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Full Version: The differences between US heads & the Aussie heads?
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There are both closed and open chamber Aussie 2V heads. The
ones of interest are the closed chamber versions that are usually
sourced from Aussie *302* Clevelands (351C blocks with 3" stroke
cranks and 6.02" rods). I'm not sure if they were used on any
Aussie 351C's. At least one Mustang magazine has reported these
heads have 10% larger intake ports (versus U.S. 2V) but I have not
found that to be the case. The open chamber Aussie 2V heads are,
for all intents and purposes, the same as U.S. 2V heads. Later
Panteras equipped with Aussie 351C's used these low compression
heads. The Aussies also had 4V heads sourced from the States for
a time.

Production Cleveland heads differ in 3 primary respects: combustion
chamber design, port shape/volume, and valve size. The short answer
is the Aussie 2V quench heads combine the high compression chamber
of the early 4V engines with the better balanced ports of the 2V
head. For the long answer, read on.

There were two basic combustion chamber designs - closed (also
referred to as quench) and open. The closed chamber heads have
smaller combustion chambers (62 to 66 cc's for 4V quench, 55 to 59
cc's for Aussie 2V quench), characterized by a large flat area (the
quench area) opposite the spark plug. As the piston travels towards
the chamber, mixture in the quench area gets compressed more quickly
than the mixture in the rest of the chamber. As Jack DeRyke described
in an earlier posting "this 'squirts' the mixture out of the closing
gap between the piston & head with high velocity. The resulting
swirl/mixing homogenizes the mixture better right around the plug,
the 'burn' is more complete and more power results". The quench
effect also tends to cool hots spots, averaging temperatures in the
chamber. Note that to optimize the effect, the piston should be a
flat top (in the quench area) and needs to get fairly close to the
chamber, within 0.040" (static) according to the Keith Black Pistons
tech page. When computing this distance, remember to include the
compressed thickness of the head gasket and the deck clearance (the
distance your piston is down in the bore). Cleveland quench heads
are rather resistant to pre-ignition and can tolerate 11:1 compression
ratios with a typical performance cam grind. They also require less
total spark (an important measure of chamber efficiency) than open
chamber heads.

Open chamber heads were introduced for emissions reasons and to
lower compression ratios to match the lower octane fuel of the
early 1970's. One undesirable consequence of the quench chamber
is that the flame front is prematurely extinguished as it travels
across the chamber, resulting in unburned mixture and increased
emissions. Open chamber heads, lacking the quench area, do not
have this problem so they burn cleaner. They also shroud the valves
less, increasing flow a bit but not nearly enough to offset the
loss of the quench effect. Open chamber heads are also less
tolerant of high combustion ratios with 10:1 (requires a pop up
piston to offset the larger chamber volume) being the suggested
maximum. They also require more spark lead since the flame front
has to travel across the larger chamber). Vizard claims open
chamber heads respond well to multiple spark ignitions (e.g. MSD 6),
requiring less ignition lead.

The bottom line is that quench heads are the best pick for high
performance applications. Both 2V (Aussie 302C) and 4V ('70 and
'71) heads are available with quench chambers.

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
seriously 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 like a lot of lift and keep flowing more air past
0.600" valve lift.

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 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 short side radius. Though much smaller in cross-sectional
area, the port flows as much as a 4V, with substantially higher
velocities. Since the heads have a good intake to exhaust flow ratio,
they don't require the exaggerated dual pattern cams like the 4V. 2V
heads also have good low lift flow but, in unported form, don't flow
much more once 0.500" valve lift is exceeded. Why Ford didn't use the
2V exhaust port on the 4V is beyond me. It still cleared the early
shock towers.

To match their larger ports, early 4V heads have larger 2.19"/1.71"
valves. 2V heads were fitted with smaller 2.04"/1.65" valves. For
some reason, it appears some later open chamber heads were fitted with
the smaller 2V valves. Since the valve spacing is identical between 2V
and 4V heads, one can install larger (but heavier) 4V valves in the 2V
or late 4V heads. The second hand information I have indicates that
ported 2V heads can benefit from a larger intake but a larger exhaust
is not necessary. FPP and others offer an stainless steel oversize
2.08" intake valve that might work well.

Another minor difference between 2V and 4V heads, at least the ones
I've examined, is a lack of webbing near the rocker arm pedestals.
It looks like it would promote oil drain-back but might weaken the
head a little.

Also, Boss 351 and HO 4V heads were set up with adjustable valve train
(milled pedestals, studs, and guide plates) from the factory, though
any Cleveland can be converted.

>Where would be the best place to get a set and how much should be
>shelled out for a set.

I bought one set at the Pomona swap meet for $200 and another set from
Mike Fielder for $300. Both pair were fresh out of an Australian
junkyard and covered in grease and mud. It turned out one head was
cracked but Mike made good on it. Mike moved back to Australia but
he's got some deal going with someone in California to sell his stuff.
I had a card with the names and numbers but I can't seem to locate it
at the moment.

Others I've seen advertising Aussie heads are:

Brent Alexander
714 Fairview
Boonville, IN 47601
$375/pair bare, crack tested

Ford Power Parts

Perogie Enterprises

P.C. Automotive
$875 complete and assembled
$1095 ported and flowed
7/16" screw-in studs with guide plates
stainless steel valves
solid bronze guides
115 lb springs
hd retainers and locks

>Should a guy/gal decide to use a set should he/she use a 2V intake and
>smaller diameter primary exhaust tubes??

Yes, while you can bolt 4V intake manifolds and exhaust headers to
a 2V engine, the ports are different enough to warrant unique parts.
When I built my engine, I had an Edelbrock F-351 2V (same as a
Performer 2V) dual plane, a Holley Street Dominator (p/n 300-12)
single plane, and a Weiand Xcelerator (p/n 7516) available. The
Street Dominator has a small plenum and ports that are smaller than
those of the head. One interesting thing about the Street Dominator
is that it has a trapezoidal carb base and will bolt up the stock
Pantera spreadbore Motorcraft 4300D carb. The Edelbrock ports matched
the size of the head ports. The Weiand ports and plenum were largest
of all. They were essentially pre-ported and require the heads be
match ported to the intake. Since, it looked like the highest
performing piece of the bunch, I ended up going with the Weiand and
like it a lot. Pulls strong and smooth from right off idle. Offy also
makes several intakes for the 2V heads including the Dual Port which
Kirby put on his Longchamp for better low end (replaced a Street
Dominator IIRC), Equa-Flow (split plenum single plane), Port-o-Sonic
(open plenum single plane), and Dial-a-Flow (open plenum single plane
with bolt in plenum stuffers). If you go to Asa Jay's homepage, you'll
find a fairly complete list of intakes available for the 2V and 4V
heads. That reminds me, did the Aussies have any aluminum intakes?
I was surfing the web and I came across some info that implies they ran
Carter Thermoquads on their 351's for a few years. Can anyone confirm
this? I had previously heard it was Quadrajets.

On the exhaust side, I'm running Hedman Pantera headers from Larry
Stock. These have the proper 2V flange with 1 3/4" primaries, 29"
long, and a 2 1/4" collector (for GTS tailpipe compatibility). 4V
headers will also bolt up but they're likely to be to large for best
results. To fit the large 4V exit area, most 4V headers are 1 7/8"
diameter or larger. The GTS tri-y is 2".

You'll also want to pick a cam to fit the 2V flow characteristics.
They'll work fine with a single pattern but I went with a Cam Research
custom grind (cam and lifters around $150) because I couldn't find
exactly what I wanted. I ended up going with a slight dual pattern
(218/222 degrees duration @ 0.050") to compensate for the exhaust
restriction of the mufflers and tailpipes.

Steve Stone down under says that 2V heads are a dime a doz, and they
can be had for around $20. I am having a difficult time believing one
can get any thing good for $20 now a days.

Supply and demand. They're a common junkyard part down under, just
like open chamber 2V heads are here (about $75/pair last I checked).
Plus the exchange rate between Australia and the U.S. is favorable for
importing from Oz.

He did go on to mention shipping would run well over a couple of
$100 bucks. Sorry for run on questions.

From talking with Mike Fielder, I gather he waits until he gets a
large enough order that he can fill a cargo container of some sort.
You might want to have the heads clean and crack tested before