Video: All-Aluminum 598 Cubic-Inch Big-Block For The Street

Video: All-Aluminum 598 Cubic-Inch Big-Block For The Street

Big-block engines seem to perform effortlessly well on the street, thanks to the big displacement and big torque inherent to their design. So, when Jake Gibbons of Gibbons Motorsports told Jeff Huneycutt of The Horsepower Monster he was building a big-block for himself, there was next to zero chance we wouldn’t be seeing a video of the project.

Since Huneycutt is a big-block fan, he was incredibly excited to follow Gibbons’ journey to put together a rowdy 598-cube big-block Chevrolet engine for his C10 pickup truck. Originally, the plan for the engine was for something primarily with incredible street manners. However as engine builders are wont to do, the build spiraled to something more aggressive.

The Core Of The Matter

Since part of the goal was a lightweight engine, a tall-deck (10.200 inches) aluminum Brodix block was chosen as the foundation for the engine. However, when the block showed up, it had a larger bore than originally intended, at 4.600 inches. The block’s billet main caps, strengthening webbing, and .938 lifter bores certainly lend themselves to racier parts usage as well.

The crankshaft is a 4.500-inch-stroke forged Callies piece, that is fully counterweighted. Besides profiling the counterweights’ leading edge, the crank has been coated to help shed oil and reduce windage. Clevite coated bearings along with ARP main studs and beefy main cap dowels hold the crankshaft in place. All five main caps are four-bolt designs, but the inner three caps feature splayed outer studs (not bolts).

big block chevy

The fully counterweighted Callies crankshaft will not only be stronger than a six-counterweight design, but will also perform better at high RPM.

Attached to the crankshaft are Molnar forged-steel H-beam connecting rods measuring 6.535 inches, center-to-center. Gibbons took an extra step, sending them to Calico Coatings to be super finished. Clevite coated bearings are used in the rods as well.

The pistons are custom 4.600-inch diameter 2618 pieces from JE Pistons. A skirt coating has been added to help eliminate cylinder scuffing. The flat-top design only has a single intake valve pocket with enough compression height to keep the wrist pin out of the oil ring. A 1/16-inch, 1/16-inch, 3/16-inch ring pack will reliably seal the cylinders.

A Melling Select Series billet aluminum oil pump integrates the pickup into the billet pump housing for a one-piece unit. A fabricated aluminum oil pan from Dan Olsen, with a deep sump, asymmetric windage-reducing kickouts, and clearance for the splayed four-bolt mains is used. The rear-sump design is aimed at first-gen Camaros and should fit the C10 nicely.

big block chevy piston

The 4.600-inch JE pistons slugs are on 6.535-inch Molnar H-beam rods. The flat-top crown with only a single intake valve relief should allow for a 10.1:1 compression ratio.

The camshaft is a custom grind from COMP Cams. Gibbons opted for a 55mm-core solid roller with .426 inch of lobe lift on the intake and .430 inch on the exhaust. Duration at .050 is 256 degrees on the intake and 263 degrees on the exhaust, with a 110-degree lobe separation angle. Using 1.7:1 ratio rocker arms, that will be .724 inch of lift at the valve on the intake side and .731 inch at the exhaust valve.

The camshaft also has a different firing order ground into it, opting to use the LS engine family’s 1-8-7-2-6-5-4-3. Riding on the lobes are a set of .938 solid-roller tie-bar lifters from Crower. Gibbons opted for a bushed roller design instead of the more traditional needle bearings. Handling the camshaft timing is a Jesel belt drive. The two-piece upper pulley offers infinite adjustment of up to 10 degrees of camshaft advance or retard. An ATI Super Damper rounds out the short-block.

firing order swap cam

The cam for this engine is unique in that it has switched to the LS engine family’s 1-8-7-2-6-5-4-3 firing order.

24 Degrees Up Top

Topping off the combo is a set of Brodix 24-degree fully CNC-ported big-block heads. The oval intake runners measure a massive 365cc and flow 460cfm. The valves are 11/32-inch stainless-steel Rev pieces measuring 2.350 inches on the intake and 1.880 inches on the exhaust. The intake valve seats have been recut to a 50-degree angle to improve high-lift flow.

The cylinder heads have a fully machined 119cc combustion chamber, which makes for a pump-gas friendly 10.1:1 final static compression ratio. PAC Racing Springs dual valvesprings control the valves with a 629lb/in spring rate and will handle up to .850 inch of lift. As installed, they offer 280 pounds of seat pressure and 735 pounds of open pressure. Titanium retainers and steel locks keep everything together.

In order to translate cam motion into valve motion, a set of 1.7:1 aluminum Jesel rocker arms are employed. The Jesel system uses a single rocker stand of the intake valve rocker arms, and individual stands for the exhaust rocker arms, that also screw into the main stand. The pushrods are large 7/16-inch, .125 wall pieces from Trend Performance that measure 9.050 inches long for the intake and 9.825 inches on the exhaust.

On the left you can see the fully CNC-machined 119cc combustion chamber housing a 2.350-inch intake valve and 1.880-inch exhaust valve. On the right, the 1.7:1 Jesel aluminum rocker arms use a single stand for all the intake rockers, and separate stands for each exhaust rocker arm.

Topping off the big-block combination is Brodix’s large single-plane 4500 cast intake manifold. Gibbons massaged the interior of the plenum by hand for a little extra performance. A Super-Sucker four-hole tapered carb spacer from HVH adds a little plenum volume and sits between the manifold and the Holley Sniper Stealth 4500 throttle body injection unit. Equipped with eight 100 lb/hr fuel injectors, the Stealth 4500 can handle up to 1,500 horsepower, naturally aspirated.

To complement the modern electronics in the Stealth 4500 system, Gibbons opted for an MSD Distributorless Ignition System. The aftermarket coil-per-plug setup is similar to that found on LS engines (in fact, the coil mount bracket is for an LS engine) with a cam position sensor taking the place of the rear-mounted distributor.

(Left) The Holley Sniper Stealth 4500 EFI system has all of the electronics packed into the throttle body, along with the eight 100 lb/hr fuel injectors, to support up to 1,500 horsepower N/A. (Right) The MSD DIS system converts the big-block powerplant to a coil-per-plug setup, allowing for hotter spark, shorter wires, and a lot more ignition tunability.

On The Dyno

Once everything was hooked up on the dyno, the team decided to program the Stealth 4500 entirely through the 3.5-inch handheld touchscreen programmer. In fact, the only time the laptop was used was for some data monitoring during the dyno pulls. The Holley was set into self-learning mode and allowed to get its bearings on 93-octane pump gas.

With the sweep set fo 3,800 rpm to 6,600 rpm, the engine was loaded and the button pressed. At the end of the pull, the team was rewarded with 802.7 horsepower at 6,200 rpm and 742.6 lb-ft of torque at 5,200 rpm. Of note is that the torque broke the 600 lb-ft mark at 4,000 rpm, and never dropped below that point throughout the rest of the run. Gibbons believes that there is more to be had out of the cylinder heads with a little more duration from the camshaft.

As expected, 598 cubes at 10.1:1 compression made a ton of torque. Besides the peak numbers of 802 horsepower and 742 lb-ft of torque, the curves are awesome for a street car.

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About the author

Greg Acosta

Greg has spent seventeen years and counting in automotive publishing, with most of his work having a very technical focus. Always interested in how things work, he enjoys sharing his passion for automotive technology with the reader.
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