If the popularity of specific videos is any indication, enthusiasts love high-rpm motors. Look no further than Formula 1 for examples – who doesn’t love to hear the shriek of a high-rpm, small-displacement motor at full song? When sanctioning bodies give engine builders displacement limits, they make up for the lack of cubes with engine speed.

Typically, high-rpm race engines tend to combine big bores with short strokes, for a number of reasons. The first consideration is piston speed, as a shorter stroke reduces piston speed by limiting the distance traveled over a given period of time. Perhaps even more important from a power standpoint is the fact that a short stroke and big bore helps further improve head flow. Bigger bores allow bigger, unshrouded valves which in turn equates to more flow. More flow equates to more power, especially at higher engine speeds.

By contrast, small bores limit head flow by shrouding the valves, so most race engine builders seek to maximize bore size for flow and then reduce stroke for rpm potential. Chevy applied this big-bore/short-stroke formula in the late 1960s when designing a production motor for the original Trans Am series, which dictated a maximum displacement of 5.0 liters. The 4.0" bore of a 327 block combined with the 3.0" stroke of a 283 crank gave us the legendary DZ302 that powered the first generation Camaro Z/28.

It was with this original formula in mind that we decided to build a big-bore, short-stroke LS motor using a factory block and crank. Unfortunately, the LS family didn’t offer the same bore and stroke combination as the original DZ302. The LS did offer a 4.0" bore 6.0L block, but there was no production 3.0" stroke crank. While duplicating the original DZ302 would have been cool, the production LS family still allowed us to combine a big-bore block with a short-stroke crank.

Looking over the myriad of LS combinations offered by the factory, the obvious choice for a crankshaft was the 4.8L LR4. Unlike the larger 5.3L, 6.0L and 6.2L, which all shared the same 3.622" stroke, the smaller 4.8L offered a shorter 3.267" stroke. Note that this stroke almost matches the 3.25" stroke length used in the original 327 Chevy.

For most enthusiasts on a budget, the cheap-date combo would be to simply build the 4.8L with a head, cam, and intake package optimized for high rpm. Unfortunately, the 4.8L was also saddled with a small 3.78" bore, which might otherwise restrict potential head flow and ultimately hurt power production. Another option would be to combine the 4.8L crank with a 4.0" bore 6.0L iron block. The 6.0L block would certainly work, but for our build, we decided to go even bigger.

For this 8,000-rpm LS, we combined the 3.267" stroke of the 4.8L with a 6.2L, (LS3) 4.065"-bore block. The new big-bore, short-stroke LS combo was sporting right at 340 cubic inches, thanks to a 4.070" overbore. Dropping the 4.8L crank into the LS3 block required use of custom JE pistons and 6.30" 4340 forged-steel connecting rods from Lunati, instead of the stock 6.275" 4.8L rods. The JE forged, asymmetrical pistons featured small, 5cc domes to increase the static compression ratio to 11.7:1 with our 58cc heads.

The short block was assembled using Fel Pro race bearings, timing chain and oil pump along with a Moroso oil pan, pickup and windage tray. Finishing things off was a custom cam from Brian Tooley Racing. The custom BTR cam offered a .627/.596 lift split, a 243/262-degree duration split and 110-degree (+5) lsa. The cam was teamed with a set of Crane hydraulic roller lifters that featured heat-treated and carburized 8620 steel with precision machined bodies and internal components that allowed them to run safely at 8,000 rpm and beyond.

The big-bore, short-stroke combo was now ready for a suitable induction system. Knowing that 8,000 rpm required plenty of head flow, we topped the short-stroke LS3 with a set of AFR LSX 230 V2 heads. As indicated by the name, the 230cc intake ports flowed 324 cfm, while the exhaust flow checked in at an equally impressive 252 cfm. Credit for the impressive flow numbers went to CNC porting combined with a 2.08/1.60 valve package. The 58cc combustion chambers helped further improve power by increasing the static compression ratio with our combination of displacement and piston design.

Naturally the AFR heads featured a valve spring package capable of supporting the desired rpm, while the BTR lobe profile offered the necessary stability. The head flow offered by the AFR LSX 230 heads was teamed with a Holley Hi-Ram intake manifold. The versatile Hi-Ram is available with a variety of different tops, so we configured the tunnel-ram style Hi-Ram with a dual-quad top designed to accept a pair of Holley 950 Ultra XP carburetors. Additional components used in this 8,000-rpm build included an ATI Super Damper – a critical upgrade at this engine speed – a set of 1 7/8-inch headers from American Racing Headers, and a Holley Dominator EFI system to control ignition timing.

Before running the motor in anger, we subjected the new big-bore, short-stroke combo to the necessary break-in cycles. Unlike older flat-tappet cams, both hydraulic and solid, there was no need to break-in the billet roller cam and hydraulic roller lifters. But we did want to provide some time to allow the rings to seal properly against the freshly machined bores. After the break-in process, we changed to Lucas 5W-30 synthetic and were free to rev this baby up.

After dialing in the timing with the Dominator and making a few jet changes to the XP carbs, the little monster showed it was ready and willing to rev. After tuning and a few pulls up to 8,000 rpm, the combo posted some impressive numbers. Thanks to the breathing offered by the big-bore and the top-tier induction system, the short-stroke, 340-inch motor produced peak numbers of 607 hp at 7,900 rpm and 466 lb-ft of torque at 6,200 rpm.

More than a few Westech customers walked over to the dyno room when they heard us zing this motor to 8,000 rpm. There really is something special about hearing an engine rev for all it's worth. Sure, a bigger motor could likely do the same thing, and might even make power doing it, but that certainly won’t diminish the popularity of this destroked LS3.