How to make 400 hp from a 351 Cleveland
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: 6000 rpm.
Four hundred is the number people ask for more than any other, and on a Cleveland it does not take a stroker or a race cam. It takes flat tops, a hydraulic cam that actually uses the head, an aluminium dual plane, long tubes, and springs that let it rev.
The springs are the part everyone skips. With the factory 2V springs still in place this same parts list stops breathing at 4,800 rpm and gives back most of what the cam paid for.
This is a stock two-bolt block with stock rods, and that is fine here — factory I-beams are generally happy to around 450. Past that the rods become the honest limit, not the heads.
The build
| Block | Factory 351C 2-bolt main (stock) |
|---|---|
| Crank | Eagle forged 4340 — 3.50" stroke / 351 ci (~$700) |
| Rods | Stock I-beam (factory) — to ~450 HP |
| Pistons | Generic flat top (0cc) |
| Head gasket | OEM compressed (.040") — neutral |
| Cylinder heads | 4V open chamber (75.6cc) — 70s CJ/Q-code |
| Porting | As-cast / stock |
| Camshaft | COMP XE274H — hyd flat (32-246-4 · 230/236 @.050 · .562"/.565") — Holdener +44 HP vs Boss cam |
| Valve springs | COMP 916-16 dual |
| Rocker arms | Stock stamped 1.73 rockers |
| Intake manifold | Edelbrock RPM Air-Gap |
| Carburetor | Holley 750 cfm — street/strip sweet spot |
| Exhaust | Long tube 1-3/4" — hot street |
| Ignition | Pertronix Ignitor II — hotter spark · ~7,000 rpm |
| Fuel | Pump 93 octane |
| Air cleaner | Stock air cleaner, LID FLIPPED — DYNO STANDARD |