Australian closed-chamber 2V heads vs US open chamber
within 1% of peak across that whole range
Engine dyno, as configured — flywheel horsepower. Standard test config: stock manifolds through 18" of pipe, air cleaner lid flipped, no accessories driven. Factory SAE net ratings are measured as‑installed and read 15–25% lower. Rev ceiling for this combination: 5900 rpm.
Where each one wins
| RPM | US open 2V | Aussie closed 2V | diff |
|---|---|---|---|
| 2000 | 328 | 333 | +6 |
| 2500 | 349 | 355 | +6 |
| 3000 | 369 | 376 | +6 |
| 3500 | 385 | 391 | +7 |
| 4000 | 387 | 394 | +7 |
| 4500 | 369 | 375 | +6 |
| 5000 | 334 | 340 | +6 |
| 5500 | 297 | 303 | +5 |
| 6000 | 230 | 234 | +4 |
Torque, lb-ft, at the flywheel. Everything except the part named is identical between the two runs.
Ford Australia kept building Clevelands after Ford US quit, and their 2V head has a 58cc closed chamber where the American one has 75cc wide open. Same ports, same valves, same flow numbers.
All of the difference is chamber. On identical pistons that is over two points of compression, plus real quench. It is the single best-value head swap on this engine and it is why people import them.
They are getting harder to find and the prices show it. Check what a set actually costs before you plan a build around them.
The build
| Block | Factory 351C 2-bolt main (stock) |
|---|---|
| Crank | Stock cast iron — 3.50" stroke (351 ci) |
| Rods | Stock I-beam (factory) — builders' guide ~450 HP |
| Pistons | Generic flat top (0cc) |
| Head gasket | OEM compressed (.040") — neutral |
| Cylinder heads | 2V US open chamber (75cc) — the common head |
| Porting | As-cast / stock |
| Camshaft | COMP XE262H — hyd flat (32-242-4 · 218/224 @.050 · .513"/.520") |
| Valve springs | COMP 987-16 dual |
| Rocker arms | Stock stamped 1.73 rockers |
| Intake manifold | Edelbrock Performer 351-2V #2750 — 4bbl flange, 2V ports |
| Carburetor | Holley 600 cfm 4150 |
| Exhaust | Long tube 1-5/8" — street |
| Ignition | Pertronix Ignitor II — hotter spark · ~7,000 rpm |
| Fuel | Sunoco 260 GT Plus 104 — unleaded, 13% ethanol |
| Air cleaner | Stock air cleaner, LID FLIPPED — DYNO STANDARD |
These numbers assume a proper dyno tune — timing and jetting set on a dyno, not guessed at in a driveway. It is worth 13 hp on this combination, and it is the one line on this page you cannot buy: we build the parts list, you pick the tuner. Leave it untuned and the engine will run, it just will not read what it says up top.
The other one
| Block | Factory 351C 2-bolt main (stock) |
|---|---|
| Crank | Stock cast iron — 3.50" stroke (351 ci) |
| Rods | Stock I-beam (factory) — builders' guide ~450 HP |
| Pistons | Generic flat top (0cc) |
| Head gasket | OEM compressed (.040") — neutral |
| Cylinder heads | 2V Aussie closed chamber (58cc) — quench, the 2V to have |
| Porting | As-cast / stock |
| Camshaft | COMP XE262H — hyd flat (32-242-4 · 218/224 @.050 · .513"/.520") |
| Valve springs | COMP 987-16 dual |
| Rocker arms | Stock stamped 1.73 rockers |
| Intake manifold | Edelbrock Performer 351-2V #2750 — 4bbl flange, 2V ports |
| Carburetor | Holley 600 cfm 4150 |
| Exhaust | Long tube 1-5/8" — street |
| Ignition | Pertronix Ignitor II — hotter spark · ~7,000 rpm |
| Fuel | Sunoco 260 GT Plus 104 — unleaded, 13% ethanol |
| Air cleaner | Stock air cleaner, LID FLIPPED — DYNO STANDARD |
These numbers assume a proper dyno tune — timing and jetting set on a dyno, not guessed at in a driveway. It is worth 13 hp on this combination, and it is the one line on this page you cannot buy: we build the parts list, you pick the tuner. Leave it untuned and the engine will run, it just will not read what it says up top.
Change these numbers yourself