Small-Block Top-End Swap - Big Power For Little Cash

Swapping Top-End Parts to Make 523 Horses

Bob Mehlhoff Dec 1, 2006 0 Comment(s)

Step By Step

It's all about flow, baby
For our testing we used the new AFR 195 Street Eliminator cylinder heads on our 388 small-block. The final compression ratio using these heads is about 10.6:1 so 91-octane fuel is required for operation.

The ports in the Eliminator heads are shaped to achieve good velocity through a relatively small cross-sectional port. This design promotes strong low- and midlift flow numbers, while still achieving a high peak flow number. Although the heads are initially designed by hand and lots of experience, the final product is completely reproduced on a CNC machine. This production method ensures that all of the ports flow the exact amount of air with the same velocity.

Let It Flow
For a quick reference we've listed the flow data from the original street heads against the new Eliminator versions. It's important to point out that even the previous cylinder heads produced solid flow numbers when measured against others in the aftermarket, and the new versions take it over the top. Note that the new head flows 278 cfm at 0.500 inch lift, which is important because most serious street cams have maximum lift just past the 0.500-inch point.

For our baseline run we ran the Edelbrock Performer RPM Air Gap intake manifold. This manifold is a dual-plane intake and provided the highest torque numbers. For the remainder of the testing we ran the Edelbrock Victor Jr., an open-plenum intake, for our highest peak-horsepower figures. Airflow below the plenum on either manifold keeps the intake charge cooler and denser for added power.

To free even more power, the Eliminator head uses lightweight 8mm stem valves, retainers, and locks. With both intake and exhaust considered, each cylinder has shed 103 grams. The lighter the valvetrain, the more accurate the valve motion control at high rpm. This simple change allows an engine to continue operation higher in the rpm band, while delivering added horsepower.

The mission: Take a purse of about $2,750, a willing 388ci small-block, and make over 500 hp by adding some of the industry's best top-end bolt-on performance parts. To fulfill this tall but doable order requires an exceptional set of cylinder heads, a well-thought-out camshaft design, and an intake manifold to supply the engine with sufficient airflow. As you already know, more air means more power.

Cylinder-head technology has advanced light-years from what was available only a generation ago. This is largely thanks to the combination of several key factors including lighter-weight components and flatter, more efficient valve angles formerly associated with high-end race stuff, producing the most efficient power measured under the curve.

Suffice to say, Air Flow Research (AFR) has been very busy staying ahead of the cylinder-head development curve, as evidenced by the recently released Eliminator series, an all-new cylinder head for street or competition that increases flow numbers significantly over any previous design. This new benchmark has been accomplished by completely redesigning the combustion chamber, ports, throat area, and valve job on a 23-degree head, creating a greatly improved cylinder head from top to bottom-with the flow numbers to prove it. At 0.500 inch lift this head flows an impressive 278 cfm on the intake side, which is a 17 cfm increase compared with the original design, which flowed less (though still respectable at 260 cfm). For even more power, you can expect a competition version by the time you read this.

Of course, when we first learned about the Eliminator heads, we had to see how well they would perform. Lucky for us, we're in pretty tight with AFR's cylinder-head guru, Tony Mamo, and we managed to bug him into letting us test a pair, but not just any pair; we actually got the very first pair. After describing our test mule, and at Mamo's recommendation, we opted to try out the larger 195 version over the 180s and set a date to meet him at the Westech Dyno facility, where we spent the entire day flogging his latest creation on our trusty small-block 388. A quick one-time pull wouldn't do anyone any justice, so we tested them in several configurations that included two Comp Cams camshafts (XE274H and XE284H), an Edelbrock Performer RPM Air Gap and an Edelbrock Victor Jr. intake, and two sets of Pro Magnum roller rockers (1.52 and 1.6 ratios). By the end of the day, we had made an unimaginable number of dyno runs and had our story. From mild to slightly wilder, we show two distinctly different combinations that both made incredible power; however, if you opt for the slightly more aggressive configuration shown here you can actually expect to save a cool $20. Check out the details, and be sure to e-mail us at chevyhi@sourceinterlink.com and let us know which combination is your favorite.

QUICK NOTES

What we did
Dyno-flog AFR's latest 195 Eliminator street heads, show the difference in gains between the Edelbrock RPM & Victor Jr. manifold, and push the limits with two camshaft grinds from Comp Cams.

What we did
Dyno-flog AFR's latest 195 Eliminator street heads, show the difference in gains between the Edelbrock RPM & Victor Jr. manifold, and push the limits with two camshaft grinds from Comp Cams.

Price (APPROX)
$2,750 in top-end parts (not including carb)

The new head is the result of intense research and development into the new Eliminator series. Mamo tells us that when he designs a new head like the 195 Eliminator, he begins at the combustion chamber, works his way up to the valve job, then tackles the ports. The combustion chamber's shape is critical to flow because it helps shape the umbrella of air coming off the intake valve, and helps direct the air into the exhaust port. The process of designing a performance cylinder head is largely rooted in old-fashioned trial-and-error, shaping almost everything by hand and using some epoxy. Only then is the finished product's final design digitally programmed so that it can be recreated to other cylinder heads on a CNC machine.

Eliminator 195 Street Head

THE CAMS

Tests 1-2
Comp Cams Xtreme Energy (XE274H ) flat-tappet hydraulic cam, PN 12-249-4
Intake/exhaust lift at cam lobe: 0.327 inch
Intake/exhaust lift w/1.52 rockers: 0.496 inch
Lobe separation angle: 110 degrees
Duration measured at 0.050: 230/236

Tests 3-6
Comp Cams Xtreme Energy (XE284H ) flat-tappet hydraulic cam, PN 12-250-3
Intake lift at cam lobe: 0.338 inch
Intake lift w/1.60 rockers: 0.540 inch
Exhaust lift at cam lobe: 0.340 inch
Exhaust lift w/1.60 rockers: 0.544 inch
Lobe separation angle: 110 degrees
Duration measured at 0.050: 240/246

Meet The Mule

HEADS
AFR 195 Eliminator street head (PN 1040)
195cc port, 65cc chamber (milled to 64 for the test)
2.055-inch intake/1.600-inch exhaust, 8mm valve-stem diameter with bead lock-style groove

SHORT-BLOCK
388ci small-block
Bore: 4.060 inches
Stroke: 3.750 inches
Block deck height: milled to 9.005 inches
Piston deck height: 0.000-0.003 inch
Piston dish: 6cc
Compression: 10.6:1 (approx.)
Rod length: 5.700 inches
Piston compression height: 1.430 inches
Piston-to-wall clearance: 0.005 inch
Main bearing clearance: 0.023-0.027 inch
Rod bearing clearance: 0.025-0.027 inch
Rod side clearance: 0.016-0.020 inch
Rod side-to-piston clearance: 0.125 inch
Ring end gap: 0.022/0.020/0.032 inch
Piston-to-head clearance: 0.041 inch
KB Forged pistons, PN UEM-KB-704

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