The Ford V-8 Engine Workshop
351 Cleveland Family
351C, Boss 351, 351 CJ, 351M, 400

With its free breathing large port canted valve head design and rugged block, the 351 Cleveland was an engine designed to make real horsepower. The 351C was used very successfully in NASCAR and drag racing. The 400 engine has a longer stroke, and higher cylinder deck. The 351M shares this taller block with the 400.

351 Cleveland Family
Bore Stroke
  3.50" 4.00"
4.00" 351 400

The Cleveland family engines are easily identified. The water outlet sits vertically on the top of the block. The distributor leans slightly to the passenger side. The cylinder heads are large, thick in the direction between intake and exhaust flanges. The valve cover mating surface is fairly rectangular, with 8 attaching bolts. The timing chain is contained within a cavity in the block. The cover is a flat plate behind the water pump.

Cleveland Family Cylinder Heads
The Cleveland design cylinder heads are the real trick to the engine's performance. Several versions exist. Monsterous ports are found on the four barrel (4V) variety giving very high flow capacity on an all out race motor. Somewhat smaller ports on the 2V version result in increased low-end torque, perhaps better suited to today's street applications. The combustion chambers were made in closed chamber quench shape, and also in a lower compression open chamber style. Engines designed for hydraulic lifter camshafts use slotted rocker arm pedestals, for non-adjustable rockers. These slots maintain the pushrod alignment. 1971 Boss and 1972 High Output engines featured mecahnical lifter camshafts with flat pedestals for adjustable rocker arms and pushrod guide plates. These heads also have machined valve spring seats for use with mulitple coil valve springs. The high performance heads utilize single groove valve stem locks. Australian heads come in even more variety.

4-barrel heads may be identified by the casting mark at the upper corners of the valve cover mating surface. Australian heads (at least the ones I've seen) and Boss 302 heads do not have these marks. A casting number identifying the head is found on the deck side.

Head Chamber Port
Two barrel
Small 2.05" 1.65" 1970/ 351C-2V, 351M, 400
Four barrel
Large 2.19" 1.71" 1970/71 351C-4V
D0AE-G, -M, -N, -R, D1AE-GA
Boss 351 Closed
Large 2.19" 1.71" 1971 Boss 351
351 CJ Open
Large 2.19" (71/72)
2.05" (73/74)
1.71" (71/72)
1.65" (73/74)
1971 351 CJ
1972/74 351C-4V
351 HO Open
Large 2.19" 1.71" 1972/73 351 HO
Boss 302 Closed
Large 2.23" 1.71" 1969 Boss 302
C9ZE-A, -B
Boss 302 Closed
Large 2.19" 1.71" 1970 Boss 302, D0ZE-A, -B
Service replacement D1ZE-A
Small 2.05" 1.65" 1972/83 Australian 302C-2V
Small 2.05" 1.65" 1972/73 Australian 351C-2V
Small 2.05" 1.65" 1976/83 Australian 351C-2V
Large 2.19" 1.71" 1972/73 Australian 351C-4V

4-bolt Mains While the 4-bolt main caps are found on only some of the 351C-4V engines, all 351C blocks are cast with provisions to accept the caps. The registration saddle is machined the same wide size as the 4-bolt engines. The supporting bulkheads are the same as the 2-bolt blocks, allowing the extra holes to be drilled and tapped.
4-bolt main bearing caps are used to support higher horsepower and continued high speed operation.

These are found on:

R-code Boss 351, 1971
R-code 351 HO, 1972
Q-code 351 CJ, 1971-73

351C vs. 351M
The 351M is sort of a hybrid between a 351C and the 400. The 351C and 351M have the same bore and stroke - 4.00" x 3.50" (also shared by the 351W and the 352). The 351C, 351M, 351W, and all other small blocks share the same bore spacing and cylinder head bolt pattern. Cleveland style heads were first used on the 1969 Boss 302.

The 351M has the higher deck block of the 400. This makes the engine wider and heavier than a 351C. As a result, 351M has longer connecting rods.

The 351M uses the larger 351W / 400 sized crankshaft journals. Stronger in the heavy duty truck sense, but more friction for performance applications at high RPM.

  351C 351M 400 351W
Deck height 9.206" 10.297" 10.297" 9.503"*
Rod length 5.780" 6.580" 6.580" 5.956"
Main journal 2.749" 3.000" 3.000" 3.000"
Rod journal 2.311" 2.311" 2.311" 2.311"
Compression Height 1.647" 1.947" 1.647" 1.769"

* 1969/70 351W deck is 9.480"

The 351C was available with both 2-barrel and 4-barrel heads, with very different port sizes. The 4V size was the choice for high performance builders in the '70s. The 351M is available only with the smaller port, 2V heads. These are more practical on a street engine where low end torque is desired.

The 351C uses the Small Block (289/302) bellhousing bolt pattern. The 351M and 400 use the Big Block (429/460) bellhousing bolt pattern, with the exception of a fairly rare 1973 block.

All 351C blocks can be machined for 4 bolt mains.

The 351M/400 uses thinner wall block so isn't as strong after an overbore, and more prone to overheating.

351M/400 blocks cast at Michigan Casting Center before March 1977 had casting problems, resulting in cracking of the water jacket inside the lifter gallery. Blocks with date codes of 7C01 or later should be OK.

Cleveland family engines use a distributor that will physically interchange with those of the 429/460 big block.