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In the world of classic European performance, few engines are as iconic—or as deceptively complex—as the air-cooled flat-sixes from Porsche’s lineage. And this week’s standout engine build from Engine Lab of Tampa is a masterclass in blending old-school precision with modern performance demands.
We met up with shop owner and veteran engine builder Rokket Horton, who walked us through a 1986 3.2L Porsche 911 engine undergoing a transformation into a 3.4L RS-inspired powerhouse. Originally built by Horton a few years ago, the engine returned to the shop for one simple reason: more power.
“There’s nothing wrong with it mechanically,” Rokket explains. “The customer just wanted more out of it—and with these, you don’t just throw a chip in and call it a day.”
Beyond EFI: The Art of Air-Cooled Power
While this generation of flat-six does feature electronic fuel injection, tuning options are limited. Horton’s answer? Classic hot-rodding: displacement, airflow, and compression.
“Where you make the power is in porting and removing resistance in the intake,” says Horton. “We’re going to port this thing until it’s silly—you could fit a Coke bottle in there.”
The engine is receiving what Horton calls an “RS conversion,” a nod to the legendary Porsche RS series that dominated motorsport from the early ‘70s through the late ‘80s—winning at Sebring, Daytona, and Le Mans.
No Replacement for Displacement
The heart of the build lies in a bump from the factory 3.2L to a 3.4L configuration. This was achieved by swapping in Mo Motorsports RS-series cylinders, which are two to three millimeters larger in bore than stock.
“Going to 3.4L doesn’t require case machining,” Horton explains. “But if you go 3.6, then you’ve got to split the case halves and bore them out. That’s a much bigger job.”
The pistons are 10.5–10.7:1 compression Mahle Motorsport units with a distinctive shape. “Porsche hemispherical heads have been around since before hemis were cool,” Horton notes.
Precision Assembly, No Room for Error
Porsche’s composite engine design means each cylinder is standalone. “If you have a catastrophic failure in one cylinder, you can just replace that one—it’s all modular,” Horton says. But modular doesn’t mean forgiving.
“These engines require finesse and measurement. You don’t just line up timing dots like on a small-block Chevy,” Horton says. “Everything is dial indicators and feeler gauges. Cam timing, for example, comes down to getting a pin set for overlap—exactly 1.239mm, in this case.”
The overlap figure refers to the precise moment both intake and exhaust valves are open for scavenging—a critical detail for performance and emissions. And because camshaft timing is locked via pins instead of bolts, there’s no room for guesswork.
No Gaskets, No RTV—Just Experience
Unlike most engines, air-cooled Porsche engines don’t use traditional head gaskets. Precision machined fitment does the sealing. In boosted applications, O-rings or flame rings (Iris rings) are sometimes added—but this engine remains naturally aspirated.
One of Horton’s biggest cautions is about improper sealing techniques.
“I’ve seen more Porsche failures from people using RTV than anything else,” he warns. “These engines need anaerobic sealants like Loctite 574. Use the wrong stuff and you block oil spray bars, wipe out the cams, and it’s game over.”
From 1986 to 2025—Power the Old-School Way
Back in 1986, the stock 3.2L made around 245–250 hp, limited heavily by emissions equipment like thermal reactors and catalytic converters. Once Horton’s done with this 3.4L RS conversion, it’s expected to push nearly 400 horsepower—all-motor.
The customer? A dual Porsche owner who already has a track-prepped GT3. This build, though, is for the street.
“This one’s for date night,” Horton laughs. “Pull up next to a Mustang, and maybe hurt some feelings.”
Final Thoughts
This air-cooled Porsche build is more than just a nod to the past—it’s a reminder that performance isn’t always about turbos or ECUs. Sometimes, it’s about displacement, discipline, and a deep respect for mechanical craftsmanship.
And for Rokket Horton, it’s all in a day’s work.
Engine of the Week is sponsored by PennGrade1 and Elring – Das Original. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at [email protected].
