievement for an aftermarket company. To design and build a complete, dedicated carburetor-replacement system is no mean feat, after all. And with this new intakes, the recently released E-Force supercharger, and continuing crate engines, the Big E is definitely in the hunt for Ford performance.

XT Pricing
Tariff on the Ford version of the XT intake system was not set at our deadline. However, a Chevy version of the system is already on sale thus giving a good idea on Ford pricing because both systems include the same parts. For a complete Pro-Flo XT EFI Intake and System expect about a $3,300 price tag. This is a complete carburetor-to-EFI conversion kit and includes the XT intake manifold, fuel rails, injectors, distributor, XT ECU, Calibration Module, wiring harness, oxygen sensor, fuel pump, and small parts.

The XT intake manifold by itself should be $420, roughly. The XT cylinder head, dressed with valves and springs is just over $1,000. Edelbrock's existing 347 Ford crate engines, which are complete, with a single carburetor, start at about $9,600 so adding the XT upgrade means they'll certainly be over $10,000.