Self Aligning “Rail” Rocker Arms
Originally the small block engine used a machined slot in the head to guide the rocker arm on the valve. It has been common to enlarge this hole and install a guide plate when switching to a high performance valve train. Later model engines utilize a small alignment slot or “ears” on the valve tip end of the rocker where it contacts the valve. These rockers must be used with long stem valves. These applications can be easily identified by a large (1/2”) hole where the pushrod passes through the head and the fact that there is no pushrod guide plate. If the head in question has either a guide plate or a slot to guide the pushrod, the rail type rocker arms cannot be used.

Conventional Rocker Arms
This type rocker arm was used on 289 hp and 1963-1966 289 engines. The cylinder head had a slot cast in the head where the pushrod passed through. This slot guided the pushrod and aligned the rocker arm with the tip of the valve. Some heads have been modified to use a pushrod guide plate instead of this slot. Since there are no rails on the end of the rocker arm, a shorter tip is used on the valve. This type of rocker arm can be used only in conjunction with either a slot in the head or a guide plate but not both.

Fulcrum Style Rocker Arms
Fulcrum type rocker arms are used on most 351C and 351-400M engines originally equipped with hydraulic cams as well as 429-460 engines made without guide plates. These rocker arms used a fulcrum or “sled” in conjunction with a bolt to secure the rocker arm to the head. Pre- 1977 models used a slotted pedestal cast into the head to keep the rocker arm aligned with the tip of the valve, while later 5.0 351W engines, and many of the modified engines used a stamped steel guideplate under the rocker arm fulcrum to align the rocker arm. To replace rocker arms of this type with the adjustable Magnum or any roller rocker arm, screw-in studs and guide plates will be necessary. These engines can be easily converted by using Part #4504-16 studs which feature a 5/16” thread on the lower portion of the stud. This will screw directly into the holes in the head, and since these engines use a long tip valve, the rail type Magnum (Part #1431-16) adjustable rocker arm can be installed.

”FE” Shaft Rocker Arms
The 332-428 “FE” engines use a shaft rocker arm design. The standard nonadjustable rocker arms will work well with the smaller hydraulic cams, but when installing any solid lifter cam or any hydraulic cam larger than a 292H, the rocker arms must be replaced with adjustable rockers. They can be found on page 274.

Timing Chain Set
When installing a cam in any small block engine, be sure to check items such as the upper and lower cam gears, cam gear spacer, fuel pump eccentric, cam retention plate and front cover clearance. Ford has changed the arrangement of these items through the years and interference and misfits can occur. A Part #3220 timing chain set should be used on pre-1972 221-351W engines. On 1972 and later engines, a Part #3230 chain set should be used. Hydraulic roller equipped 5.0 engines (1985 and later) must use a Part #2138 timing set to ensure proper upper gear fit to the nose of the camshaft.

Camshaft Dowel Pin/Fuel Pump Eccentric
Two different length dowel pins were used in the front of the cams in 221-351W engines. In 1972 and earlier engines, a longer (1.375”) dowel pin was used so that it would extend through the one piece fuel pump eccentric used on these engines. The 1973 and later engines utilized a two piece fuel pump eccentric which required a shorter (1.125”) dowel pin. If no eccentric is used, a thicker than standard retaining washer must be used to make up for the thickness of the eccentric. The cam gear MUST be pulled tightly against the snout of the cam. If the gear is not tight against the step at the front of the cam the bolt will come loose and engine failure is sure to occur.

Dowel pin failure is fairly common in Small Block Ford engines. This is almost never the result of a defective or soft dowel pin. It is most often caused by the bolt in the center of the cam coming loose and allowing the dowel pin to be loaded and shear. The center bolt should always be torqued to the manufacturer’s specification and a suitable thread lock used to prevent the bolt from coming loose.

Valve Stem Oil Seals
When changing to a higher than stock lift camshaft, it is common to have a clearance problem between the bottom of the spring retainer and the top of the valve stem oil seal. Before final assembly of the heads, install one seal, one valve and one retainer without the spring. Measure the distance between the top of the seal and the bottom of the retainer to be sure that it is greater than the lift of the valve by at least .050”-.060”. Be sure to take into account any extra lift due to higher ratio rocker arms.

Flat Tappet Break-In
All higher lift hydraulic and solid flat tappet cams will require special attention during the break-in process. Special springs and certainly tender loving care will be required to ensure long life of the cam. Please refer to the instructions in your cam box for complete procedures. If ever in doubt, please call the COMP Cams® CAM HELP® line at 1-800-999-0853.