EJR Performance-built 434ci Clevor combo

The news might be full of doom and gloom, but we can take heart that we live in an epic era for horsepower, as this 434ci Clevor combo from EJR Performance proves. Sucking through a single Holley carb with a hydraulic-roller cam, this small-block Ford thumps out 710hp at 6500rpm, and EJR’s Ed Johnson says he designed it to be as simple as possible.

First published in the July 2025 issue of Street Machine

“I wanted to cater to guys who want a good, reliable street car engine that doesn’t need big maintenance or to have the valve covers off every weekend,” Ed says. “We developed it with the team at Cylinder Head Innovations [CHI], as they’d always wanted to see if their 225cc heads could make 700hp naturally aspirated with a roller cam.”

Based around a 9.5in-deck-height Dart block, the bottom end swings a Scat crank, Callies rods and 11.8:1 RaceTec pistons. While it is a four-bolt layout, the main caps are still steel rather than billet alloy. “We played around with the pin height on the pistons, but it isn’t a radical difference, as nothing in this combo is out of the ordinary,” says Ed. “I wanted to strip everything back and not have any exotic porting or machining done to make the power.”

In keeping with that ethos, the wet-sump oil system is also comprised of standard street-car parts, including a Moroso sump.

“Really, the biggest trick with this engine was switching to LS valve springs,” Ed says. “There is no magic in this one, and I don’t mind sharing what we did, because everyone benefits from learning about what works. I actually played around with a quad-pattern cam, but we came back to a more conventional design.”

That bumpstick is a hydraulic-roller measuring 244°/256° with 660thou lift on a 108° LSA. It works Johnson lifters and Scorpion rockers in the 225cc CHI raised-port heads.

The Holley XP 950cfm carb is mounted on an Unrivaled Engineering spacer above a CHI single-plane intake, and Ed reckons it was a cinch to get it running hard. “The Holley 950 needed minimal adjustments to get the power; it was very impressive,” he says.

The black-anodised distributor is a new offering from ICE Ignition in Melbourne, working with an ICE coil pack mounted to the front of the Clevor on an Unrivaled Engineering bracket.

“All the front ancillaries, including the carb spacer, serpentine pulleys, lead separators, throttle cable, alternator and coil brackets, are Unrivaled Engineering products, which I also make,” says Ed. “I’ve developed these to hopefully improve some of the problems people were having with off-the-shelf parts in the past. When I developed the Unrivaled Engineering alternator bracket, I added the tensioner to it.”

While the Clevor’s 700hp and 600lb-ft output is super-impressive with the unported CHI heads, Ed is now developing the combo further with a 4.100in stroke to push 444ci, using 220cc CHI heads.

“This is engine isn’t going into a car; it was purely an R&D engine, and now it’s going to be for sale,” Ed says. So, if you have a project that could make use of a genuine 700hp street engine, get in touch with Ed at EJR Performance.

PUMP UP THE JAM

Impressively, Ed made the 700hp target using pump unleaded, but it wasn’t premium 98 RON. “We did it with 95-octane fuel,” he laughs. “The issue with 98 is that the additional octane slows the burn, which works against carburettor motors and often costs horsepower.”