Reply to "Cylinder head identification."

> Hope all is well. The casting number indicates the heads are the "B351" heads.

Yes, those are B351's. The high port canted valve aluminum heads included
three basic designs: the A3, B351, and C302. The A3 was the earliest
of this family of heads. They were basically an aluminum evolution of
the Pro Stock high ported iron 4V's. Back in the '70's, when 351C's
were campaigned in the Pro Stock drag class, it was standard practive
to cut off the exhaust ports of iron 4V Boss 351 heads and bolt on an
aluminum plate that had a raised exhaust port location. Some racers also
filled in the bottom 1/3 or so of the intake port with epoxy or aluminum
port stuffers. The A3 is basically an improved aluminum version of a
Pro Stock high ported 4V head. The intake port is the same width as
an iron 4V (and is in the same location) but the lower portion is filled
in. The exhaust ports are circular in cross section and radically
raised compared to a 4V exhaust port so custom headers are required
(available off-the-shelf for Panteras). The A3's have the largest ports
of the lot (241 cc intake and 134 cc exhaust) and were optimized for 355
cid and larger engines used in drag and circle track racing. The B351's
came on the scene next. They had smaller 223 cc intake and 106 cc exhaust
ports and were optimized for NASCAR 355's. The C302's were the final
version of these heads and had the the smallest ports (212 cc intake and
95 cc exhaust, optimized for 320 cid and under Trans Am engines). They
were also designed to permit (require) custom porting for larger displacement
applications.

Since this family of heads was originally based upon iron 4V heads, they
are compatible with Boss 302, Boss 351, and 351 SVO valvetrain components
and pistons. Except for the intake and exhaust manifold differences
that are required by the port location and shape differences, these heads
were designed to be 1-for-1 replacements for Boss 351 cylinder heads.
They use a Cleveland style quench chamber and standard 302 Boss/351
Boss/351C/351 SVO valve train parts (will accept 2.19"/1.71" valves).
They have cast iron seats and guides (titanium valve compatible) and are
set up for studs and guide plates. They are also cast with combustion
face and front and rear coolant outlets to allow use on Windsor, Cleveland,
and SVO blocks. Pipe plugs are provided to seal the threaded openings as
required. The fact that they are basically bolt-ons, unlike the Yates,
makes them very desirable heads, particularly for applications like Panteras
where off-the-shelf headers exist.

The earliest versions of these heads went by a "Phase" designation and
were originally referred to as Phase 1 (A3), Phase 1 3/4 (B351), and Phase
III (C302, D302) heads. I also have a set of A3 heads that are Phase 1 1/2
that have intake ports that are narrower (look more like the B351 ports)
than other A3 heads. The exhaust side appears to be standard A3.
Apparently, these variations are not unusual as there were various versions
of these heads cast for specific applications and race teams. There were
also minor variations of the these heads. For instance, the D302 was an
unmachined version of the C302.

Roush and Edelbrock cast a variety of aluminum single plane race intakes
for the early high port heads.

Some other notes:

1. The M-6049-A3 head has the largest intake port volume (241 cc's)
and exhaust port volume (134 cc's), intake flows 280 cfm @ 25 in Hg
as cast, doesn't respond to rpm transitions as well as B351 or C302,
has slight bend on intake port wall to accomodate pushrods, raised
floor increases port radius, straightening the turn for incoming
mixture and minimizing fuel separation, optimized for 355 and larger,
drag racing, circle track, etc.

2. The M-6049-B351 has intermediate port volumes (223 cc's intake,
106 cc's exhaust, flows 260 cfm @ 25 in Hg as cast, intake port
wall filled around pushrod area to straighten it, intake floor same
as A3, material added to exhaust port floor increasing radius for
flow, optimized for NASCAR.

3. The M-6049-C302 has the smallest port volumes (212 cc's intake,
95 cc's exhaust), at the radius the intake port floor has been
filled about 0.120" which forms a slight hump to lift incoming
mixture and drop it evenly around the valve, like B351 wall filled
around pushrod to ensure straightness, optimized for Trans Am 320
cubes and under, narrow ports for increased velocity.

4. B versions (M-6049-C302B, M-6049-D302B) were revised for durability
but not approved by NASCAR, advertised as "too hot for NASCAR" by
SVO, extra material in rocker pedestal area and at spring seats,
rocker cover raised 0.2", improved heat treat, shoulder added to end
plug for improved sealing, outer bolt boss height raised to provide
common head bolt length.

5. All versions are fully compatible with 302 Boss/351 Boss/351 SVO
valve train parts (will accept 2.19"/1.71" valves) and have cast
iron seats and guides (titanium valve compatible), rocker stud
pedestals are machined flat and holes are tapped for threaded studs
and guide plates.

6. Uses Motorcraft AG-series spark plug (14 mm, 3/4 inch reach) with
gasket.

7. Head is cast with combustion face and front and rear coolant outlets
to allow use on 351W and 351C blocks. Pipe plugs are provided to
seal openings as needed. On Clevelands, install pipe plug in holes
on end of heads.

8. Originally referred to as Phase 1, 1 1/2, 1 3/4, and III heads.

9. Brodix has recently introduced a bolt-on replacement for the C302B head.

10. Nominal combustion chamber volume for the high port heads is usually
listed at 62 cc's, though Ford Motorsport sometimes lists 65 cc's.

11. Special versions of these heads were made for certain race teams.
I have a set of narrow intake port A3's, for instance.

Other stuff you may or may not know about, high port heads require one inch
longer head bolts/studs (use hardened washers). A3's, B351's, and early
versions of the C302 heads had one short bolt. Later C302B's got common
length bolts. The high port heads come with combustion face and front and
rear coolant outlets which get plugged with aluminum pipe plugs as needed.
Where the plugs go is a function of the block, whether or not the intake
has a coolant cross-over, and whether or not you run a remote coolant cross
-over. For instance, if you put high port heads on a Windsor style block
with a coolant cross-over manifold, the plugs go in the ends and the
combustion face and a 0.8" hole is drilled at the coolant cross-over.
The supplied instructions illustrate the options. Use a thread sealer and
make sure the plug is below or level with the deck surface. On Cleveland
blocks, pipe plugs go in the holes on the ends of the heads (coolant goes
from block to head, intake is dry). Also an external (not in manifold)
coolant crossover can be used (M-85920A351) to take water out the front of
the heads.

> Are these cosidered a good head as well?

"Beevis, there's no such thing as bad head"

Dan Jones