It may have been born on the wrong side of the tracks, but our "500 HP For Cheap," 383ci small-block Chevy (Sept. '06) has shed its humble origins and put on some class-namely, the 600hp class. Ace engine builder Joe Sherman has stepped up, metamorphosing our humble sow's ear into a silk purse, bolting on some serious parts to boost power as well as long-term reliability.
The genesis for the upgrade was an opportunity to test Air Flow Research's new Eliminator aluminum heads. Prototype castings were made available to us, and our budget 383 was handy, so we figured why not try to raise a 528.5hp mill over the 600hp barrier? Obviously, more cam was needed, and with more cam, much stouter valvesprings were required. The bigger springs wouldn't fit the heads without longer valves, and the longer valves generated valvetrain-geometry issues. Solving those issues required premium valvetrain components. But that's hot-roddin'. And we're getting ahead of ourselves. Let's begin at the beginning.
For the test, the 383ci short-block, less cam, remained in its original, budget Street Fighter configuration as built by Coast High Performance. The preassembled crate package consisted of a two-bolt-main 350 block bored 0.030-over and stuffed with a 3.75-inch-stroke, cast-steel crank that swings profiled CNC beam-forged 5140 steel, 5.7-inch center-to-center rods fitted with full-floating, flat-top, CNC-machined forged pistons.
Air Flow Research heads have a stellar industry reputation. But as good as its current heads are, technology does not stand still. AFR thought it was time for a major design enhancement, and the result was its new Eliminator head series based on a common CNC-machined casting. Equivalently sized Eliminator configurations are coming online to replace all AFR's current small-block Chevy heads, including the 180, 195, and 210cc street heads, plus the 220, 227, and raised-port 215 race heads. Like AFR's previous head generation, the new configurations will be fully CNC-ported with a choice of two levels: street or competition. Competition porting produces a more finely detailed port that more accurately reproduces the as-designed surfaces-but it takes longer, so it's more costly.
Whether they are street- or competition-ported, the various Eliminator heads will be otherwise identical in terms of valve sizes and port shape and volume with one exception: The 195cc street heads have 2.055 intake/ 1.60 exhaust valves; with the intake-port entrances sized for Fel-Pro PN 1205 intake gaskets, they mate well with Edelbrock's Performer RPM, RPM Air Gap, and Victor Jr. intake manifolds. The 195cc competition heads' intake entrances are sized for the larger Fel-Pro PN 1206 intake gaskets and use a bigger 2.08 intake valve (1.60 valves are still used on the exhaust side).
In Sherman's experience, a 383 small-block needs at least a 210cc intake-runner volume to make serious power. In fact, our budget 383 had been using aftermarket iron heads with a 220cc intake runner, 2.02/1.60 valves, and angled spark plugs. Unfortunately, the only available AFR Eliminator heads ready in time for our short-lead-time test were prototype 195cc street-ported heads, which would be giving away 25 cfm of port volume (although their 2.055 intake valve is larger). However, in tests on Sherman's SuperFlow bench, these prototype 195 street heads hit 280 cfm at 0.500-inch lift with some of the most impressive low- and midlift numbers Sherman had ever seen.
AFR said the competition 195s should reach 300 cfm at 0.600 lift. The larger 210cc configurations are said to flow a whopping 310 cfm at 0.600 lift with even more available at higher lifts. Official numbers aren't yet available for the 220cc heads, but rumor has it that they should flow over 320 cfm. All this, and the heads still retain the traditional 23-degree Chevy small-block valve angles and spacing, making them true, bolt-on performance enhancers.
Comp Roller Cam
A tried-and-true way of making more power is to spin the engine higher. Not only does this mandate a stout cam and valvetrain, but it also requires that the short-block be reliable enough to hold up to higher rpm's added abuse-bottom-end loading increases by the square of the increase in rpm. But as Sherman put it, "The short-block we are using is not a racing short-block. It has no four-bolt [main] caps." Cam selection, therefore, represented a fusion of the need to keep the engine alive and the need to achieve our power goals. In Sherman's estimation, the new cam needed to peak at about 7,000 rpm with a redline of 7,300-7,400 rpm. Based on those constraints, and also taking into consideration the recent troubles the industry has experienced with flat-tappet cam profiles, Sherman spec'd one of Comp Cams' standard catalog listings: a tight lobe-separation, oval-track mechanical roller grind No. 287TKR-6. With the hairy cam, piston-to-valve clearance came in at a tight 0.050-inch intake/ 0.060-inch exhaust, but Sherman wasn't worried: "With a [solid] roller cam, the valves can't float unless you really have a problem. I feel comfortable at this level."
Keeping the cam under control requires a stout yet lightweight valvetrain. The lighter you can make the components without inducing part failure, the easier the engine will rev up to its required rpm goal-so special roller lifters with a cut-down body plus titanium retainers were installed along with Comp's lightweight Hi-Tech dual valvesprings. This valvespring/retainer assembly has a larger diameter and is also taller than the hydraulic roller cam-compatible springs AFR's street heads are usually delivered with . . . and that's why the valvetrain situation began to get a little sticky.
Accommodating the larger, taller valvesprings ultimately required both machining the existing valve pockets 0.100 inch deeper and swapping in 0.100-inch longer-than-stock valves. Why not just use offset valve locks? We weren't going to get off that easily: The new AFR heads use valves with the LS engine-style, 8mm-od valve stems machined for groove-lock valve keys in place of the traditional small-block Chevy's 111/432-inch stems machined for old-school, square-groove keepers. The smaller valve stems save weight, while the bead-lock adds durability, but the downside is that offset keys and similar devices normally used to help correct geometry and interference issues are not available in this configuration. Fortunately, AFR had the necessary 0.100-inch-long valves in stock, but the longer valves ended up adversely affecting valvetrain geometry.
Different-length pushrods, the usual geometry-correction method, proved untenable because the right-length pushrods resulted in the rocker arms contacting the valvespring retainers. Even assuming no retainer-clearance issues, Sherman maintains that, in his experience, optimum (as opposed to marginal) geometry cannot be obtained on a conventional small-block Chevy stud-mount valvetrain with 0.100-inch-long valves because the rocker's arc of travel across the valve-stem tip still ends up way off the original factory design intent.
Although you could relocate the rocker-arm stud (which requires considerable modification, including welding, drilling, and tapping), at this point, the sensible solution is to bite the bullet and move up to a shaft-mount valvetrain, such as Jesel's Sportsman design. Besides being inherently more stable at high rpm, the Jesel design improves the geometry by relocating the rocker's pivot fulcrum centerline with no need for custom machining. Of course, they're not cheap.
Weird pushrod lengths are not usually needed with the Jesel setup. You can shim the rocker stand to raise its height, or if needed, you can mill the bar or pads the rocker arm screws down onto to lower the assembly height. In fact, using 1.6:1 intake and 1.5:1 exhaust rocker ratios on this engine, the Jesel setup did such a good job that Sherman was able to achieve the correct geometry using 7.800-inch-long, standard-length small-block Chevy pushrods plus the 0.100-inch-thick shims included in the Jesel kit. By contrast, Sherman said the stud-mounted valvetrain would need 7.950-inch pushrods-and "it still wouldn't be ideal."
Comp Hi-Tech dual springs (PN 26089) get the job done with smaller-diameter spring wire. That saves weight and eliminates the need for a damper and its extra mass. AFR supplied the seals for its 8mm all-metal valve stems. Weighing just 10 grams, the newest Comp titanium retainer (PN 720) is cut down in noncritical areas to shave 4 grams off the 14-gram weight of the previous-design titanium retainer. "The retainer is the biggest thing that adds mass to the spring," Sherman says. "Cut weight here, and you can add 200-300 rpm to the top end of the rev band."
The engine was installed on Sherman's SuperFlow 901 dyno with the same induction and exhaust components used during the motor's previous budget incarnation: Patriot 131/44-inch primary-tube headers running through Hooker 3-inch AeroChamber mufflers, an Edelbrock Super Victor intake manifold, a Summit 1-inch phenolic open carb spacer, and a Speed Demon 850-cfm vacuum carburetor. The original GM HEI was upgraded to an MSD distributor and ignition-control box. A Milodon drag-race oil pan, a high-volume pump, and a corresponding pump screen enhanced the oil system. Every little thing counts for making those big power numbers, so Sherman even spec'd out the spark plugs, using NGK R5672-8 plugs-a medium-cold, projected-tip, wide-gap racing design. Provided the ignition is up to the job, wide spark-plug caps (0.060 inch in this case) can be worth 5 or so horsepower. And the projected tip lets the engine make that power with 3 degrees less total advance. With total timing set to 35 degrees on 91-octane Chevron unleaded pump gas, Sherman was ready to pull the throttle lever.
Sherman found the 850-cfm, vacuum-secondary carb was too lean, which required stepping up about three jet sizes each on the primary and secondary sides to No. 86 and No. 94 jets respectively. Once the fuel curve was dialed in, the motor achieved our goal, making over 600 hp from 6,500 through 7,000 rpm and peaking at 605.8 hp at 6,700. Over 500 lb-ft of torque was developed between 4,800 and 5,700 rpm, with the peak of 521.2 lb-ft occurring at 5,000 rpm. Still, the curve was slightly ragged, and Sherman felt that installing his favorite Mighty Demon 850-cfm double-pumper should both smooth out the curve and make more peak power.
Mechanical-Secondary Carb
The Mighty Demon is Sherman's go-to dyno-mule carb. Without a choke tower, it has smoother airflow, plus its out-of-the-box 86/94 jetting was just what the engine liked. Bolting it on in place of the vacuum model smoothed and broadened the curves. The peak torque point was raised 200 rpm to 5,200, where the engine pounded out 528.5 lb-ft, a gain of 7.3 lb-ft over the vacuum-carb configuration. Even better, the engine now made a 615.4hp peak at 6,800, nearly a 10hp gain; it made over 600 hp from 6,400-7,200 rpm.
Head-Flow Data
New AFR Eliminator 195cc intake port street heads equipped with 2.055/1.60 valves were flowed at 28 inches of water by Sherman on his SuperFlow bench.
At 7,000 rpm, valvetrain mass becomes critical; it needs to be as light as possible without sacrificing critical stiffness. With its cut-down upper body, Comp's lightweight mechanical roller lifter (PN 888-16, right) shaves 34 grams off the full-bodied lifter (left)-despite a 0.300-inch-taller body that permits the guide bar to clear a Bow Tie block's taller lifter bores.
LIFT (INCHES) INTAKE (CFM) EXHAUST (CFM) 0.{{{100}}} 70.4 56.7 0.200 149.5 114.1 0.{{{300}}} 201.2 {{{164}}}.9 0.400 253.2 199.6 0.500 280.2 217.7 0.600 277.0 222.1 0.700 276.1 225.9
The Price Of Performance
Assuming retention of the CHP preassembled short-block, the engine as tested with the remanufactured vacuum-secondary Speed Demon 850-cfm carb costs about $9,200. Substituting the Mighty Demon 850 double-pumper adds about $80 to the price, bringing the total to just under $9,275. You could lop off $445 from the price by buying the heads fully assembled from Air Flow, including the necessary mechanical roller-cam upgrades. Finally, as noted in the original article, assembling the short-block and rotating assembly yourself would cut another $371 off the price, bringing the bottom-line cost in at under $8,460.
Any way you slice it, 615 hp from a set of street heads is indicative of just how far engine technology has advanced. Also worthy of note is that the power ended up peaking at only 6,700-6,800 rpm, not the 7,000 rpm Sherman originally intended. This indicates the need for an even larger port-if the small 195cc intake port and a catalog cam can make 1.6 hp/ci on a pump-gas 383, one can only imagine what AFR's new 210 or 220cc Eliminator heads will be capable of once they become available.
DYNO RESULTS {{{850}}} VACUUM 850 DOUBLE-