351C Performance With Common Parts

351C Performance With Common Parts
A Cleveland Course of Action
A&S Motorsport Builds on 351C Performance with Common Parts
writer: Jim Smart photographer: Mark Houlahan
Ford's 351 Cleveland is legendary for the performance it has given us for 36 years. However, we admit to
being confused by Ford's decision to manufacture the 351C . It already had the 351W, a raised-deck
289/302-based mill conceived to go after Chevrolet's 327 and 350ci small-blocks. The 351C was loosely
based on the 289/302, with identical cylinder spacing, but it had a different oiling system and an Oldsmobilelike front timing cover, main bearing caps, and fuel pump configuration.
Although we have never been able to confirm this theory with Ford insiders, we're convinced Semon E.
"Bunkie" Knudson had everything to do with the 351C's conception. Knudson was hired away from General
Motors by Henry Ford II to run Ford Motor Company during the late '60s. When Knudson arrived in 1967, the
351W was already well underway and scheduled for production beginning in 1969. The 351C was introduced
in 1970.
We base our Knudson 351C theory on design elements that it shares with notable GM V-8 engines. The same
can be said for the 385-series Ford big-block (429/460 ci), which has design elements also borrowed from GM
just about the time Knudson was running Ford. The Cleveland's oiling system, timing cover, and cylinder
heads distinguish it from traditional Ford V-8s. The 351C's canted-valve (poly-angle) cylinder heads are
obviously borrowed from big-block Chevys. Its oiling system, timing cover, and fuel pump configuration are
clearly influenced by Oldsmobile-with the exception of the fuel pump's location on the opposite side. It is the
only Ford V-8 ever produced with a 12/6-o'clock fuel pump bolt pattern like Oldsmobile's.
We will never know for sure, but you can bet Knudson's engineering people walked into Ford and speculated
about what could be done with those stifling small-block Ford heads. The result would be the canted-valve,
large-port Cleveland/Boss 302 cylinder head. What's more, they probably did the same thing with Ford's
LeMans-winning FE-series big-block-replacing it with the 385-series 429/460 big-block later on. We will go out
on a limb by saying each of these engine families survived, because it was undoubtedly a political battle
between Knudson's GM outsiders and Ford's established engineering people.
When Ford introduced the 351C in 1970, it was embraced by enthusiasts for its large-port, poly-angle valve
heads and its ability to produce lots of power. The aftermarket promptly went after performance buffs, setting
them up with single- and dual-plane high-rise manifolds, tunnel rams, ignitions, hot cams, carburetors, and
more. Big-time drag racers took the 351C and put it to work in 8-second Ford compacts, such as the Gapp &
Roush "Tijuana Taxi" Maverick sedan. Saturday-night warriors did the same thing with Mustangs, Fairlanes,
Torinos, and Cyclones, going after the competition with Ford's newest V-8. The 351C wound up being a
phenomenal success during the '70s.
What helped the 351C also contributed to its demise in 1974. When Knudson was fired from Ford in 1970 and
replaced by Lee Iacocca, we're convinced most support for the 351C went with him down the elevator to
Michigan and Southfield. Of course, Ford didn't give up the 351C completely. It raised its deck to create the
400M for 1972, which replaced the FE-series 390/428ci big-block in passenger cars. In 1975, the 351C was
dropped and replaced with a destroked 400M known as the 351M-both had big-block bellhousing bolt
patterns.
We would like to hear your thoughts about the Knudson/351C connection. Can anyone answer us about the
351C's origins? We invite your feedback at [email protected].
Getting 351C Performance
Ford's 351C is challenging because its cylinder heads were never practical for street use. This is a highrevving V-8 designed to do its best work on the racetrack, thanks to big-port heads, poly-angle valves, and
wedge chambers. What makes it successful on the racetrack is what makes it a dog for street use because we
need good low-end torque for the commute. Anyone building a Boss 302 understands this because Boss 302
engines were fitted with modified Cleveland heads. It was designed for high-revving Trans-Am racing, not
fetching groceries. The same can be said for the 351C.
To meet the need for low-end torque, Ford's North American engineers opted for smaller intake and exhaust
ports on the 351C-2V head along with open chambers to get compression down. The downside to this open
chamber is its detonation tendencies. It tends to create two opposing flame fronts under moderate to heavy
acceleration. The very thing it was intended not to do-ping-it does with great regularity. Smaller wedge
chambers actually ping less than open chambers thanks to shape and quench area.
In Australia, Ford engineers improved the U.S. 351 Cleveland head with small 2V ports and tight 4V wedge
chambers. Aussie Cleveland heads are the hot ticket for Cleveland’s with generous build budgets and access
to these heads from Down Under.
The 351 Cleveland has never been easy to build because the best parts are elusive. Because Ford produced
this engine for just four short years, it has become harder and harder to find parts in recent years. What's
more, Cleveland castings have long been plagued with failure issues (cracking). Some can be repaired, but a
lot of them cannot.
We can dream of Aussie heads, which are expensive and hard to find. And we may also consider aftermarket
aluminum heads for the Cleveland, but those don't come cheaply, either. So, lets go with what you can
expect to find at a swap meet or in the classifieds for your 351C build. Our good friend John Douglas in
Riverview, Florida, builds a lot of 351C engines annually. He knows how to build a streetable 351C that you
can live with daily and make lots of power with on a Saturday night.
The 351C block offers unprecedented strength in two- and four-bolt main versions. Through many 351C
buildups, we have learned that all versions of this block are virtually the same except for two- or four-bolt
main caps. All two-bolt main blocks can be drilled and tapped for four-bolt main caps. Strength comes from
heavy main webs wrapped around 2.749-inch main bearing journals. Ironically, the 351C has a smaller main
bearing journal than the 351W, which is larger at 3.000 inches. Smaller mains yield less friction, which is
likely the motivation behind the smaller main bearing size on the 351C.
Cleveland oiling systems from the factory fall short in terms of oil delivery to the main bearings, which bites a
lot of us who build Cleveland’s. It's a good idea to begin Cleveland oiling system mods at the pump. Opt for a
Speed-Pro high-volume pump, which yields 25 percent more volume thanks to a wider G-rotor package and
cavity. It is also advisable to install a 100-psi pressure-relief spring if you're going racing. Ideally, you will
blueprint your 351C oil pump before installation. MCE Engines in Los Angeles, California, can blueprint a
Cleveland oil pump for you and ship it ready-to-install. The next oiling system mod is a restrictor kit from
Moroso (PN 2205), which improves oil flow to the main bearings.
The good news with Cleveland engines is that they're hardy blocks that need a little help if you intend to go
racing. For street use, they need minor modification. As we have learned from other engine builds, oil
passages need to be worked smooth to reduce oil turbulence. The same is true for oil drainback holes, which
need help to improve oil scavenging.
We suggest having any Cleveland block checked for cracks and thin cylinder walls before proceeding with
machine work. Sonic checking cylinder walls helps find weaknesses before machine work. Magnafluxing the
block and crank is also necessary prior to getting started. Work out stress risers and other rough spots to
prevent weaknesses and failure. You can use a die grinder on any block to eliminate weaknesses. The
objective here is to reduce or eliminate any chance of failure. Coating inside surfaces with GE's Glyptol,
available from The Eastwood Company, improves oil-return flow and keeps stray iron particles where they
belong.
Cleveland Vs. Windsor-What's In A Name?
How did 351ci engines get their names? When Ford came out with a second 351ci V-8 in 1970, Ford dealer
technicians found themselves faced with a lot of confusion when it came to engine identification. It is virtually
impossible to confuse the 351W with a 351C because they have completely different cylinder head and block
architecture. In 1970, both were still so new that Ford needed to explain the differences and give each engine
a family name. Ford's solution was to name each engine for the plant from which it was produced.
Raised-deck 351ci engines were named "Windsor" for their Canadian plant across the river from Detroit. Polyangle-valve 351ci engines with wide valve covers were named "Cleveland" for their northeast Ohio roots.
These names stuck and have been used ever since. Some confusion abounds with Cleveland and Windsor
because 221/255/260/289/302ci engines were also produced at the Cleveland Engine Plant. Their castings
were produced at the Cleveland foundry. Added confusion abounds when we find 289/302 heads produced at
the Windsor foundry. The rule of thumb is 221/255/260/289/302ci engines were Cleveland based, with all of
them produced in Cleveland. The 351W engine was Windsor produced. By the same token, the 351C was
Cleveland produced exclusively.
Whenever we call 221/260/289/302ci engines Windsor small-blocks, we're mistaken. None were ever
produced in Windsor. Only the 351W was produced in Windsor, Ontario-along with a smattering of 289/302
small-block heads.
Heads
Cleveland heads were produced in several variations. Most common is the two-barrel (2V) casting with 7477cc open chambers, 2.050-inch intake, and 1.659-inch exhaust valves. These are easily identified by their
open "bowl" chambers and D0AE-E or DOAE-J casting numbers. This is a good street head because the port
size is more conducive to the low- to midrange torque we want on the street. Aftermarket intake manifold
availability is better with these heads as well. The 2V head was used not only on the '70-'74 351C, but the
351M and 400M engines as well, which explains availability.
Four basic types of 351C-4V heads were produced-closed chamber, open chamber, Boss 351, and High
Output. Much of it has to do with compression ratio and mechanical lifter use.
Early 351C-4V engines were fitted with closed-chamber (61-64cc), large-port heads. This is an excellent highrevving street/strip head for those who want iron heads. In 1973-'74, Ford went with a 73-78cc open
chamber in the 4V head, virtually identical to the 2V head. This head is easily identified by its large ports and
2V-style open chambers. It's the least desirable head available, but sometimes it's all you're going to find.
The '71 Boss 351 head is extremely hard to find, thanks to adjustable stud-mounted rocker arms and closed
64-67cc wedge chambers. The '72 High Output that came a year later has adjustable stud-mounted rockers
like the Boss 351. But larger 73-76cc open chambers make it less desirable than the Boss 351 head. The
truth is, aside from the stud-mounted rocker arms and large ports, the '72 High Output head isn't desirable
outside of a restoration.
Block architecture closely resembles Oldsmobile V-8s of the period, with the timing set completely wrapped in
iron with a steel front cover, an iron water pump, and a 12/6 o'clock fuel pump bolt pattern. Do you see the
Oldsmobile connection?
351 Cleveland Performance Engine Build Installing Pistons
Like the Oldsmobile Rocket V-8s of the era, Ford's 351C, 351M, and 400M have wide main caps fore and aft,
with a similar oil pan design. Where the Cleveland differs from Olds is a front sump design. Olds has a rear
sump
John prefers Speed-Pro forged aluminum pistons with coated skirts for reduced friction and improved
reliability. Here, he rolls on rings and readies slugs for installation. John coats the skirts with assembly lube,
and applies a thin film of 30-weight engine oil to the cylinder walls.
The 351C block offers excellent bottom-end support and can take high revs without breaking a sweat. This
makes it stronger than a 351W block. The downside is an oiling system that's inadequate, as it comes from
the factory. Cam bearings and lifters get oil before the mains, which causes oil starvation issues under
extreme conditions. Experienced Cleveland builders opt for all kinds of oiling system mods, including an
external oil line from the front of the block to the rear to improve oil flow at the mains. A restrictor kit is also
available from Moroso
Ford D0AE Cleveland rods are good for up to 400 hp if shot-peened and fitted with ARP bolts. All 351C builds
must be dynamic balanced to prevent vibration and free up power.
Main bearings in the 351C are smaller than the 351W. The logic is less friction. Oil comes from a common
galley that feeds the cam and lifters. We improve oil flow to the mains by controlling flow to the cam and
lifters.
Cleveland’s are clearly different from their 289/302/351W counterparts due to canted-valve cylinder heads.
Canted or poly-angle valves change the location of piston valve relief’s entirely, which makes these pistons
compatible only with Cleveland cylinder heads. Note valve relief positioning at 8 and 2 o'clock, as well as
cylinder notching for additional valve clearance.
Side by side, 351C high- and low-compression chambers are easy to spot. On the left is the open 73-77cc
chamber (low compression). On the right is the 61-67cc wedge chamber (high compression). The most basic
choice facing 351C builders is chamber and port size. Strictly street engines may opt for open chambers and
small 2V ports for good low-end torque. Street/strip engines may go with open or closed chambers depending
on the compression desired. Large ports may impress people, but they do their best work at high rpm. They
offer limited torque on the street unless you plan on leaving the light at 7,500 rpm.
This is the 73-77cc open chamber (low compression) found on all 2V heads, all 1972-74 4V heads, and the
High Output head. Although this chamber is larger, with reduced compression, it is not a desirable one. By
design, it aggravates detonation by creating opposing flame fronts under hard acceleration-hence the pinging.
This is the chamber to avoid if at all possible. You are limited to 4V heads with huge ports if you want wedge
chambers. The Australians got it right by combining conservative two-barrel ports with smaller wedge
chambers.
Here's the more desirable 61-67cc wedge chamber (high compression) used with the 4V and Boss 351 head
casting. The Aussie head uses this chamber with smaller 2V ports for best results.
All Cleveland foundry castings have this logo. Because all 351C, 351M, and 400M castings were produced in
Cleveland, you won't see a "WF" logo (Windsor Foundry).
Cleveland’s and Midlands have different cooling passages between the block and heads from what we find
with 289/302/351W engines. Because the 351C, 351M, and 400M have dry intake manifolds, coolant flows
across the engine via cooling passages like this one between the heads and block. When we bolt Cleveland
heads on a Windsor block, this passage is eliminated, with a new cooling passage drilled to accommodate
289/302/351W intake manifolds.
Externally, 351C-4V heads are identified by this "4" in each corner.
Screw-in adjustable rocker stud pedestals look like this. This is also what you can expect to see with Boss 351
and High Output heads with adjustable rockers and mechanical tappet camshafts.
Hydraulic lifter 351C engines have this bolt/fulcrum rocker-arm fulcrum designed for a no-adjust rocker arm.
Small-block Fords (302 and 351W) from 1977-up have the bolt/fulcrum, no-adjust rocker arm.
John Douglas' porting regiment includes taking stress risers and bumps out of chambers and ports. Stress
risers in combustion chambers create hot spots that can cause detonation problems. This is especially
important in open chambers notorious for detonation issues. John works the bowls and valve seats to smooth
airflow. It looks like John has gone with a standard three-angle valve job here for the street. A five-angle
valve job costs more, but it produces even more airflow
John specifies Fel-Pro in his engine builds. We recommend Fel-Pro Print-O-Seal head and intake manifold
gaskets for exceptional sealing. This isn't a biased opinion based on advertising dollars-it's based on years of
experience with Fel-Pro gaskets and dozens of different engine builders who insist on them.
Cylinder head installation and torque values may not seem like a big deal, but they are. We've even had
builders suggest no sealer on cylinder-head gaskets and even cleaning the factory clear coat off head-gasket
fire rings with carburetor or lacquer thinner. This allows for better heat dissipation and cylinder sealing
because high revs actually lift cylinder heads off the block. Having a clean, undisturbed fire ring is critical
during installation. Use Latex gloves to keep skin oil off your gaskets. Proper head gasket installation is
confirmed by looking for the gasket in the lower left hand corner of this image. If they're installed properly,
you will see the gasket.
Heads are torqued inboard to outboard in one-third values. Total torque for 351C heads is 110 ft-lb. Divide
that into thirds, or 37 ft-lb of torque per sequence.
Crane has provided John with a 52HR00026 hydraulic roller camshaft. This is an aggressive 52-HR-232/3522S-10 roller cam with 110-degree lobe separation, 0.609/0.621-inch valve lift, and 294/298 degrees duration.
This yields a civilized idle and comes on strong at high revs.
John suggests plenty of assembly lube on pushrod tips, roller tappets, and rocker arms. These are Crane
hydraulic roller tappets (PN 36432-16) for the 351C that are linked together instead of retained with a spider
and dog bones. Although this is more expensive, it's a better system that requires no block retrofit work. John
suggests soaking these guys in engine oil overnight for complete lubrication saturation.
These are Crane Energizer 1.7:1 forged aluminum rocker arms designed for the 351C, 351M, and 400M. They
sport a precision needle bearing fulcrum and roller tip to reduce friction. John stresses checking rocker armto-valve stem geometry, which is rooted in pushrod length. When it comes to adjustment, have both valves
at rest on compression stroke, and then slowly tighten the poly-lock until the pushrod cannot be turned. Then
tighten 1/2-3/4 turn for street.
We cannot stress enough the importance of oil-pump clearances. Oil pumps do not always clear crankshaft
counterweights, and sometimes the pump housing must be ground to clear the crank. Check all clearances
and make your minimum 0.060 inch
John suggests always checking oil pick-up dimensions before anchoring the pan. An oil pick-up pressed
against the pan sump can chafe and create metal shavings for the oil pump to ingest.
Cleveland engines need serious cooling capacity-the help you get from a high-flow water pump. We suggest
cleaning rough surfaces that can create fluid turbulence and hot spots.
All 351C, 351M, and 400M engines have this coolant flow restrictor just below the thermostat as shown. Do
not remove this restrictor.
Oil-pan installations seem like such a simple task, but if you want to prevent leaks, pay close
attention to what you are doing. John likes 3M's yellow Gasket Adhesive, and uses it sparingly on
the rails only. At the end gaskets, he uses The Right Stuff; a silicone adhesive in a pump can-again,
sparingly. Pan bolts are snugged, but not over-torqued. Overtorque these and you distort the pan.
It doesn't take much torque to snug the gaskets adequately.
John uses a thin film of The Right Stuff at the intake ports to reduce chances of an internal vacuum leak.
Along the block rails, he rolls down a bead of RTV or The Right Stuff. You don't need much here. As it cures, it
expands.
John has chosen Holley's 4150 750-cfm carburetor atop a Weiand X-celerator single-plane manifold. As you were
taught in Engine Basics 101, a single-plane manifold makes all kinds of high-end horsepower, but it is not an allaround street manifold. John also chose a Plenum Divider Kit (PN 128351) for this manifold. Torque isn't stellar
under 4,000 rpm, but above 4,000, get out of the way-374.7 lb-ft at 5,300 rpm, with 408.8 hp at 5,900 rpm. Not a
broad powerband, but plenty at full throttle above four grand on the dyno.