351 Cleveland first upgrades, in the order that works
The Cleveland punishes the wrong order more than most engines, because its heads are big and its factory cam is small. Buy the parts in the sequence below and each one pays for itself; buy them out of order and the first two do nothing until the third one arrives.
1. Springs and a cam, together
Not a cam, then springs later — together. A 2V or a 1970 4V is held to the low 300s by a cam that was designed for emissions, and the head above it can flow for 450. On the Speed Secrets test the cam alone (with springs) was worth 54 hp on a 4V. On a 2V the XE256H or XE262H with its springs is the same move at a smaller scale. This is the single biggest step on the engine and it costs less than a set of heads.
2. A 4-barrel intake and a 600–750 carb
On a 2V this means the Edelbrock Performer 2750 (a 4-barrel flange on 2V ports) and a 600. On a 4V it means an aluminum dual plane and a 750; Holdener's Westech test found no peak-power difference between the RPM Air-Gap and a single plane on a 351, and 37 lb-ft more midrange for the dual plane. Do this after the cam, because the stock cam cannot use the extra air.
3. Long-tube headers
Typically worth 15–30 hp over the factory manifolds on these combinations — the headers page runs the exact number for your build — and worth more with the bigger cam because the exhaust side of a Cleveland head is its weak side. 1-5/8" for a 2V street engine, 1-3/4" for a 4V with the 284H.
4. A dyno tune
Two hours on a dyno is worth 15–20 hp on every combination on this site, and it is the only way to know the timing is where the fuel allows. Every dyno number quoted on these pages was taken with the engine tuned on the dyno first.
5. Compression
Only now. A flat top and a thin gasket on a closed-chamber 4V gets you to 11:1; on an open-chamber head it takes a dome. It is worth real power but it is a teardown, and it changes what fuel you buy for the rest of the engine's life. Most street builds stop at step 4.
Then, and only then: heads or a stroker
Aftermarket heads (CHI 3V, Trick Flow) and a 393/408 crank are the two ways past 450, and neither is a first upgrade. Lykins made 433 hp on factory 4V castings and the factory iron intake; the heads were not what that engine was waiting on.
Put your own engine into the calculator and step through this list one dropdown at a time — the number moves in the order above, and it will show you which step yours is stuck on.
Step through it on your buildSources: Speed Secrets — 351 Cleveland cam test (SuperFlow, STD). Richard Holdener — 351C intake test at Westech (STD). Lykins Motorsports — 1970 351C 4V (Dale Meers Racing Engines, STD).