How we calibrate the 351 Cleveland simulator
Every tool on the MMM network is held to the same rule: it has to land within a few horsepower of real, published dyno pulls, or it gets changed. We keep a list of anchor tests — engine, parts, dyno, correction factor, peak numbers — and drive the calculator through each one. When it misses, the model changes, not the anchor.
The current 351 Cleveland anchors
| Richard Holdener — Boss 351 replica | Westech, STD. 11.0:1, factory 4V closed-chamber iron, factory 4V intake, Boss solid grind, Holley 750, long tubes. 383 hp / 391 lb-ft. |
|---|---|
| Speed Secrets — cam test | SuperFlow, STD. Stock-head 4V, Performer RPM. Boss cam 397 / 401 → COMP XE284H 451 / 411. |
| Richard Holdener — intake test | Westech, STD. 4V with XE284H: RPM Air-Gap 450.4 / 411; Funnelweb single-plane 450.4 / 373. |
| Lykins Motorsports — 1970 351C 4V | Dale Meers Racing Engines, STD (29.92"/60°F). Stock 4V heads, stock iron intake, mild hydraulic roller, pump gas, under 10:1. 433.5 / 427.7. |
| Lykins Motorsports — 354ci race engine | SuperFlow, STD. Iron 4V race port, solid roller 259/267, race fuel. 614.8 @ 8,000 / 467.6. |
| Competition Engines — 408 stroker | SuperFlow, STP/STD. Tongued iron 4V, solid flat tappet, Pro Systems 780, pump gas. 588.5 / 536.4. |
STD, SAE, and why Westech numbers look high
Numbers on this site are engine-dyno, flywheel, STD-corrected unless the page says otherwise. STD (SAE J607) corrects to 29.92" and 60°F dry air; it is the standard Westech and most engine shops print, and it reads about 3–4% higher than SAE J1349 on the same pull. If a magazine number looks bigger than yours, check the correction line on the sheet before you check the engine.
If you are comparing to a chassis dyno, expect 15–20% less at the tire on a manual, more with an automatic. Motorcycle tools on the MMM network read rear-wheel because that is how every published Harley number is taken; the V8 tools read flywheel because that is how every published V8 number is taken.
What "HP at the limit" means
When the calculator prints "HP at the limit" instead of "Peak HP," the springs, lifters, or ignition you picked stopped the pull before the cam ran out. The number is real for that parts list — it is what the engine makes at the rpm the valvetrain allows — but it is not what the cam could make with a spring that matched it. Every one of the anchor engines above was tested with springs matched to the grind.