UPDATE, November 5: The most powerful crate engine in Chevrolet’s parts catalogue has been shown off on the dyno, providing a thumping soundtrack.

Making its peak power up at 6600rpm, the 10.3-litre pushrod V8 starts off sounding like any other Big Block Chevy, but progressively gets louder – and seemingly smoother – as the revs rise, with not even a hint or rasp or wail from its headers.

For such a large displacement engine, it’s impressive for Chevy to tune it to make peak power so high up in the rev range, let alone cap it at a limit of 7000rpm.

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November 4: Chevrolet’s latest addition to its big-block crate engine range is the biggest and most powerful yet.

The new donk is codenamed ZZ632/1000 (translating to 632ci, 1000hp), with the 10.3-litre big-block quoting figures of 1004hp (748kW) and 876ft/lbs (1187Nm) straight out of the box on pump fuel.

The new iron-block 632 is based on the existing ZZ572 (572ci) Chev crate engine, but with some additional tweaks.

The aluminium heads are a brand new piece of kit – CNC-machined 70cc high-flow units Chevy has called RS-X Symmetrical Port heads.

As the name suggests, both the intake and exhaust ports are all symmetrically ported, keeping power consistent across all eight cylinders.

The RS in RS-X stands for Ron Sperry, the company’s engineer responsible for designing the new heads and the same man who gave us the original symmetrically-ported heads found on the legendary LS1.

Former Hot Rod Magazine editor and Motortrend video presenter David Freiburger weighed in on the new mill, saying in an Instagram post: “It looks a lot like LS head tech applied to a Rat motor. I’m pumped about it – especially that GM is interested in developing aftermarket gasoline engines at this level.”

Internally, the 632 uses a forged steel crank and H beam rods, as well as aluminium pistons and four-bolt main caps. The 632 uses a billet steel hydraulic roller camshaft, with specs of valve lift (in.): 0.780 intake/0.782 exhaust, with a duration of (@0.050 in.) to equal 270º intake/287º exhaust.

The bore has grown by 0.040 of an inch, and stroke has increased by 0.375 over the 572 crate engine to gain the extra displacement.

Those figures may have you thinking this will be a low comp, low-revving, lazy donk – but that certainly isn’t the case. Not only is compression kept at a decent 12.0:1 (impressive for pump fuel), but Chevy says peak power is delivered at 6600rpm and the 632 is recommended to rev to 7000rpm.

Eagle-eyed readers will also spot the addition of injection to the high-rise single-plane manifold, which appears to be a first for a GM big-block crate motor – given both of its current 572 units (621hp and 727hp variations) are sold with carburettors.

Another LS-like addition for the 632 is crank-triggered, coil near-plug ignition. It further modernises the 632 over its smaller 527 siblings, which use a traditional distributor for spark.

Chevy subjected a test mule to 200 simulated drag strips run on an engine dyno, so its intentions for this new donk are pretty clear – this is a race engine, not a towing one.

The new mill is a welcome relief for Chevy fans, after the company recently canned its supercharged LT5 crate engine as it slowly transitions towards electric power across the entire vehicle range.

The ZZ632 will be on display at SEMA on November 2-5, 2021, with US deliveries expected to begin in early 2022.

Pricing in the US has been confirmed, with The Drive reporting a MSRP of US$37,758 (AU$50,782).

That makes the 632 GM’s most expensive crate motor by a fair margin, with reports saying the slightly smaller 572 big block can be had for around US$16,000 (AU$21,518.83) in 727hp form.

We’ve also contacted GM for an official word on the 632 being offered locally and pricing, and are awaiting a response.