What a 351 Cleveland Actually Makes: Six Dyno-Verified Builds

Ask what a 351 Cleveland makes and you will get a decade of forum guesses. These are not guesses. Every number below came off an engine dyno, in a video or article you can go watch, with the combination spelled out. They are the same numbers this site's simulator is calibrated against, which is why the tool gives you an answer instead of a fantasy.

One thing to keep straight before the numbers: correction factor. STD (standard, 29.92 inHg dry, 60°F) and STP read a few percent apart, and SAE reads lower still. A shop quoting SAE and a shop quoting STP on the same engine can be 15 horsepower apart with nothing changed. Each build below is labeled.

1. Factory 4V, stock heads, stock iron intake — 433 hp

1970 351C 4V. Untouched factory 4V heads, factory iron 4V intake, mild hydraulic roller, under 10:1 compression. 433.5 hp @ 5,600 / 427.7 lb-ft @ 4,000. STD. (Lykins Motorsports, dyno operated by Dale Meers.)

This is the one that surprises people. No porting, no aluminum intake, no big cam, compression in the nines — and it still makes better than 430. The Cleveland's factory 4V port is enormous, and once you put even a modest hydraulic roller in front of it, it flows enough to carry a real number. Note the torque peak at 4,000 and how flat that engine is underneath: this is a perfectly usable street combination.

2. Boss 351 replica — 383 hp

Factory-style Boss 351 build: closed-chamber 4V heads, Boss solid flat-tappet cam (290/290 advertised, .477 lift, 116 LSA). 383 hp / 391 lb-ft. (Richard Holdener.)

Ford rated the 1971 Boss 351 at 330 gross horsepower. On a modern dyno a faithful replica lands in the low 380s. It is a genuinely good engine and a piece of history — but as build number 3 shows, the cam is what is holding it back, not the heads.

3. Same engine, modern hydraulic cam — 451 hp

Factory 4V heads, Edelbrock Performer RPM intake, COMP XE284H hydraulic flat tappet (240/246 @ .050, .584/.588 lift, 110 LSA). 451 hp / 411 lb-ft. STD, SuperFlow. (Speed Secrets.)

Same short block as the Boss-cam test. One camshaft. +54 horsepower. If you own a Boss 351 and you are not required to keep it numbers-correct, this is the cheapest 50 horsepower available to you.

4. Air-Gap and the same cam — 450 hp

351C, Edelbrock Performer RPM Air-Gap, COMP XE284H. 450.4 hp / 411 lb-ft. (Richard Holdener.)

Two different dynos, two different engines, the same cam and intake class, and the results land within one horsepower of each other. That is what a trustworthy anchor looks like, and it is why the 450-hp mark is the realistic ceiling for a well-sorted iron-head 351 on pump gas with a hydraulic flat tappet.

5. 408 stroker, iron heads — 588 hp

408 cubic inches. Tongued iron 4V heads flowing roughly 350 cfm, Scott Cook intake, Pro Systems 780 carburetor, solid flat-tappet cam. 588.5 hp @ 6,700 / 536.4 lb-ft @ 4,800. STP. (Competition Engines.)

Stroke the Cleveland to 408 and the big 4V port finally has enough displacement under it to justify itself. Note that this is still an iron-head engine on a flat tappet — no aluminum heads, no roller. Nearly 600 horsepower out of a factory casting is what the Cleveland has always been capable of and what its reputation is built on.

6. 354 solid roller — 615 hp

354 cubic inches, solid roller valvetrain, built to turn 8,000 rpm. 614.8 hp @ 8,000 / 467.6 lb-ft. (Lykins Motorsports.)

Small displacement, huge rpm. This is the Cleveland doing the thing it does better than any other Ford small block: the canted-valve head keeps flowing when a Windsor has given up. It is also a purpose-built race engine with a valvetrain budget to match, and nothing about it belongs in a street car.

Reading the ladder

Line the six up and the pattern is clear:

• Under 350 hp means something is wrong — a tired engine, open-chamber 4V heads at 8.6:1, or a cam far too small for the port.
• 380–435 hp is a stock-headed Cleveland with a decent cam. Cheap and reliable.
• 450 hp is the practical ceiling for iron heads, hydraulic flat tappet, pump gas.
• 500–590 hp requires either cubic inches (393, 408) or a serious head, plus a solid or roller valvetrain.
• 600-plus is a race engine.

The jumps between rungs are almost never one part. They are compression, cam, and head working together — which is exactly what the simulator is for. Build each of these six, then change one variable and watch what moves.

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