Contemporary Technologies Drive an All-Alloy, Naturally Aspirated Small-Block to 700+ hp and 614 lb-ft

By Barry Kluczyk – Photography by the Author

News flash: Enthusiasts are still building big power from old-school small-block engines.

With 436 ci, natural aspiration, and EFI, the project engine we’re going to discuss in this story spun to 7,300 rpm and lit up the dyno with 708 hp and 614 lb-ft of torque. That was with a comparatively small camshaft and a pump gas–friendly compression ratio.

Those peak numbers are impressive, but perhaps more so was the fact that its glorious, neck-tugging torque came in immediately in the powerband: 451 lb-ft at only 3,500 rpm. That’s only 19 lb-ft short of the factory LS7 engine’s peak torque of 470 lb-ft, which occurs at 4,800 rpm.

The foundation for the build is an aluminum Dart small-block casting that previously served duty in a circle track race car. It has an 8.995-inch deck height and, per Dart’s design, a raised camshaft position that provides more room for a stroker crankshaft and a larger-base -circle camshaft. The block weighs around 95 lbs.pounds, which is about 100 lbs.pounds less than a production-spec iron block.

Comparing this small-block, which was designed and built by John Lohone, of Michigan-based Valley Performance, with the vaunted LS7—the naturally aspirated king of LS engines—may seem an apples-to-oranges matchup, but the parallels are surprisingly similar. The displacements are within 9 ci and both have similar compression ratios and rpm capabilities. And as mentioned above, this small-block is naturally aspirated and employs electronic fuel injection just like the LS7.

One more thing: Both have an aluminum block and aluminum heads, as the small-block is based on a Dart casting. Builder Lohone was strategic in the design of the engine and because it was intended for a replica of the small-block–powered Cheetah race cars developed by Bill Thomas he was insistent on the lineage of the powerplant.

Ductile iron, 4.165-inch-diameter sleeves in the aluminum block were honed at Valley Performance to 4.166 inches, allowing a piston-to-wall clearance of 0.005- inch. With the crankshaft’s 4.000-inch stroke, the displacement is a healthy 436 ci.

“It would have been easy to drop in an LS crate engine and hit the street and track, but I wanted the engine for this car to honor what the original Cheetahs ran,” Lohone says. “Using an aluminum block and heads offers the enhanced weight balance that an LS engine would have delivered, but with the classic small-block sound and feel.”

Let’s talk about that feel for a moment because for all their high-revving capability, LS engines—and LTs for that matter—just don’t compare to a small-block when it comes to low-down, guttural torque production. It’s an immediate feeling of power, which the dyno results for this engine corroborated.

Oil control mod Number 1: A lead-in groove was carved into the coated main bearing for the main oil feed to the main bearing oil feed hole; along with a lead-in groove in the bearing to the oil feed hole in the main journal to the rods. This was done to the central three main bearings, because they feed two rods apiece. The front and rear mains feed only one rod each, so those bearings weren’t touched.

“We were looking for 700 naturally aspirated horsepower, which we achieved,” Lohone says. “But the real surprise was the broad torque band. It starts early and hangs on all the way to the end.”

Indeed, it does. The engine achieves 500 lb-ft by 3,800 rpm, peaks at 614 lb-ft by 5,300 rpm, and still makes a healthy 537 lb-ft at 6,900 rpm. It’s a very strong showing for an engine decidedly not built as a purposeful track weapon.

“The goal is to drive it on the street and have fun at track days,” Lohone says. “It’s not a racing engine. More camshaft and a higher compression ratio would have significantly upped the dyno numbers, but this is very strong performance for a pump-gas engine, with a very wide and usable powerband.”

Oil control mod Number 2: The pipes threaded into the valley oil-drain holes help reduce windage by preventing oil from dripping onto the camshaft. They also serve as vents, allowing an upward outlet for crankcase pressure that doesn’t have to fight oil trying to drain back to the oil pan.

Stacked for Performance

The basic ingredients for this big-inch small-block include a Dart aluminum block with large, 4.165-inch bores, ported Edelbrock 18-degree aluminum heads (with 66cc chambers), a forged rotating assembly (with a 4.00-inch stroke), a roller cam (with big-block journal sizes) with 0.757/0.758-inch lift and 254/264-degrees duration at 0.050-inch, a Jesel beltdrive system, and a hall-effect crank trigger. Aspiration comes from a Kinsler EFI system that’s directed with a Holley control system.

“The look of the injector stacks is period-appropriate for the replica Cheetah,” Lohone says. “And the Kinsler system flows a lot of air, so it performs as well as it looks.”

Machinework and assembly were performed at Valley Performance, where Lohone works, while dyno testing took place at BES Racing Engines, in Southern Indiana, where the racing-engine specialist has a strong reputation for tuning Kinsler injection systems.

The crankshaft is a K1 4340-forged-steel piece that delivers a 4.000-inch stroke. The engine uses comparatively tight bearing clearances of 0.0021-0.0023- inch for the mains and 0.0021-0.0022 for the rods. Tighter clearances generally help minimize high-rpm windage, for— — you got it— — better oil control.

“Their dyno is known to be pretty conservative,” Lohone says. “But they really know their stuff with these injection systems, so we’re very pleased with the numbers we achieved, while BES founder Tony Bischoff noted it was one of the best-performing street small-blocks they’ve tested.”

More than the sum of its parts and dyno numbers, this distinctive small-block build includes a number of unique features designed to support high-rpm valvetrain strength and stability, as well as oil control. For oiling, Lohone employed a dry-sump system that drastically reduces windage by limiting the amount of oil in the pan, which is a custom-built unit from Kevco, with a full-length, louvered windage tray. There are also a number of strategically located oil drains in the heads and lifter valley to feed directly to the oil pan.

Chamfering or “tear -dropping” the edge of the oil feed passage holes in the crankshaft journals reduces the shearing of the oil flow as it exits the passage, promoting enhanced oil flow for the crank journals and rod bearings that helps build up the oil-film cushion more quickly.

“It’s not just about the parts that generate the power, but the supporting components that help make the power sustainably and with long-tern durability,” Lohone says. “When you focus on the little things, such as optimizing the oiling system, the engine will perform better and live a lot longer.”

Those fine details are illustrated in the accompanying photos where the overall assembly and dyno testing are outlined. There’s a lot to learn here, from the build of what many would consider an archaic platform for building power, but with its LS/LT-challenging horsepower and torque production that neither modern engine family can touch, this old-school overachiever proves the small-block remains a viable and formidable performance option.

The crankshaft is located with splayed, four-bolt main caps— a feature built in to the Dart block and wasn’t available in a factory block. And, yes, the 1970-1972 LT1 engine had four-bolt mains, but they weren’t splayed.

ACP

ON THE DYNO
RPM TORQUE HORSEPOWER
3400 430 279
3500 451 300
3600 472 323
3700 488 344
3800 502 363
3900 531 394
4000 551 420
4100 558 435
4200 567 453
4300 578 473
4400 584 489
4500 580 496
4600 578 506
4700 578 517
4800 581 531
4900 590 550
5000 597 568
5100 605 587
5200 613 607
5300 614 620
5400 611 628
5500 605 634
5600 599 639
5700 594 644
5800 590 652
5900 586 658
6000 581 664
6100 580 674
6200 578 683
6300 576 692
6400 574 700
6500 571 707
6600 564 708
6700 555 708
6800 546 707
6900 537 706

Peak numbers in bold.

SOURCES
BES Racing Engines
(812) 576-2371
besracing.com

Valley Performance
(616) 522-9710
valleyperformancellc.com

The camshaft is a roller-type, with the larger, strength-enhancing base circle size of the big-block and specs including 0.757/0.758-inch lift, 254/264 -degrees duration at 0.050- inch, and a moderate 110-degree lobe separation angle that contributes to the engine’s broad powerband. It is installed straight up on a 109.5-degree intake centerline. It’s not the most aggressive cam to come out of the grinder, but that was intentional to ensure streetability.
When it comes to the rest of the rotating assembly, the components include forged Wiseco pistons, with friction-reducing skirt coatings, and K1 forged I-beam rods measuring 6.000 inches in length.
Along with a conventional Napier-style second ring and a 14-poundlb oil-control ring, the piston ring pack includes this 1/16-inch gapless and gas-ported top compression ring. The horizontal slots in the ring allow combustion gases to enter through the groove and behind the ring to improve ring sealing.
The cylinder heads are aluminum, 18-degree Edelbrock units that were CNC-ported by BES Racing Engines and flow 385 cfm through the intake ports.
Machined combustion chambers have a 66cc volume, contributing to a pump-gas-friendly 10.96:1 compression ratio (premium pump gas, that is). Also, the steel valve seats with a 50-degree seat angle.
A number of mods were made to the heads to support the engine’s unique oil control system, including an oil drain-back hole drilled into the rear of each head, which will feed directly to the oil pan via a -12 hose. That’s complemented with plugging the original front and rear drain holes with 1/4-inch pipe plugs and drilling 1/16 -inch in them to limit the oil draining back into the valley.
Valvetrain components include 2.200-inch intake and 1.600-inch exhaust valves, Trend 3/8-inch-diameter pushrods (8.3-inches long with 0.135-inch walls), and PAC Endurance dual-coil springs. The springs’ specs include a 2.050-inch installed height, 265-lbpound seat pressure, 663-poundlb open pressure, and coil bind at 1.150- inch.
A set of Fel-Pro MLS head gaskets helps seal the heads against the block. They’re 0.053-inch thick to accommodate a 0.010-inch positive piston deck height, for an ideal quench height (the distance between the piston and cylinder head) of 0.043- inch.
More valvetrain stuff here: A Jesel shaft-style rocker system with 1.6-ratio, aluminum-body roller rocker arms. Compared to the factory-style individual stud-mount design, the shaft design offers greater high-rpm stability and consistency, especially with higher spring pressures.
There was a figurative and literal rub with the Jesel rockers: They didn’t fit under the snazzy, finned aluminum valve covers purchased for the engine,. sSo, clearance holes were cut into them and bolt-on pocket covers were custom-machined to provide the necessary rocker room.
Here’s a look at the clearance required to use the valve covers with the Jesel rockers. The custom pocket covers did the trick.
The lifters are Morel solid rollers, with a bushing rather than roller bearings inside each roller. The lifter bores were over-bored to 0.937 -inch to accommodate an 0.850-inch roller versus the conventional 0.760-inch size— — a move made for increased valvetrain control and greater durability. The mod also included adding clearance to the lobes so that they wouldn’t interfere with the lifter bodies.
To eliminate a common small-block hotspot between the central exhaust valves, which can cause detonation or head gasket issues, coolant from the cold side of the cooling system is directed to a passage built into the heads. Builder John Lohone crafted pipe extensions that delivers the water directly to the hotspot rather than simply plumbing the water to the port, where it would dissipate and heat up quickly.
A wider shot here shows the routing of the cooling modification with a -4 hose, from the black-anodized spacer on the front of the engine between the block and -16 fitting for a remotely mounted electric water pump to the pipe fitting in the cylinder head, below the central exhaust ports. There’s a mirrored setup for the other side of the engine. Each water pump spacer was drilled and tapped to feed cold water to the heads.
There is a lot going on at the front of the engine, starting with the Jesel belt drive that was selected over a conventional timing gear for less harmonics and easier timing adjustments. Also: a Hall-effect crank trigger, which uses a more precise square-wave signal than a magnetic pickup, is used to provide the crankshaft speed and position signal to the Holley EFI control system. There is still a distributor on the engine, but it is used only for secondary ignition.
A magnetic pickup is used for the camshaft position signal. For it, a hole was drilled into the cam gear and bolt with a magnet on it was installed. The Holley sensor picks up the signal and sends it to the controller.
The pump for the dry-sump oiling system is a three-stage unit from Stock Car Products. The goal with it is to minimize oil in the pan in order to minimize or eliminate power-robbing windage at high rpm, while also offering better oil temperature control. It might be a little overkill for a street engine, but this one will also see track time, where such a system will come in handy.
A simple throttle -body–-style injection system with carburetor-style intake manifold would have been a simpler, cheaper alternative, but this Kinsler individual -runner–-type system simply looks bad-ass and it has that vintage racing look that will look perfect in the replica Cheetah race car. The bore diameter for each stack is 2-7/16- inch, so the system has the capacity to flow a lot of air into the engine.
Each runner manifold bolts directly to its corresponding cylinder head, along with a separate valley cover plate. That means there is no common plenum for the controller to draw a vacuum signal for the MAP (manifold absolute pressure) sensor. That’s solved by running a vacuum line from the base of each runner and joining them in a common log, which connects with another line to the MAP sensor.
Another set of larger vacuum lines is routed from each runner to an aluminum junction box fitted with the necessary IAC (idle air control) valve. It regulates airflow to maintain a smooth, steady idle between 950 and 1,000 rpm. The “sock” seen in the photo is protection for the valve’s air filter.
Fuel delivery comes via a set of injectors rated at 47.8 lb/hr at 45 psi. In this application, the fuel pressure regulator is set at 58 psi, and the injectors are fired sequentially.
Generally, small-block Chevy engines run best with around 34-38 degrees of total timing, but this combination did the best with a more conservative 32 degrees and pushing it to 33 degrees delivered no gains in dyno testing, so 32 degrees was deemed the sweet spot for efficient combustion and peak power: 708 horsepower at 6,600 rpm and 614 lb-ft of torque at 5,300 rpm. More impressive is that the engine topped 500 lb-ft by only 3,800 rpm. It’s big-block grunt in a small-block package. By the way: The test used 1-7/8-inch -to- 2-inch stepped headers, with an average primary length of 35.75 inches and 3.5-inch collectors.
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