In the first two parts of this engine series — the introduction and the bottom-end — we introduced the Dart billet block along with the jewelry encompassing the Callies billet crank rotator with its JE Pistons and aluminum GRP connecting rods. Those parts have established the rock-solid foundation – Project Evil’s bones if you will. The goal is monster four-digit power from a relatively conservative 438 cubic inches, so the cylinder heads and valvetrain have to play well together to make this happen.
However, before we scamper down the rabbit hole of technical geekness, we should first set a couple of parameters. From our previous story, team owner James Lawrence and engine builder Jon Bennett of KBX Performance opted for a Dart billet block. They chose conventional bore spacing mainly because the rules dictated cast aluminum heads. Billet was selected for its strength (a forging is always stronger than a casting). Plus, the standard Ford 9.500-inch deck height was retained due to concerns that a rules change might obsolete a tall deck block.
But this standard deck also limited the size of the cam journal. While a 60mm cam core offers strength advantages, the deck height decision forced the selection of a slightly smaller 55mm cam core to increase cam lobe to connecting rod clearance, especially with aluminum rods, which grow at twice the rate of steel when they get hot. These are the limitations and compromises necessary in order to build a competition engine.They are generally things you learn only after building dozens of successful versions.
Head of the Class
With those parameters set, Lawrence and Bennett selected a set of Edelbrock Glidden SC-1 heads. This is a canted-valve configuration which can trace its lineage back to the Cleveland days, but that’s about where production similarities end. The valve angles are slightly taller than a stock Cleveland by just a couple of degrees. The Edelbrock/Glidden casting is supplied to engine builders with rough-cast ports, offering plenty of material to allow the engine builder to establish exactly the port cross-section and valve sizes he needs for the particular application.
KBX’s CNC work establishes the shape of the port and we’ve attached a flow sheet Bennett supplied, which shows just how much air the intake and exhaust ports can muster. The nearly 470 cfm at 1.00-inch of valve lift number is stellar, but consider this is just with the atmosphere moving air through the flow bench.
Add a considerable push from double-digit boost numbers and the mass flow has to be equivalent to an F5 tornado. Keep in mind port volume will be slightly larger if for no other reason than to accommodate the buckets of methanol coursing down these ports in volumes twice that of gasoline.
Bennett filled us in on a few of the details for the heads. “The heads were packaged with 2.200-inch intake and 1.600-inch exhaust valve sizes. We would optimally like to see a 2.250-inch and 1.600-inch package, but the Edelbrock SC1 guide spacing does not allow that,” Bennett explains. “We have run some 2.225-inch intake valve stuff in the past, but we’re concerned about valve-to-valve clearance under high RPM or with a power adder. So we currently use the 2.200-inch and 1.600-inch combination.”
Size determined, Bennett opted for Ferrea valves for this combination, due to their consistent quality in extreme performance applications. The intake valves are a high-temp stainless steel pieces, measuring 2.200 inches, with Ferrea’s Super-Flo configuration, which is Ferrea’s valvestem undercut process. By reducing the diameter of the valvestem — right above the head of the valve in a very specific amount and location — flow is increased without reducing the strength of the valve. The planned RPM range for this engine didn’t really warrant use of titanium valves — even at this large diameter.
Since exhaust valves tend to live a harsh life in supercharged engines, Bennett stepped up to Ferrea’s Inconel IN-751 alloy for the 1.600-inch exhaust valves. Inconel is a “superalloy” that can withstand extreme exhaust temperatures better than stainless steel, and are rated to 1800 degrees Fahrenheit. Ferrea also incorporates a radius on the face on the exhaust valves, which improves flow compared to sharp angles used on intake valves.
Sealing the heads to the block is no small feat, and as we mentioned in the short-block article, the block has been machined for KBX’s fire ring setup. To compliment that, a set of Cometic head gaskets are utilized. But not the usual MLS offerings you picture when you think “Cometic”, but rather its dead-soft copper offerings. Manufactured with six bolt holes per cylinder and no water passages, the Cometic copper gaskets are perfect for this application. With a compressed thickness of .051-inch and only .030-inch over bore size, the chamber volume is kept precise.
The Brain of the Combination
Cam selection was next on the list. Bennett chose to go with a 55mm, 8620 steel camshaft core from COMP Cams. While the mechanical roller camshaft’s specific lobe family specifications gets inside what might be called intellectual property, Bennett did share that the cam is designed to operate the valves with 280- degrees (intake) and 295 degrees of duration (exhaust) at 0.050-inch, with a peak valve lift of a whopping 0.950-inch and a lobe separation angle (LSA) of 116 degrees.
The LSA is a larger number (wider in degrees) mainly to improve power when using a supercharger. This wider LSA reduces valve overlap, which can sacrifice boost (and therefore power) by allowing the pressure to push air and fuel directly past the exhaust valve rather than remaining in the cylinder. With the Vortech XB105 moving tons of air, it wouldn’t be wise to let it all out before it was combusted.
The greatest cam specs are nothing if they can’t be accurately and reliably timed to the crankshaft’s rotation. To handle that task, KBX turned to Danny Bee. Using an aircraft-grade billet aluminum housing, an 8620 steel crankshaft gear, and anodized 6061 aluminum cam gear, with a 30mm Goodyear cogged drive belt, the belt drive unit is designed to live in the harshest of conditions.
Belt drives are not only easier to manipulate than chains, but also allow for extremely fine adjustments on the fly. The Danny Bee drive includes a simple adjuster on the face of the cam gear allowing up to 20-degrees of camshaft centerline adjustment just by loosening the adjuster lock bolts. There’s also a scale right on the face of the gear which makes minor adjustments easy.
Of course power production relies heavily on the concept of the valves opening and closing at the appropriate times, especially at 8,000 rpm. This means not only a durable valvespring, but also the correct combination of lightweight retainers, locks, rocker arms and pushrods. All of the components have to work in concert to ensure the valvetrain control is regimented properly.
With the competitive nature of this engine, the use of titanium hardware wherever possible is key. Thanks to Manley Performance, that’s not a problem, even with the taller-than-normal valves. Using a .062-inch spring locator, a set of 10-degree titanium .100-inch-taller retainers, with complementary titanium 10-degree Bead-Loc valve locks. Topping off the valves are a set of Manley’s TensileMax wear caps made from Manley’s Ultra High Strength Steel, which is heat treated and through-hardened to Rockwell HRc 55 for maximum wear resistance.
Flow numbers for Project Evil’s Bennett Racing-ported Edelbrock SC1 heads. These numbers were established using 28-inches of test depression.
Fighting the Good Fight
If there is an ultra-critical part on any pushrod race engine, it has to be the valvesprings. These will be the pieces receiving the most attention and also the most abuse. Manley supplied the NexTek dual valvesprings that measure 1.500 inches in outer diameter and have an installed height of 2.150 inches. This greater installed height is necessary when building an engine capable of nearly an inch of valve lift.
The springs can generate 405 pounds of seat-load and every bit of 1,155 pounds of open pressure. This demands a reliable rocker shaft system both to be able to control these massive loads, and also to work against substantial cylinder pressure. What is often overlooked on supercharged and turbocharged engines are the rather serious cylinder pressure loads the exhaust valve has to work against at high-RPM.
If the exhaust valve is opened too early, it can be faced with excessively high residual cylinder pressure. If, as an example, there is 500 psi remaining in the cylinder when the rocker pushes on the valve to open it, the rocker arm must work against just over 1,000 pounds of force (500 psi x 2.01 sq.in of exhaust valve face surface area = 1,005 pounds). At high-RPM, the exhaust valve must open early enough to give the cylinder time to blow down.
The rocker shaft system Bennett called upon for this part of the operation was supplied by T&D using steel rockers to withstand the anticipated high loads. “We had T&D Machine Products make us a custom stand, which was designed to match our valve length,” says Bennett. “By designing the stand height specific to the valve length, it keeps us from having to use shims under the rocker stand. For the rocker arm ratio, we decided on 1.75:1.”
While a higher rocker ratio creates more lift, it also generates greater load. This stress is imparted all the way back through the pushrod. To hammer this home, consider this simple, static load example. If we multiply the open valvespring load of 1,155 pounds times the 1.75:1 rocker ratio, this places over 2,000 pounds of force directly on the pushrod. This simple calculation does not take into account the much higher dynamic loads that occur when attempting to slam valves open and closed at 8,000 rpm.
Powerlifting Isn’t Just For The Gym
To handle those insane loads, the pushrod part of the engine equation fell in the professional hands of Trend Performance. For this application, Trend supplied a set of monster 1/2-inch tapered pushrods with stout 0.200-inch wall thickness for the intake side, and slightly thinner 7/16-inch tapered versions with 0.165-inch walls for the exhaust side.
This also means only the best lifters should be considered, which is why Bennett selected a set of Jesel keyway-guided 0.937-inch diameter lifters for the task. This also required a few custom touches. “We used Jesel 0.937-inch keyway lifters that are a custom item for us. Keyway lifters are almost normal fare for race engines now because they eliminate the tie bar, which adds weight. The keyway rides in a slot in the lifter bushing that locates the lifter relative to the cam lobe,” explains Bennett. “A conventional keyway lifter body design is too short for our Ford engines because the key will bottom out on the bushing. Jesel makes our lifter taller to give us ample clearance for keyway travel.”
The “0.937-inch” spec references lifter diameter. A normal small- or big-block Chevy lifter is only 0.842-inch in diameter while a production Ford lifter is 0.875-inch and a Chrysler is 0.904-inch. This larger 0.937-inch body width allows a larger 0.875-inch wheel which reduces lifter body side-loading and increases the contact area between the wheel and the camshaft lobe.
Of course, the custom building efforts don’t stop there but we will temporarily halt the discourse here until the next episode of Project Evil. We’ll return after a short respite to detail the forced-induction side, which includes the Vortech XB105 blower and Chris Alston CDS supercharger gear-drive system plus we’ll take a look at how KBX is generating the huge methanol flow numbers required to feed this monster. Until then, think Evil thoughts!
KBX Performance 438 SBF Top End Spec Sheet
|Heads||Edelbrock Glidden Victor SC1, Pro-Port cast-aluminum cylinder head|
|Porting||KBX Performance CNC, 470 cfm intake, 300 cfm exhaust|
|Head Studs||ARP stainless steel, custom length, six per cylinder|
|Head Gaskets||Cometic copper gasket, 4.130-inch bore, .051-inch thick, no water, six-bolt heads|
|Valves||Ferrea 2.200-inch stainless steel Super-Flo intake valves, 1.600-inch IN-751 Inconel exhaust valves|
|Valvesprings||Manley Performance NexTek dual springs; 405 lbs seat pressure, 1,155 lbs open pressure.|
|Retainers||Manley Performance Titanium 10-degree, +0.100-inch height|
|Locks||Manley Performance Titanium 10-degree +.050-inch, Bead-Loc|
|Locators||Manley Performance heat-treated 0.62-inch steel|
|Wear Caps||Manley Performance TensileMax through-hardened Ultra High Strength Steel|
|Camshaft||COMP Cams 55mm 8620-steel custom mechanical roller, .950-inch lift, 280/295 @ .050-inch, 116 LSA|
|Timing Set||Danny Bee Racing Belt Drive|
|Rocker Arms||T&D Machine 1.75:1 billet-steel, needle-tip, shaft rockers, +.100-inch|
|Pushrods||Trend Performance 1/2-inch tapered, .200-inch wall, intake; 7/16-inch tapered, .165-inch wall, exhaust|
|Lifters||Jesel .937-inch, keyway-guided mechanical roller, custom-height|
|Valve Covers||Moroso custom billet aluminum|