How to make 400 hp from a 351 Cleveland
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: 6000 rpm.
The proof that 400 does not need a stroker is Lykins Motorsports' 1970 351C 4V, dynoed at Dale Meers Racing Engines in August 2023 with the sheet on camera: 433 hp at 5,600 and 428 lb-ft at 4,000, on pump gas, at under 10:1, with untouched factory 4V heads and the factory cast-iron 4V intake. The only modern parts were a mild custom hydraulic roller, a one-inch phenolic spacer, and a carburetor built for the engine.
That is the whole lesson of this page in one dyno sheet. The 4V head is not the limit at 400. The iron intake is not the limit at 400. What the engine wanted was a cam that uses the port, springs that let it rev, and a tune. The build below gets there with parts you can order today instead of a custom grind, which is why it lands a little under Lykins' number rather than on it.
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) — builders' guide ~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 |
On this one the tune is worth about 17 hp, and most of it is jetting. A 750 on a 4V Cleveland runs rich out of the box; the jet change is cheaper than any part on this page. Source: Lykins Motorsports, 1970 351C 4V dyno results (SuperFlow, STD corrected 29.92"/60°F).
Change these numbers yourself