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Last Updated: 18 Sep 2003
Author: Dave Williams; dlwilliams=aristotle=net
This is one of Mike Cook's Clevelands being prepped for installation in a
DeTomaso Pantera.
Ak Miller racing BOSS 351 blueprint specifications
(from Peterson's Complete Book Of Engines #8, 1972)
Main Bearings ........................... Select fit for .0025-.0030-in.
Crankshaft End-Play ..................... .004-.010-in.
Connecting Rod Bearings ................. Select fit for .0025-.0030-in.
Connecting Rod End-Play (two rods) ...... .018-.022-in.
Piston to Bore .......................... .0065-.0075-in.
Piston to Pin ........................... .006-.008-in.
Piston Pin to Connecting Rod ............ .0006-.0012-in. interference
(pressed pin - minimum 1800
pounds force to move pin)
Valve Stem to Guide, exhaust ............ .0011-.0022-in.
Valve Stem to Guide, intake ............. .0007-.0018-in.
Camshaft Bearing ........................ .001-.006-in.
Camshaft End-Play ....................... .001-.006-in.
Flywheel Hub Face Runout ................ .002-in.
Damper to Crankshaft .................... .000-.002-in interference
Valve Stem Seal to Valve Stem ........... none
(intake and exhaust)
Valve Lash, Intake and Exhaust .......... .026-.028-in. cold (.025-in. hot)
Piston Ring to Groove ................... Compression ring .002-.005-in.
Oil ring snug
Distributor Gear Backlash ............... .007-.017-in.
Distributor Shaft End-Play .............. .004-.025-in.
Piston Ring Gap in Bore ................. .015-.020-in. Compression rings
.015-.069-in. Oil ring
Open and closed chamber heads. All American-market 2V heads were open
chamber. Some Australian 2V heads were closed chamber; many of these have
been imported to the States. Most 4V heads were open chamber, but some were
closed chamber. All BOSS 302 and BOSS 351 heads were closed chamber.
Closed chamber heads make more power than open chamber heads. They raise the
CR, which is usually a good thing, have higher turbulence due to the quench
area, and the smaller chamber makes for a shorter flame path. The open
chamber heads are low on NOx emissions, which is why they are the main type.
All 351M and 400 heads were open chamber.
Here's how Ford's Muscle Parts division recommended you port your BOSS 302 or
351 Cleveland 4V heads. You don't need to make them any bigger, just take
care of some detail work.
How the Cleveland's valves are canted.
Cleveland vs. Windsor valve cooling. Probably just smoke and mirrors from
Ford's marketing department.
From right to left, a standard 4V head, an early '80s NASCAR 4V head with the
ports partially filled with epoxy, and one of the very first A3 aluminum
heads. Ford's aluminum racing heads diverged rapidly from the basic canted-
valve Cleveland design after that.
The M-6049-A3 heads were fairly straightforward aluminum copies of the high-
ported iron 4V heads used in oval track racing. The M-6049-B351 heads were
similar, but with smaller ports. It looks like they just made the whole port
smaller instead of filling in the bottoms to raise the overall port.
The M-6049-C302 was marketed as a variant of the A3, "optimized for engines
under 320 CID", but it's a wholly different head, with rectangular intake
ports and round exhaust ports. The C302 was the beginning of the move from
the Cleveland design to the hybrid Windsor heads that are in current favor.
The exhaust ports of the above heads.
Here's how they recommended you rework the 351C valve for use with the port
work. The valve shape and seat geometry can make up as much as 50% of thr CFM
gained by a porting job.
351 Cleveland rocker types. The "competition" pedestals are a trunnion with a
roller bearing on each side.
Another shot of the roller-pivot rockers. This idea went away for 25 years or
so, then returned via the aftermarket as a modification for 5.0 Windsor
rockers.
This shows the difference between the single and multiple groove valve
keepers. Unless you have a 1971 BOSS 351 or 1972 351 HO you have the multiple
groove keepers. The multigroove design lets the keepers butt against each
other, with enough clearance for the valve to rotate if it wants to. The
single groove design has a gap between the keepers and locks the valve firmly
to the retainer. The multigroove setup was supposed to let the valves rotate
and equalize temperature. It works fine in ordinary applications. It doesn't
work that well in high RPM uses because Ford used compressed Cheez-Wiz to
makes the keepers and they'll fail at high revs. That's not really a concern,
as the 30-year-old two-piece valves will have probably failed about the same
time anyway. Do not even attempt to use the original valves if you're doing a
performance rebuild. It's not even a good idea to re-use them for a stock
rebuild. Throw them away, bite the bullet, and buy new one-piece valves.
It's not cheap, but the alternative is having a head pop off where it's welded
to the stem, and I guarantee that will cost you more than a set of valves.
Back in the early '80s the Ford Motorsport catalog listed these way-cool valve
covers. Yes, they were a combination valve cover and stud girdle! Ford
didn't sell many, probably because prospective buyers figured they'd be more
hassle than they were worth, but the fangle factor is still very high...
A cutaway shot of the stud-covers.
And one more picture... lousy image, but the only one I could find showing the
underside of the valve cover. There's only so much you can do with image
editing software.
Ford Muscle Parts D1ZX-9425-FA intake manifold. This one was slightly
modified by Ak Miller by opening the four separate carb holes to one big hole
for added plenum volume.
Ford Muscle Parts D1ZX-9425-FA single manifold. Ak Miller modified this one
by cutting out the webbing to turn four holes into one for more top-end flow.
Hall Pantera had these Weber intakes cast up with their name on them. Note
how conveniently the Cleveland port spacing matches the Weber bore spacing.
Inglese made these adapter plates to turn one row of carburetors around so the
butterflies mirrored each other on each bank instead of all turning the same
way. This cleaned up some fuel flow differences at low throttle settings.
Assembled Weber setup with stacks. It's as tall as a tunnel ram. In a
Pantera that means a rear view mirror full of stacks. Few Pantera owners with
Webers seem to object, though...
Hall Pantera intake from above. Boss is for mounting carb linkage.
The famed Cross-BOSS intake for the BOSS 302 and Autolite inline four barrel
carburetor. This was designed for works Mustangs competing in SCCA Trans Am
races. Very few were made, but it was a dealer item.
This Cross-BOSS intake has a fabricated cover plate to mount two Autolite
carburetors. Though two 1400 CFM carbs might sound like overkill, the effect
is very similar to an independent runner manifold such as four Webers. Two
1400s were about right for a high RPM 302 or mid-RPM 351; they couldn't feed
the drag racing 351s. Ford later developed a high rise manifold that looked
much like a tunnel ram. It incorporated small plenums beneath the carbs so
they could be shared among the cylinders.
Autolite inline four barrels on true IR intake. That's supposed to be a
Cleveland intake, but it's apparently missing a valley cover and head adapter
piece.
This is a highly-ported Offenhauser Dual Port. This shows a top view that
details the hogging out of the secondary dlenum into one large oval hole, and
it shows the section of the plenum top that was removed to allow porting for
the secondary plenum to deliver the same volume of air to the front two
cylinders as the remaining six. Image: Jim Sams
A view of the plenum note that the secondary plenum path for cylinders 4 & 5
are between the primary bore "tunnels". This area was ported quite a bit.
Image: Jim Sams
The divider milled back about 3/4" at the head flange. This is
said to increase the RPM limit to about 6K for this intake. Image: Jim Sams
Here's the infamous Cleveland oiling system. Despite all the bullshit from
the ragazines it's a perfectly ordinary V8 oiling system - same as the 460,
same as Pontiac, Oldsmobile, and Cadillac V8s, and same as Chevrolet's 2.8 and
4.3 V6s.
Installing oil restrictor plugs. The right one goes to the cam bearing, the
left to the left (driver's side) lifter gallery. The cam bearings are usually
restricted to .062-.068", the lefter gallery to .090-.125", depending on who
makes the plugs.
The 351 Cleveland was available in both two and four bolt versions. All the
blocks were the same; only the caps were different. You could retrofit four
bolt caps to any two bolt block simply by drilling and tapping the holes.
Ford never sold the caps separately, though, so you'd have to get them from a
dead four bolt block.
The Windsor series engines use a separate aluminum timing chain cover bolted
to the front of the block. The Cleveland extends the front of the block
forward and uses a sheet metal cover plate braced by the water pump. The
cast iron extension looks bulky, but it's a thin wall wasting. The Cleveland
is probably only about five pounds heavier there than the Windsor. In
exchange for this, there was one less gasket surface to leak. Windsors had a
habit of oozing coolant into the water pump bolt holes and eating on the
bolts, which would then break off when you tried to remove them. Eliminating
the aluminum cover also reduced problems with galvanic corrosion, which are no
big deal with modern coolants, but were an ongoing problem in the old days.
The first Windsors had aluminum water pumps; the reason they switched to iron
was to reduce corrosion-related warranty claims. They went back to aluminum
when corrosion inhibiting antifreeze became more common.
This is how the coolant flows in the 351 Cleveland. Instead of going from the
heads to the intake manifold like most engines, it goes back through the block
to the cast-iron snout. I don't know of any particular advantage behind this
setup, though the "dry" intake meant you didn't dump a bunch of coolant into
the oil when swapping intakes. I hardly think that was why Ford Engineering
did it, though.
Ford Power Parts (FPP) sold these "Cleveland Capscrew" rods in the mid '80s.
The availability of better rod bolts and inexpensive aftermarket rods has made
this them obsolete, but they were trick in their day.
The capscrews were the same as used on the heavy duty 427 FE rods. FPP
doweled the Cleveland rods to keep the caps in alignment. This is the kind of
cool fangle you keep in mind for 'just in case', like when building stroker
engines.
These headers from Tubular Automotive let you put a Cleveland in a '65-'66
Mustang. Tubular crossed two pipes under the pan to alleviate clearance
problems.
George Klass sells headers to put a Cleveland in Fox Mustangs.
As of 1975 this was the strongest engine Ford's engineers had built when
testing packages for Ford's drag racing program. The Autolite inline four
barrels had some problems carbureting during hard acceleration and kept the
setup from being successful in competition. Notice the small cast aluminum
plenums under the carburetors; even at 2 x 1400 CFM the Autolites were too
small for a high-winding Cleveland when being used on an independent-runner
intake; the plenums let the runners share venturis for more airflow.
2.25" butterflies flowed 1400 CFM per carburetor. Each barrel had its own
metering jets and accelerator pump; essentially separate four one barrel
carburetors in a common body.
The Autolites used Weber-style emulsion tubes. Everything was accessible
without having to remove the carburetor from the manifold.
How many engines got their own carburetors designed for them? Ford sold these
special Autolite 1400 CFM inline four barrels and appropriate manifolding over
the counter to anyone who wanted them.
These adapter plates were available from Advanced Engineering West circa 1985.
They let you mount Fox Mustang serpentine accessories to a BOSS 302.