FORD TECH INFORMATION
Ford has produced some of the most powerful engines to ever come
Big Block “FF”, Uses “34” Prefix
out of Detroit. With the V8 engine sizes ranging from 221-460, there is an
The engine commonly referred to as the Ford Big Block is the 429-460
engine size and configuration to cover just about any need or application.
and was used in light trucks and motorhomes. It is an outstanding engine
Ford engines do have some unique characteristics not found in any other
for boats, bracket racing or towing. It typically has a similar but larger
make, so in this section we will try to familiarize you with some of the
“Cleveland” style valve train.
more common differences. This valve train related information should
help you when choosing parts or assembling your engine.
Modular Type Engines
The Ford “Modular Engine” was introduced in the early 1990’s, with the
idea of designing a new generation of engines from scratch, rather than
basing them on then-current production engines. They were developed to
Small Block, Uses “31” and “35” Prefixes
replace all existing Ford V8 pushrod engines. The “Modular” term came
This is the standard engine in most V8 applications. It has been around
about because of the many interchangeable components between the
since the early 1960’s and remains very popular today in many
SOHC and DOHC engines, as well as the ability of Ford to machine and
configurations. The Small Block Ford engine is commonly referred to as
assemble the various engines on the same assembly lines.
the 5.0 engine found in the Mustang for many years. This engine has
The design focuses on low friction, excellent sealing and increased
become one of the most frequently modified engines Ford has ever
block stiffness. With a modern block and head design in 2 valve, 3 valve,
produced. There are a few differences in the valve train of this design, but
and 4 valve configurations, the engines are both versatile and powerful.
for the most part, they are the same. One thing to remember is that the
They have a sophisticated overhead cam design in both single and dual
221-302 engines have a very short deck height, requiring a short
overhead cam versions that utilizes a roller finger follower to reduce
pushrod. The 351W engine, on the other hand, has a tall deck and a
friction, increase rpm potential and eliminate maintenance.
longer pushrod. The 1985-1995 5.0 blocks differ from the earlier blocks
in that the lifter bosses are taller to accommodate the hydraulic roller
All of the cylinder blocks have deep skirts, and nearly all of the main
lifters. The base circles of the cams for these blocks are larger because
caps are cross-bolted. SOHC engines have cast iron blocks; DOHC
of the higher position of the lifters. These engines use either a prefix “31”
engines have aluminum blocks. All cylinder heads are aluminum, with
(302) or a “35” (351) camshaft, depending on the firing order.
very long head bolts to reduce distortion of the cylinder bores and improve
sealing. The new design also allows the accessories to be rigidly mounted
SVO V8 Race Engine, Uses “35” Prefix
directly to the block.
This engine is almost always found in all out racing, and is a cross
between the Windsor and Cleveland designs. It utilizes a Windsor type
4.6L & 5.4L 2 Valve SOHC, Uses “102” Prefix
block and a Cleveland type head. The newest of the head designs is
The 4.6L version of this engine first came out in the 1991 Lincoln Town
referred to as the “Yates” head.
Car and later was installed in the Crown Victoria, Grand Marquis,
Thunderbird and Cougar. This engine has grown to become the popular
Cleveland/Modified, Uses “32” Prefix
5.0 Mustang replacement.
This design was introduced in 1969 and was available as a 351
Cleveland, a 351C Boss or a 351/400 Modified. The easiest way to tell
In 1997 the 5.4L version of the 2 valve SOHC engine was introduced.
these engines from the standard small block is by looking at the front
This engine, known as the "Triton" truck engine, has numerous parts that
covers. The small block / SVO engines have a cast aluminum front cover
are interchangeable with the modular car engines. However, not all are
and water pump housing. The Cleveland/Modified engines have a
identical since the truck engines are built to handle more severe duty.
stamped steel flat front cover. Other than a few rocker arm differences,
the valve train in all of these engines is very similar.
4.6L & 5.4L 3 Valve SOHC, Uses “127” Prefix
The 4.6L SOHC 3 valve engine is available in today’s Mustangs. The
Big Block “FE”, Uses “33” Prefix
engine features variable cam timing, allowing the valves to open and
Ford’s “FE” engine family was introduced in 1958 and was available
close earlier or later as needed for optimum power.
as either a 332 or a 352 version. Later, the range was expanded to
This technology was first introduced in 2004 in the 5.4L 3 valve DOHC
include 390-428 versions. They have been out of production since the
engines. This engine, also known as the "Triton", is primarily in the
mid seventies but remain popular today. These engines utilize a shaft
rocker arm system and can be most easily recognized by the fact that
the intake manifold is very wide and extends part way under the valve
4.6L 4 Valve DOHC, Uses “106” Prefix
covers. Almost all of the parts in the “FE” series are used only in this
This engine showed up first in the 1993 Lincoln Mark VIII and later in
engine and are not interchangeable with other engine families.
the front-wheel drive Continental. It has since been put in performance
cars, such as the Mustang Cobra.
FORD TECH INFORMATION
Whenever you are using a high performance camshaft and have
Firing Order, Small Block & SVO
problems with the valves not staying properly adjusted, one of the first
This is one of the most common questions asked by our Ford
things to check is the rocker arm studs. Most early model small block
customers. The firing order for the early 221-302 engines and the early
heads utilized pressed-in studs. When high spring loads and high engine
5.0 engines is 1-5-4-2-6-3-7-8. This is the firing order for all prefix “31”
speeds are used with these stock type studs, they tend to pull out of the
cams and is the standard replacement cam for all early engines. The later
heads. You can check for this by laying a straight edge across the top of
5.0 engine and all 351 engines are designed to use the 1-3-7-2-6-5-4-8
the studs to see if any of the studs are too high and out of alignment. If
firing order. This is the firing order for all prefix “35” cams, and cams
so, the heads should be removed and machined for screw-in studs.
ordered for these engines should use this prefix. Other than the firing
order, the cams are identical. By changing the spark plug wiring at the
Positive Stop Stud
distributor these cams can be interchanged.
This type stud was used on 1969-76 302 and 351W engines, as well
•••EXCEPT IN MASS AIR VEHICLES •••
as 1968-72 429 engines with hydraulic cams. They do not allow for lifter
adjustment and work only with smaller cams when the dimensions of the
engine (block, head deck height, etc.) remain close to stock. They also
By far, the most common problem encountered when installing a new
don’t work on solid lifter cams.
high performance camshaft is the incompatibility of the existing valve
COMP Cams® offers an adjustment kit (Part #4610-16 on page 276) for
springs to the new cam. All of the factory valve springs are designed to
use with the stock positive stop studs. For high performance applications,
work with a certain lift cam, and since most aftermarket cams have
this type of stud should be replaced with the more conventional screw-in
higher lift, the spring must be addressed. It is highly recommended and a
type, along with the pushrod guide plates.
requirement of the warranty that the suggested springs be installed along
with any COMP Cams® camshaft.
302-351W Ford Small Block
High strength adjusting nut included
Most Ford cylinder heads utilized a step cast into the head that acted
as the valve spring locator. When installing a dual spring, it is highly
recommended that this step be removed by machining to minimize the
possibility of coil binding the inner spring.
Spacer allows adjustment of
Whenever installing a high-tech racing cam in any engine, the cylinder
valve train by raising nut away
heads must be equipped with the correct valve springs, screw-in studs,
from the bolt shoulder
guide plates and hardened pushrods. The increased loads and ultra high
speeds of the racing engines make this a necessity for valve train stability.
The conventional stud is usually found on early model 221-302 engines
and all engines originally equipped with a solid lifter camshaft. This type
of stud uses a locking nut or polylock to keep the valve adjustment
Must be greater
than valve lift
FORD TECH INFORMATION
Self Aligning “Rail” Rocker Arms
Timing Chain Sets
Originally the small block engine used a machined slot in the head to
When installing a cam in any small block engine, be sure to check
guide the rocker arm on the valve. It has been common to enlarge this
items such as the upper and lower cam gears, cam gear spacer, fuel
hole and install a guide plate when switching to a high performance valve
pump eccentric, cam retention plate and front cover clearance. Ford has
train. Later model engines utilize a small alignment slot or “ears” on the
changed the arrangement of these items through the years and
valve tip end of the rocker where it contacts the valve. These rockers must
interference and misfits can occur. A Part #3220 timing chain set should
be used with long stem valves. These applications can be easily identified
be used on pre-1972 221-351W engines. On 1972 and later engines, a
by a large (1/2”) hole where the pushrod passes through the head and the
Part #3230 chain set should be used. Hydraulic roller equipped 5.0
fact that there is no pushrod guide plate. If the head in question has either
engines (1985 and later) must use a Part #2138 timing set to ensure
a guide plate or a slot to guide the pushrod, the rail type rocker arms
proper upper gear fit to the nose of the camshaft.
cannot be used.
Camshaft Dowel Pin/Fuel Pump Eccentric
Conventional Rocker Arms
Two different length dowel pins were used in the front of the cams in
This type rocker arm was used on 289 hp and 1963-1966 289 engines.
221-351W engines. In 1972 and earlier engines, a longer (1.375”) dowel
The cylinder head had a slot cast in the head where the pushrod passed
pin was used so that it would extend through the one piece fuel pump
through. This slot guided the pushrod and aligned the rocker arm with the
eccentric used on these engines. The 1973 and later engines utilized a
tip of the valve. Some heads have been modified to use a pushrod guide
two piece fuel pump eccentric which required a shorter (1.125”) dowel
plate instead of this slot. Since there are no rails on the end of the rocker
pin. If no eccentric is used, a thicker than standard retaining washer must
arm, a shorter tip is used on the valve. This type of rocker arm can be used
be used to make up for the thickness of the eccentric. The cam gear
only in conjunction with either a slot in the head or a guide plate but
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.
Fulcrum Style Rocker Arms
Dowel pin failure is fairly common in Small Block Ford engines. This is
Fulcrum type rocker arms are used on most 351C and 351-400M
almost never the result of a defective or soft dowel pin. It is most often
engines originally equipped with hydraulic cams as well as 429-460
caused by the bolt in the center of the cam coming loose and allowing the
engines made without guide plates. These rocker arms used a fulcrum or
dowel pin to be loaded and shear. The center bolt should always be
“sled” in conjunction with a bolt to secure the rocker arm to the head. Pre-
torqued to the manufacturer’s specification and a suitable thread lock
1977 models used a slotted pedestal cast into the head to keep the rocker
used to prevent the bolt from coming loose.
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
Valve Stem Oil Seals
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
When changing to a higher than stock lift camshaft, it is common to
and guide plates will be necessary. These engines can be easily converted
have a clearance problem between the bottom of the spring retainer and
by using Part #4504-16 studs which feature a 5/16” thread on the lower
the top of the valve stem oil seal. Before final assembly of the heads,
portion of the stud. This will screw directly into the holes in the head, and
install one seal, one valve and one retainer without the spring. Measure
since these engines use a long tip valve, the rail type Magnum (Part
the distance between the top of the seal and the bottom of the retainer to
#1431-16) adjustable rocker arm can be installed.
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.
”FE” Shaft Rocker Arms
Flat Tappet Break-In
The 332-428 “FE” engines use a shaft rocker arm design. The standard
nonadjustable rocker arms will work well with the smaller hydraulic cams,
All higher lift hydraulic and solid flat tappet cams will require special
but when installing any solid lifter cam or any hydraulic cam larger than
attention during the break-in process. Special springs and certainly tender
a 292H, the rocker arms must be replaced with adjustable rockers. They
loving care will be required to ensure long life of the cam. Please refer to
can be found on page 274.
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.
FORD TECH INFORMATION
High Ratio Rocker Arms
A higher than standard ratio rocker arm moves the pushrod closer to
lifter bores. The lifters must not push the guides up as the lifters rise, and
the rocker arm stud. It then becomes necessary to check the clearance
the lifters must not drop below the guide bar as they go all the way down.
between the pushrod and the head where the pushrod passes through the
If either of these conditions exist, the base circle of the camshaft is
head. This is a very common problem and should be checked whenever a
incorrect and must be changed prior to complete installation.
rocker arm ratio change or pushrod diameter change is made.
COMP Cams® has developed new Pro Magnum™ hydraulic roller lifters
Rocker Arm Geometry
that will eliminate the need for the different base circles. This lifter, Part
#8931-16, is a captured link bar style lifter that is a simple drop-in design
Proper rocker arm geometry is necessary to ensure the maximum
for most Small Block Ford applications. We also offer a Big Block Ford
benefit from any cam design. Camshaft base circle, block deck height,
version, Part #8934-16.
cylinder head design and lifter design all contribute to possible errors in
geometry which must be compensated for with pushrod length. Usually a
Camshaft Retention Bolt
longer than stock pushrod will be necessary in a high performance
engine, but care must be taken to choose the correct length. A
Most V8 Ford engines used a 3/8” bolt to secure the upper cam gear
comprehensive explanation of the checking procedure can be found on
to the cam. Almost all racing engines use a 7/16” bolt for this application.
Be sure to check the compatibility of the bolt to the cam, as a 3/8” bolt in
a 7/16” cam will almost certainly result in catastrophic engine failure.
Multi Groove Valves
Most of the COMP Cams® racing roller cams will come with the 7/16” hole
in the cam.
No longer is it necessary to convert to “Chevrolet” style single groove
valves to benefit from the superior strength of COMP Cams® Super Locks™
Camshaft Journal Diameter
and the variety of spring retainers available with this lock. Super Locks™
are now available for the multi groove valves used in most 351C and
Many of the newer all out racing engines utilize a larger than standard
351M-400M applications. They are available in pairs or in sets and can be
cam bearing journal diameter. The advantages of the larger diameter are
found on page 311.
less flex and a larger base circle to smooth out the lobe design, making
this a very desirable addition to any extreme racing engine. The most
Hydraulic Roller Cams
common sizes other than stock are: 2.051” (babbit bearing, all 5 common
size journals), 2.081” (roller bearing, all 5 common size journals) and
In those engines originally equipped with hydraulic roller camshafts,
2.165”/1.968” (roller bearing, commonly referred to as the “Large
conventional flat tappet hydraulic and solid lifter cams can be used. It will
be necessary when making this change to use the corresponding cam,
lifters, pushrods, rocker arms, valve springs and timing chain set.
Any of these sizes should be available, but none are interchangeable.
Make sure to specify journal size when ordering your cam. If no special
Retro-Fit Hydraulic Roller Cams
size is requested, the standard journal size will be chosen.
COMP Cams® has developed a special kit to allow the installation of
hydraulic roller cams in standard Ford V8 engines (289-351W, 351C, 351-
400M) not originally equipped with hydraulic roller cams. This kit uses
many of the same parts as the factory roller cam equipped 5.0 engines
HE TOOL STORE THAT NEVER CLOSES
Powerhouse® offers 800+ professional quality, high performance
use, including the lifter guides and retention tray. This kit can be used only
and hard-to-find tools. From how to books to unique specialty
with specially designed COMP Cams® Retro-Fit Hydraulic Roller
tools, you can order them all online, 24 hours a day, for quick
Camshafts with special base circle size.
shipping straight to your door.
To ensure that you have the correct base circle size: install the cam,
lifters and all lifter retention hardware. Slowly rotate the camshaft, looking
closely at the top of the lifter where it contacts the guide bar. As the lifters
move up and down, the lifter guides should remain flat on the top of the
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