351 Cleveland History (short)

The 351 Cleveland is not related to the earlier 351 Windsor, except in cubic inches. This designation is important to avoid any form of confusion. The 351C came on the scene with 1970 model introduction topped with either 2V or 4V induction. The most important difference was the heads. Two barrel heads used "open" combustion chambers, whereas 4V heads had smaller "quench" heads to achieve a higher compression ratio. Four barrel heads also had larger valves and ports, and as you might expect, a bit hotter hydraulic cam to handle the extra breathing capability. Both of  these engines were also available in 1971 models, basically unchanged. The BOSS 351 with a solid lifter cam was introduced with the 1971 models. At mid-year (May 1971), the 351C Cobra Jet appeared.

'71 4V/CJ Comparison Summary

The CJ hydraulic cam has more duration and overlap than the 4V. CJ blocks also feature 4-bolt main caps. CJ heads use the "open" 2V combustion chamber design, but retain the larger valves and ports of the 4V head. 4V engines used a model 4300-A Autolite carb with a standard Holley/Autolite manifold bolt pattern. CJ engines, however use a model 4300-D Autolite carb. The "D" model carburetor features small primaries and large secondaries ... and most importantly ... a larger "spread bore " manifold bolt pattern.

'72 4V/CJ Comparison Summary

In 1972, 4V and CJ engines are identical. 1971-72 CJ engines are basically the same, except for a 4-degree retard in cam valve timing specs in 1972

1971 BOSS and 1972 "R" code Comparison Summary

The major difference is in piston and cylinder head design. 1971 BOSS engines use a "quench" combustion chamber, whereas 1972 heads are the "open" type with the 1971-size valves and ports. Both are machined for a mechanical cam valve train, (which is the chief difference between the BOSS and CJ heads that are machined for a hydraulic valve train). '72 engines use a forced flat-top piston (8.8: 1 compression ratio) while the '71 engine uses a forged pop-up piston (*11.1: 1  ratio). The '71 cam provides increased duration and overlays over the 1972 grind.

(* Some automotive literature has reported 11.3: 1 or 11.7: 1 CR)

 

351 CLEVELAND ENGINE COMPARISON

"The Engine of the 1970's"

 

	1971		1972
	4V and CJ	BOSS	4V/CJ	“R” Code
Cylinder Block	4V-2 bolt main caps     CJ-4 bolt main caps	4 bolt main caps selected from hardness	Same as ’71 CJ	Same as ’71 Boss
Cylinder Head	4V-Quench chamber  -64.6-67.6 cc              -non adjustable rocker arm pedestal CJ-Open chamber  -73.9-76.9 cc       -induction hardened exhaust valve seats. Otherwise same as 4V	4V-Quench chamber    -64.6-67.6 cc            Otherwise same as’71 4V,except rocker arm pedestal machined for mechanical camshaft	Same as ’71 CJ	Open chamber 73.9-76.9 cc Otherwise same as ’71 Boss
Cyl. Head Gasket	4V Production composition CJ Reintz Repa comp. For 100 ft-lb torque	Reintz special comp. For 120 ft-lb torque	Same as ’71 CJ	Same as ’71 Boss
Intake Valve	2.19” dia head    11/32” dia solid stem Multi-grove key  Sil-Chrome No. 1	2.19” dia head 11/32” dia solid stem Multi-grove key    Sil-Chrome No. 1	Same as ’71 CJ	Same as ’71 Boss
Exhaust Valve	1.71”dia head     11/32” dia solid stem Multi-grove key   21-4N Steel	1.71”dia head  11/32” dia solid stem Multi-grove key    21-4N Steel	Same as ’71 CJ	Same as ’71 Boss
Rocker Arm Stud	5/16” bolt	7/16” threaded stud	Same as ’71 CJ	Same as ’71 Boss
Rocker Arm Fulcrum	“T” shaped-non adj.	Cylindrical-adjustable	Same as ’71 CJ	Same as ’71 Boss
Rocker Arm	CJ Stamped-high strength 4V production	Stamped high strength	Same as ’71 CJ	Same as ’71 Boss
Connecting Rod	1041-H Forged Steel 3/8” nut and bolt	1041-H Forged Steel -shot peened  and  – magnafluxed -improved durablilty 180,000 psi 3/8” nut and bolt	Same as ’71 CJ	Same as ’71 Boss
Piston	Cast Aluminum-flat top CJ –   9.0:1 CR 4V – 10.7:1 CR	Forged Aluminum Pop up 11.1: 1 CR	Same as '71 CJ Except  9.0: 1 CR	Forged Aluminum-flat top 9.2: 1 CR
Piston Pin	0.912”dia I.D.  non-tapered	0.912” dia I.D.  non-tapered	Same as ’71 CJ	Same as ’71 Boss
Con Rod Bearings	Over-plated copper/lead W/increased eccentricity	Same as CJ	Same as ’71 CJ	Same as ’71 Boss
Oil Pan assembly	Production w/welded windage baffle	Same as CJ	Same as ’71 CJ	Same as ’71 Boss
Oil Level Indicator	Calibrated for 5 quarts	Calibrated for 6 quarts	Same as ’71 CJ	Same as ’71 Boss
Intake  Manifold	Cast Iron-over/under	Cast Aluminum-over/under	Same as ’71 CJ	Same as ’71 Boss
Carburetor	4V-Autolite Model 4300-A w/std bolt pattern CJ-Autolite Model 4300-D w/spread bore pattern	Autolite Model 4300-D  w/spread bore pattern	Same as ’71 CJ	Same as ’71 Boss Except with different calibration
Distributor	4V-Single Point   Dual diaphragm CJ-Dual Point      Dual diaphragm	Same as CJ, except for calibration	Same as ’71 CJ	Same as ’71 Boss
Rocker Arm Covers	Stamped Steel	Cast Aluminum	Same as ’71 CJ	Same as ’71 Boss
Air Cleaner	Ram-air-optional	Ram air	Ram air not available	Ram air not available
Oil    Oil Fill	5 Qt. SAE 10W-30	6 Qt. SAE 40 (summer) 6 Qt. SAE 30 (winter)	Same as ’71 CJ	Same as ’71 Boss
Rear Oil Seal	Rope type	Split lip	Same as ’71 CJ	Same as ’71 Boss
Valve Spring	285 lbs @ 1.32 open	325 lbs @ 1.32 open	Same as ’71 CJ	Same as ’71 Boss
Valve Sp. Retainer	Compatible with multi-groove keeper	Compatible with single-groove keeper	Same as ’71 CJ	Same as ’71 Boss
Valve Spring Key	Multi-groove	Single-groove-hardened	Same as ’71 CJ	Same as ’71 Boss
Valve Stem Seal	Production 351C	Production 429 with shorter skirt for improved lubrication	Same as ’71 CJ	Same as ’71 Boss
Valve Spring Seat	None required	Stamped Steel	Same as ’71 CJ	Same as ’71 Boss
Push Rod	Production	Hardened and ground	Same as ’71 CJ	Same as ’71 Boss
Push Rod Guide Plate	None required	Same as Boss 302	None required	Same as ’71 Boss
Camshaft	Hydraulic 4V-duration 266 degrees i/270 degrees E overlap 34 degrees lift 0.427” CJ-duration 270 degrees i/290 degrees E overlap 46 degrees lift 0.480”/0.488”	Mechanical Duration 29i0 degrees I and E Overlap 58% lift 0.477”	Same as “71 CJ Except valve events retarted 4 degrees	Mechanical Duration 275 degrees I and E Overlap 35 degrees lift 0.491”
Tappets	Hydraulic	Mechanical Internal metering	Same as ’71 CJ	Same as ’71 Boss
Crankshaft	Cast Iron	Cast iron-selected for hardness (90% nodularity)	Same as ’71 CJ	Same as ’71 Boss
Damper	01.10 inertia                    -cast iron hub         -cast iron inertia ring -non-bonded elastic member                     -28.2 oz-in unbalance	0.14 inertia               -nodular iron hub          -wider cast iron inertia ring -bonded elastic member -27.3 oz-in unbalance	Same as ’71 CJ	Same as ’71 Boss
Flywheel	Cast Iron-28.2 oz-in unbalance	Nodular Iron-27.3 oz-in unbalance	Same as ’71 CJ	Same as ’71 Boss

*info from Ford - February 1972

 

 

Some basics of Cleveland building (in no particular order)
by Dan Jones:

- Use single piece stainless steel valves with single groove keepers. Valve
train failure is the number one failure mode for a Cleveland. The stock
valves are two piece with loose fitting multi-groove keepers. If they don't
slip out of the keeper, they'll pop the head off.

- Keep the overbore to a minumum and don't exceed 0.030" without sonic checking.

- Don't use the rubber intake manifold gasket end seals. Buy or make your
own from cork. I peen the block rails with a punch so the gasket won't
squeeze out while you're torquing it down. This also works well on valve
cover gaskets. Use Permatex 300 or a contact cement. Don't use RTV except
in the corners of the end rails and even there I prefer using the red/brown
Permatex. Retain the turkey pan unless the carb heat ports are blocked.

- If you retain the stock rocker arms, make sure you use the steel 4V sled
fulcrums. The 2V fulcrums are aluminum and come apart under load. Also,
there are two types of stock rocker arms (lugged and unlugged) and one of
them (I forget which) has pushrod to rocker arm clearance problems with
high lift cams. Given the high lift of the typical Cleveland performance
cam, roller rocker arms are a good investment for increased valve guide
life. You may have some clearance issues with roller rockers and the valve
covers. If your valve covers are equipped with drip rails (as Boss/HO cast
aluminum and some factory steel valve covers were), you will have to remove
them or bend them out of the way. You may also have to clearance the rockers
arms near the oil filler and PCV baffles. Use the real FoMoCo rubber valve
cover grommets. The repos just don't seam to fit right. Fel-Pro makes a
thick three layer (cork-metal-cork) valve cover gasket that can make the
difference with clearance problems. Permatex the gaskets to the valve covers
and run them dry on the head side if you plan on frequent removals. It is
possible to run adjustable valvetrain, roller rockers and a stud girdle under
a Boss aluminum valve cover.

- Drive a second shear pin in the distributor gear or replace with a hardened
pin. If a little debris (see valve seals below) gets in the pump gears, it
can shear or bend the pin. This retards the timing which leads to sluggish
performance and overheating.

- Don't use umbrella valve seals. Use PC-type teflon seals. The umbrella
ones disinegrate over time and fall into the pan where the get sucked up
by the oil pump.

- The usual Ford oil filter has a bypass valve bult into the filter which
can allow unfiltered oil to bypass the filter. The bypass can also fail,
causing a loss of oil pressure. Consider using Purolator oil filter
number L30119. It's a full size replacement for the FL-1A Ford/PH8A Fram
filter. It has no bypass spring in the middle but it does have the rubber
flapper for anti-drainback. The original application is for a 1978 Nissan
510, 2.0L 4 cyl engine (L20B) which had the bypass valve in the engine
block. This filter cross-references to a Fram PH2850, a Motorcraft FL-181,
and a Wix 51452. However, those filters have not been verified and may
still have the bypass. It appears after 1978, Nissan went to a half height
filter. Purolator part number L22167 fits that application and does not
have the bypass spring but does have the rubber flapper for anti-drainback.

- The stock rods are good to 7000+ rpm with prep. At a minimum, use good (ARP)
rod bolts. Beam polishing and shot-peening are also good but optional.
- Run a PCV valve

- Use a Cleveland specific thermostat. They have a shoulder which is sized
to match the brass restrictor ring in the block (make sure it's there) which
other thermostats do not have. Using a Windsor thermostat (which the parts
counter monkeys will give you half the time) will lead to overheating because
coolant will bypass the radiator. Don't run an excessively cool thermostat.
It won't make a difference in steady state temperature but will slow warm-up
time. I recommend the Robert Shaw 351C thermostat. It's quick acting and
has bleed provisions.

- 4 bolt mains are a nice-to-have but not necessary.

- If the car is set up to handle, use a baffled, oversize, oil pan. A stock
Pantera with slicks can pull over 1.0 g's lateral and the oil in a stock
pan will climb the side of the pan starving the bearings for oil. I know
two Pantera engines that were ruined that way.

- The MPG "Stinger" exhaust port plates may be worthwhile for 4V heads if the
header doesn't turn down sharply at the port exit. The intakes port plates
may be more of a sealing and port match hassle than they are worth. Roush
and Marino Perna at Panteras East make intake port stuffers that go inside
the intake port. A thin layer of epoxy is used to bond the stuffer to the
pot and set screws are used to hold it in place.

- Quench heads (2V Aussie or early 4V) are the best for performance. They
allow higher compression and make more power. Quench heads have a flat
area opposite the spark plug and an open area around the plug. As the
flat top piston rushes up toward the head, the area under the flat reduces
quicker than the area under the open part of the head. The result is the
mixture is forced at towards the plug. The resulting turbulence evens out
temperature and more completely burns the mixture. More power, better fuel
economy, and higher compression on the same octane.

- For street applications, flat top pistons (TRW forged or KB hypereutectic)
are generally used with the quench chambers for a compression ratio in the
10.5:1 range. Pay attention to the manufacturer's ring gap information you
plan to use nitrous.

- Quench heads run best with less spark advance (32-34 degrees) than open
chamber heads. The flame front has a longer distance to travel with open
chamber heads so they require more total advance, maybe 4 degrees or more
than a closed chamber head. A multi-strike ignition, like an MSD-6 series,
will allow an open chamber head to make peak power with less total advance.

- With an open plenum intake and some cam, I like the multi-strike ignitions
like the MSD-6AL (the -AL version comes with built-in rev limiter). They
improve cold start and low rpm performance. You can use any distributor to
trigger.

- Use a quality double row true roller timing chain set (Cloyes, SVO, or similar).
Degree in the cam and mark true TDC on the balancer. Stay away from gimmick
dampers (TCI Rattler, Fluidamper, etc.). Stick with a stock or quality rubber
elastomer type balancer (SVO/ATI, ROMAC). Paint a stripe on for a positive
indication of balancer slip.

- If you need new cam bearings, cut grooves on an old Cleveland cam to use as a
scraper or have a machine shop hone to fit. Cleveland cam bearings were honed
in the block by the factory and new ones are usually too tight.

- For high rpm work with a solid lifter cam, consider the standard oiling mods
(galley restrictors and/or sleeved lifter bushings). For under 6500 rpm
with a hydraulic cam, stock displacement oil pump with a higher pressure
relief spring (or shimmed) is okay. High volume pumps increase output at
lower rpm where it's not needed, unnecessarily loading the cam and distributor
gears and wasting power. Use the SVO or FPP heavy duty oil pump driveshaft.
MPG Head Service (a.k.a. Cam Research) makes a windage tray to fit the stock
pan. The 351M/400 can type pickup can be used to replace the 351C pickup.
Make sure the pickup and the hole in the mating surface align.

- Check the cam and distributor gears for proper contact pattern. You may have
to adjust the position of the gear on the distributor. Also, it's worthwhile
to pull the distributor after a few hundred miles to check the wear pattern.
There have been a rash of cam gear problems that may be due to improperly
machined cam cores.

- Treat 2V and 4V engines as completely different when it comes to picking
components like cams, heads, and intakes. The primary difference between
2V and 4V heads lie in the ports.

- 4V heads have very large ports. The intake, though overly large for most
applications, is shaped decently enough. The exhaust is compromised to
clear the shock towers of early Mustangs and Cougars. The 4V exhaust
port has a hump then a sharp drop with an exaggerated area change. The
port exit area is very large but much of it is wasted and the flow
velocity low. The resulting poor intake to exhaust flow ratio requires
a cam with additional duration (typically 10 degrees or more) and lift on
the exhaust side for best results. 4V heads work best with a dual pattern
cam. Something on the order of 10 to 20 degrees additional exhaust duration
and/or 0.010" to 0.020" additional exhaust lift. 4V heads also like a lot
of lift and keep flowing more air past 0.600" valve lift. The 4V exhaust
port is sized for a 1 7/8" primary diameter header.

- The best horsepower intake for the 4V heads is the Holley Strip Dominator.
It's a single plane and gives up some low end torque but it's still
smooth and tractable. The Strip Dominator is currently out of production
but can be found at swap meets and on the 'net for $325 to $350. A close
second is the Blue Thunder high rise dual plane. It gives up a bit of top
end but has a better low end and cold weather start up. These go for
around $325 new and are available from the usual Pantera vendors. Both of
those intakes are quite tall. If hood clearance is an issue, then you're
best choices are a stock Ford intake or an Edelbrock Performer 4V (a.k.a.
F-351 4V). The Ford 4V intake were produced in iron or aluminum in square
or spreadbore (Motorcraft, not Qjet or Thermoquad) versions. The Offy Dual
Port is probably the best fuel economy, towing, intake for the 4V heads.

- The 2V is a whole different cylinder head, not just a 4V with smaller
ports. The oval ports are smaller, though still decently sized. The
intake ports are biased to the side to get a straighter shot at the valve.
The exhaust port is raised (relative to a 4V), has a moderate area change,
and a nice shortside radius. Though much smaller in cross-sectional exit
area (though not necessarily a smaller minimum area), the 2V exhaust port
flows as much as a 4V, with substantially higher velocities. The 2V exhaust
port is sized for a 1 3/4" primary diameter header which is more than
adequate for 400+ hp. You can use 1 7/8" diameter 4V headers on a 2V port
but you'll loose some of the scavenging effectiveness. Since the heads have
a good intake to exhaust flow ratio, they don't require an exaggerated dual
pattern cam like the 4V and work well with a single (or slightly dual)
pattern cam. Unported 2V heads tend to build flow early (have good low lift
flow) and level off after 0.530" lift or so.

- No high rise dual plane intakes exst for the 2V heads. However, the single
plane Weiand Xcelerator 2V (p/n 7516) is a good high performance intake that
works smoothly at low rpm. The Weiand's intake has ports that are larger
than those of the head. It's essentially pre-ported and requires the heads
be match ported to the intake. For a heavier vehicle, you might want to
try the Edelbrock Performer 2V (a.k.a F-351 2V). It's a low rise dual
plane with that ports match the size of the head ports. Holley made a Street
Dominator (p/n 300-12) open plenum single plane intake for the 2V heads but
it was an economy type manifold it ports smaller than the 2V head and a small
plenum. An Offenhauser Dual Port would probably be better for fuel economy
and low end.

Dan Jones

 

http://www.mustangandfords.com/techarticles/30220/

 

http://www.jason.fletcher.net/tech/flowdata/cleveland.htm

 

http://www.mustangmonthly.com/howto/26378/index.html