If you could go back 50 years and tell legendary small-block Chevy guru Bill ‘Grumpy’ Jenkins that in 2026, you’d be able to order a 650hp Chev mouse motor as a package off something called ‘the internet’, he’d no doubt look at you like you were chasing pink elephants. Yet that’s the world we live in today, as this 650hp, 568lb-ft combo from BK Race Engines proves.

First published in the April 2026 issue of Street Machine

Having somewhat fallen out of favour a quarter-century ago, traditional street machining engines like Chevrolet’s Gen 1 small-block are now experiencing a resurgence in popularity, which has driven some wicked development.

“You think old-school small-blocks are done because people are so focused on LS stuff, but there are still a lot of people out there building Toranas and muscle cars who don’t want one,” says BK’s Bill Kaglatzis. “Also, the days of a cheap, good, second-hand LS are over, and you’re not buying brand-new, running LS mills for $3000 anymore.”

This mouse motor packs 422ci thanks to a 4.155in bore and 3.875in stroke in a Dart SHP block. A Scat 4340 crank and H-beam rod combo work custom RaceTec pistons for pump fuel-friendly 12:1 comp. A custom BK-spec Bullet mechanical roller cam, BAM bushed lifters, 3/8in Smith Brothers pushrods, and Yella Terra rockers round out a stable and rev-friendly valvetrain.

“This will go to 7000rpm no worries,” Bill says. “It’s going into a tough street Torana that is a bit of a weekend warrior that’ll do some drag racing.”

While this engine uses traditional 23-degree AFR 210cc heads, the BK team has since discovered a handy upgrade. “Since this small-block, we’ve done two other similar engines with the larger AFR 227cc heads,” says Bill. “At $500, the upgrade is virtually the same cost, but with those bigger heads, the combo will go to nearly 700hp. One did 694hp and 585lb-ft.”

Don’t go looking for drive-by-wire anything on this small-block. Perched high on the Trick Flow intake and Black Widow spacer is a twin-blade APD carburettor that flows a huge 1000cfm like a 4500 Dominator carb, but still fits the 4150-pattern intake manifold. “The intake didn’t need any work to make this power; it’s great out of the box,” says Bill.

Despite being the Heartbeat of America, this small-block Chev uses some killer Aussie parts in key areas. The life-giving oil is held in a custom ASR pan; an ICE Ignition distributor throws the sparks; and a Romac balancer and Rollmaster timing chain keep everything synced.

“This engine is more of a traditional package for a classic muscle car,” says Bill. “We have a more powerful package for the small-block platform that does 775hp, but it uses an 18-degree cylinder head instead of the old 23-degree format.

“We’ll keep looking for gains in all our combos, though. Years ago, we’d have never thought we’d be talking about 650hp as a basic street engine.”

’TRAIN OF THOUGHT

Despite making V8 Supercar power levels and being capable of 7000rpm, the Chev’s valvetrain is nothing exotic. There are no roller bearing cam tunnels or five-digit-horsepower components, just quality hardware used in-spec, including shaft-mount, 7/16in Yella Terra Platinum alloy roller rockers, Crower valve locks, and PAC valve springs.

BK Race Engines
Bankstown, NSW
bkraceengines.com.au